Data Dictionary

All GIS layers use the following projection information:
Projection - Lambert Conic Conformal
Coordinate system - Maryland Stateplane
Zone - 4126
Datum - NAD83
Units - Feet
Spheroid - GRS1980

Cover: CONTR
Theme: PLANIMETRIC & TOPO
Source: LIGHT DETECTION AND RANGING (LIDAR) Flown March, 2001
Describe: TOPOGRAPHIC CONTOURS, TWO (2) FOOT

Topographic coverage is derived from the digital elevation data taken March 2001. Index contours, intermediate contours are presented and index contours are appropriately labeled. The coverage is stored as an Arc Attribute Table (AAT).

The countywide topography was interpolated using Surfer point interpolation software. The input files were variably spaced Lidar data that were re-sampled to produce a smooth 10 ft -by-10 ft digital elevation model (DEM) grid.

Topographic contour lines were developed at two-foot intervals using Terramodel’s contour interpolation module. The contour generation module automatically generates contour lines from the 10 ft -by-10 ft DEM grid points obtained through stereo-compilation.

Index contours are generated at every fifth contour. Intermediate contours represent the four topographic lines between index contours. Intermediate and index contours are stored as visible lines in an ARC/INFO AAT file. The elevations for all contour lines will be stored in a three-position integer item called ELEVATION.

Accuracy:
RMSE = 16.1 cm
NSSDA = 1.03’ (95% confidence level)
VMAS = 0.87’ (90% confidence level)

7101 - index contour
7102 - intermediate contour
7103 - index depression contour
7104 - intermediate depression contour

Cover: BRIDG
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY, March, 2000
Describe: BRIDGE & TUNNELS (PLANIMETRIC)

COVERAGE DERIVATION:

This coverage includes bridges and tunnels as extracted from aerial photography conducted Spring, 2000. Bridge lines were further subdivided into end segments and non-end segments. Tunnels include annotation labeled as "TUNNEL".

Location: L:\PGCO\LAYERS\2000\LIB\<200SHEET>\BRIDGE
File size: Approximately 12.4KB
Created: Buchart-Horn, Inc.
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: BUILD
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (March, 2000)
Describe: BUILDING FOOTPRINT (ROOFLINE)

COVERAGE DERIVATION:

The countywide building footprint information was stereo-photogrametrically captured and compiled at a 1 inch=200 foot scale using geodetic control and 1" = 1,200 foot scale aerial photography taken in Spring, 2000.

PLANIMETRIC CAPTURE SPECIFICATIONS:

The building layer will be stereo-photogrametrically captured from digital orthophotography. The term commonly used for this planimetric layer is building footprints. In actuality, the true building footprint cannot be gleaned from aerial photography and so the capture of buildings is more or less confined to the capture of rooflines.

All structures with roofs having an aerial coverage of 200 square feet or greater will be captured from the photography. Buildings will be delineated by tracing the apparent edge of the roofline for dwellings, businesses, houses, house trailers, garages, and barns. Where appropriate, buildings will be squared at the corners so that the corners are orthogonal and within the established mapping accuracy tolerance for 1:2400 scale mapping.

Interior rooflines, such as dormers, will not be captured. Roofline extensions, such as carports, decks, patios, stairs, etc. will not be captured or shown.
The building layer should be a seamless cover with no buildings being split for some imposed sheet tiling. Those buildings found at the edge of the model (at the Prince George's/Montgomery County boundary or the Prince George's/Washington D. C. boundary) should be shown in their entirety.

All building polygons should show proper closure and contain one pseudonode. The vectorized building roofline should very closely fit the building rooflines displayed on the digital orthophotography. Those buildings under construction and ruins were also captured. Annotation was labeled as "U/C" and "RUIN" as appropriate for these features.

Location: L:\PGCO\LAYERS\2000\lib\<200SHEET>\BUILD
File size: Approximately 400KB
Created: Buchart-Horn, Inc.
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

2201 - building
2202 - ruin
2203 - building under construction
2204 - trailer home
2301 - not a building

2101 - neatline
2102 - project boundary
2103 - building line
2104 - ruin line
2105 - building under construction line

Cover: CULTRL
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (March, 2000)
Describe: CULTURAL FEATURES

COVERAGE DERIVATION:

This coverage includes athletic fields/courts, cemeteries, golf courses, fences, landfills, retaining walls, noise barriers, swimming pools, sand and gravel sites, storage tanks, and smokestacks. The features were extracted from aerial photography flown Spring, 2000.

Athletic Field/Court or Golf Course: Areas delineated by the apparent boundary of the feature only where not bounded by a fence or other linear feature. Annotation labeled for each feature as "ATHLETIC FIELD," "TENNIS COURT," "GOLF COURSE", etc as appropriate. Annotation is within the feature and follows positional angle of the feature.

Cemeteries: Areas delineated where obvious on the aerial photography. Annotation labeled for each as "CEMETERY."

Fences: All fences greater than 1000 feet in length and visible on the aerial photography were captured as a single line.

Landfills: All currently operating public waste disposal landfills were captured. Annotation labeled as "LANDFILL" was placed within each feature.

Retaining Wall: Three types of retaining walls were captured:
1. Retaining Wall at Edge of Water - fixed structure of concrete, brick, stone, etc. that retains earth at water edge. Walls were delineated and annotation labeled as "RW."
2. Retaining Wall not Part of Road System - fixed structure of concrete, brick, stone, etc. retaining earth, usually along driveways or parking lots. Delineated if greater than 200 feet in length and annotation labeled as "RW."
3. Retaining Wall Part of Road System - fixed structure of concrete, brick, stone, etc. retaining earth adjacent to, and parallel with a road or railroad edge. Walls were delineated and labeled as "RW."

Noise Barrier: Structures of at least 200 feet in length that run parallel to a major highway were delineated as a single line and annotation labeled as "NOISE BARRIER." Annotation follows positional angle of the feature.

Sand and Gravel Site: All visible sand and gravel sites were delineated and annotation labeled as "SAND" or "GRAVEL" as appropriate.

Storage Tank and Smokestack: All visible storage tanks and smokestacks were captured at the apparent base of each feature. Annotation was labeled as "STORAGE TANK" or "SMOKESTACK" as appropriate.

Swimming Pools: All apparent public swimming pools were delineated and annotation labeled as "POOL" for each feature.

Location: L:\PGCO\LAYERS\2000\lib\<200SHEET>\CULTRL
File size: Approximately 400KB
Created: Buchart-Horn, Inc.
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

6201 - Athletic Field
6202 - Cemetery
6203 - Golf Course
6204 - Landfill
6205 - Major Retaining Wall (NOTE: No features at this time)
6206 - Public Swimming Pool
6207 - Sand / Gravel Site
6208 - Tank / Smokestack
6209 - Dam
6301 - Not a Cultural Feature

6101 - Athletic Field
6102 - Cemetery
6103 - Dam
6104 - Fence
6105 - Golf Course
6106 - Landfill
6107 - Major Retaining Wall
6108 - Noise Barrier
6109 - Public Swimming Pool
6110 - Sand / Gravel Site
6111 - Tank / Smokestack
6112 - Neatline
6113 - Project Boundary

Cover: TRANS
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (MARCH, 2000)
Describe: TRANSPORTATION FACILITIES OTHER THAN ROADS, RAILS & BRIDGES

This coverage contains various transportation-related planimetric features. This includes roadways, parking lots and airports. Annotation subclasses are defined for parking, airport and runway.

The countywide edge of paving information was stereo-photogrametrically captured and compiled at a 1 inch = 200 feet scale using geodetic control and 1:14,400 scale aerial photography taken in March, 2000. In addition to roadway edge of paving, paved parking areas were captured if the area encompassed was approximately 200 square feet or more. Medians greater than twenty feet wide for a length of 50 feet or more were also stereo-photogrametrically captured.

The edge of paving is defined as the edge of an improved surface roadway, including the shoulder of that road, if that road is paved with either asphalt or concrete. Gravel shoulders are not captured. Sidewalks are not included in the pavement edge regardless of their proximity to the edge of the roadway pavement. Road polygons are typically split at intersections with other roads and the area is equally distributed to the road polygons through a process called triangulation.
Dirt or gravel roads and private paved roads that are obviously regularly traveled by the general public will also be captured according to their apparent edge of traveled surface. Private driveways, paved or unpaved will not be captured. When the edge of pavement is obscured by other structures such as bridges, overpasses or the road is entering a tunnel, the edge of paving will be approximated as a straight line connecting the apparent entrance and exit points of the continuing pavement feature and categorized as a hidden road.

Paved or unpaved parking lots with a capacity of ten or more cars (about 200 square feet), or greater than 50 feet in length, were captured as parking lot polygons and graphically labeled as "PARKING." Division between parking lot polygons and road polygons were determined by continuing a straight line from curb to curb at the entrance to the parking lot, or by a straight line continuation of the apparent edge of pavement. Parking lots that completely surround buildings will be digitized as parking lots with coincident lines for the building roofline. The APS software will isolate the building roofprint so the acreage or square footage of the parking lot is accurate. All lines or polygons that intersect building rooflines were snapped to the roofline using the proprietary software. In this way, there are no overlaps, undershoots, or gaps present.

Large medians or landscaped islands greater than 500 square feet were captured. Proprietary software will be used to separate the islands to ensure accurate aerial measurements. All land between divided highways and roads, as well as traffic circles, were captured as medians.

All paved surfaces used for aircraft takeoff, landing, or taxiing will be recorded as polygons and graphically labeled as runways. All structures greater than 2000 square feet in aerial coverage will be digitized as building features. The apparent perimeter of the airfield, whether large or small, will be recorded as a linear feature and graphically labeled AAIRPORT@ unless bounded by a fence of a previously captured feature.

Sidewalks were captured as a single line feature at the center of each. Only those sidewalks along public roads were captured.

Includes major dirt passageways, permanent in nature, usually in rural or undeveloped areas. Trails are either cross-country trails or used as a service trail/road (e.g. running along railroad tracks, connecting transmission towers, providing access to water pumping station). Trails are usually distinguishable from unpaved roads by lack of maintenance. Delineated as a single line with annotation labeled as "TRAIL" following the positional angle of each feature.

1201 - street
1202 - parking
1203 - airport
1204 - median
1205 - unpaved parking
1301 - non-transportation feature

1101 - neatline
1102 - project boundary
1103 - paved road
1104 - unpaved road
1105 - paved parking
1106 - unpaved parking
1107 - airport
1108 - runway
1109 - median
1110 - closure line
1111 - link line
1112 - Sidewalk / Walkway
1113 - Trails

Cover: UTILT
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (MARCH, 2000)
Describe: MAJOR TRANSMISSION LINES AND SUBSTATIONS

COVERAGE DERIVATION:

This coverage includes major transmission lines for those power lines supported by steel towers with four legs. The lines are shown as well as the outlines of the towers. Other transmission lines were captured if supported by towers made of wood or metal with two legs or multiple, non-parallel support arms, and if readily visible in the aerial photography. In addition, transformer stations, which include high voltage units within fenced enclosures, were delineated. Annotation was labeled as "SUBSTATION" for each.

Location: L:\PGCO\LAYERS\2000\LIB\<200SHEET>\UTILT
File size: Approximately 1.07KB
Created:Buchart-Horn, Inc.
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

10101 - substation
10102 - transmission line
10103 - neatline
10104 - project boundary

Cover: VEGET
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (MARCH, 2000)
Describe: SIGNIFICANT VEGETATION

COVERAGE DERIVATION:

Wooded areas greater than 10,000 square feet in aerial coverage were captured from aerial photography conducted Spring, 2000. These features were captured as polygons and divided into 2 subclasses, Tree Cover and Dense Tree Cover. Wooded areas dominated by coniferous vegetation were captured as Dense Tree Cover, while wooded areas dominated by deciduous, broadleaved trees were captured as Tree Cover.

Tree Cover areas were labeled with "TREE COVER" annotation, while Dense Tree Cover areas were labeled with "DTREE COVER" annotation. Trees in wooded areas captured averaged at least eight feet in height. The perimeter of a wooded area was delineated by a generalized line along the outside edge of most tree trunks.

All wooded areas split by roads, where the woodland canopy is noticeably split, were shown as being split into two separate polygons by an edge-of-road polygon. Single trees having a crown spread less than 10,000 square feet were not captured. Land use types (i.e., pasture land, agricultural fields, open fields, etc.) outside of the wooded area were not separately identified or graphically labeled.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\VEGET
File size: Approximately 74.2KB
Created: Buchart-Horn, Inc.
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: BRIDG
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY, April, 1993
Describe: BRIDGES & TUNNELS (PLANIMETRIC)

This coverage includes bridges and tunnels as extracted from aerial photography conducted April, 1993. This planimetric coverage is presented as meeting National Map Accuracy Standards at a scale of 1:24,000. Both AAT and PAT files are included in the coverage as in annotation.
Note: GeoMaP specification included major culverts. In Prince George's County, hydrologic structures are stored in a separate coverage (HYDRS).

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\BRIDGE
File size: Approximately 12.4KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: BUILD
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: BUILDING FOOTPRINT (ROOFLINE)

COVERAGE DERIVATION:

The countywide building roofprint information was stereo-photogrametrically captured and compiled at a 1 inch=200 feet scale using geodetic control and 1:14,400 scale aerial photography taken in April, 1993. The coverage is stored as both an Arc Attribute Table (AAT) and as a Polygon Attribute Table (PAT). Annotation Subclasses exist for ruins and buildings under construction. Annotation features are represented with symbol 2.

PLANIMETRIC CAPTURE SPECIFICATIONS:

The building layer will be stereo-photogrametrically captured from digital orthophotography. The term commonly used for this planimetric layer is building footprints. In actuality, the true building footprint cannot be gleaned from aerial photography and so the capture of buildings is more or less confined to the capture of rooflines. All structures with roofs having an areal coverage of 200 square feet or greater will be captured from the photography. Buildings will be delineated by tracing the apparent edge of the roofline for dwellings, businesses, houses, house trailers, garages, and barns. Where appropriate, buildings will be squared at the corners so that the corners are orthogonal and within the established mapping accuracy tolerance for 1:2400 scale mapping.

Interior rooflines, such as dormers, will not be captured. Roofline extensions, such as carports, decks, patios, stairs, etc. will not be captured or shown. The building layer should be a seamless cover with no buildings being split for some imposed sheet tiling. Those buildings found at the edge of the model (at the Prince George's/Montgomery County boundary or the Prince George's/Washington D. C. boundary) should be shown in their entirety. All building polygons should show proper closure and contain one pseudonode. The vectorized building roofline should very closely fit the building rooflines displayed on the digital orthophotography.

All building coverages will be processed through the QC AML's (Arc Macro Language) developed by Maxima. These AML's test for the presence of appropriate subdirectories that are created by ARC/INFO (i.e., .pat, .aat, .nat, etc.), give a description of the coverage, test for tic and bnd agreement with the master grid, check for labelerrors, and describe feature coding and annotation present in the building layer. The coverage is then visually checked for building addition or deletion by overlaying the building coverage on the appropriate digital orthophoto tile. Errors are reported on hard copy composite planimetric plots that are available for each tile layer. Results of this QC effort are maintained by the GIS coordinator in a series of three ring binders. All data tiles are checked in this fashion. The resulting coverages are 100% accurate for buildings that met the criteria for capture as of the date of the aerial photography April 1993.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\BUILD
File size: Approximately 400KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

2201 - building
2202 - ruin
2203 - building under construction
2301 - not a building

2101 - neatline
2102 - project boundary
2103 - building line
2104 - ruin line
2105 - building under construction line

Cover: CONTR
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY, APRIL 1993
Describe: TOPOGRAPHIC CONTOURS, FIVE (5) FOOT

Topographic coverage is derived from the digital elevation data taken April, 1993. Index contours, intermediate contours are presented and index contours are appropriately labeled. The coverage is stored as an Arc Attribute Table (AAT). Annotation subclasses are defined for standard index labels (reg-label) and depression labels (dep-label) using ARC/INFO symbol 8 at a height of 20.0.

The countywide topography was interpolated, using the WILD Contour Interpolation Program, from digital elevation data that was stereo-photogrammetrically compiled using geodetic control and 1:14,400 scale aerial photography taken in April, 1993.

Topographic contour lines will be developed at five foot intervals using WILD's Contour Interpolation Program (CIP). The CIP will automatically generate contour lines from points obtained through stereo-compilation. Spot elevations along with index, intermediate, index depression, and intermediate depression contour lines will be delineated. Figure 1A-D gives a generalized version of the capture of spot elevations, the building of a digital elevation model, and the interpolation of the various contour line types.

Where contour lines disappear under buildings, bridges, culverts, or into dense vegetation, hidden contours will be created to maintain contour connectivity. Hidden line contours will be snapped to the appropriate visible line contours in all instances. Snapping lines means there will be no overshoots, undershoots, or unconnected linework.

Index contours will be compiled at every fifth contour. The index contours will be graphically labeled approximately every 6 to 12 inches (every 1200 to 2400 feet at map scale) as measured along the contour line to be labeled. All index contours will be labeled with their elevation given in full feet. All index contours will be graphically labeled at least once per line crossing a sheet model. This labeling will not be done in a regular pattern and, where possible, will be in diagonal stacks and will read uphill.

The index contours will also be stored as visible and hidden lines in an ARC/INFO AAT file. It will be necessary to identify eight different types of lines within a linetype attribute item. Table 1 identifies the coding to be used for each linetype. The elevations for all contour lines will be stored in a three position integer item called ELEVATION.

Intermediate contours will represent the four topographic lines between index contours. Intermediate contour lines will not be graphically labeled but will have a linetype attribute coded according to the designated codes and will have an appropriate elevation attribute associated with each intermediate contour line.

A depression contour is a contour which closes within the mapping limits, or which obviously closes outside the stereomodel limits, where the area inside the contour is lower in elevation than the contour where the depression starts. There are two types of depression contours: index and intermediate. Index depression contours will be graphically labeled in full feet according to the same rules applied to index contours. Intermediate depression contours will not be graphically labeled. Hidden line attributes will be as specified in the code table and depression contour elevations will be stored in a three-position item called ELEVATION.

NOTES: ELEVATION and LAB-SEG values are added items. The ELEVATION item stores the three digit elevation value, LAB-SEG is used to denote hidden contour lines (lines under buildings, bridges, etc.), and FTR-CODE is used to differentiate index and intermediate contour line types.
Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\CONTR
File size: Approximately 464KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format:Arc/Info Coverage 8.x Format
Data structure:

7101 - index contour
7102 - intermediate contour
7103 - index depression contour
7104 - intermediate depression contour
7105 - hidden index contour
7106 - hidden intermediate contour
7107 - hidden index depression contour
7108 - hidden intermediate depression contour

Cover: HYDRA
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL 1993)
Describe: PLANIMETRIC HYDROLOGY (STREAMS WIDTH OF 20' OR MORE)

There is a set of coverages which present hydrologic features in the County:
Streams of 20 feet or less are represented in the HYDRL coverage.
The centerline for all streams (regardless of width) are represented in the hydrologic centerline coverage, HYDRC.
Hydrologic structures are represented in the HYDRS coverage.

This particular coverage contains streams 20 feet or wider.

This coverage contains the drainage area where the width of the identified feature is 20 feet or more as photointerpreted from aerial photography. The coverage is stored as an Arc Attribute Table (AAT) and as a Polygon Attribute Table (PAT). Annotation has been defined for swamp (standing water), reservoir and lake. Each feature is represented in the annotation using ARC/INFO symbol 2. Lakes, Ponds and Standing Water.

All lakes and ponds with a visible and distinct shoreline and having an aerial coverage greater than 20,000 square feet will be captured as polygons. The shoreline for these features is based on the water surface elevation when the aerial photography was taken and may not represent the normal pool elevation for the feature. The water surface elevation will be graphically labeled at or near the centroid of the feature.
Areas of standing water, which may or may not be interspersed with areas of vegetation and which do not have a visible water impoundment structure will be outlined and labeled as ASTANDING WATER.@

Bodies of water with an average width greater than or equal to 20 feet at ground scale will be captured as double line and stored with both polygon and line attributes. Streams with an average width of less than twenty feet will be shown as a single line and stored as an attributed line.

Culverts greater than 50 feet in length and which carry rivers or streams under roads or railroads will be captured as a straight line connecting the apparent points where the stream or river enters and exits the culvert. Concrete structures such as head walls, wingwalls, and/or end sections will be shown if they are greater than 50 feet in length. Man made barriers erected across a stream to prevent or regulate the flow of water will be captured and labeled as ADAM.@

Man made drainage basins, or reservoirs, are designed to store water runoff in order to recharge the ground water supply. These basins will be captured as linear features and labeled as ARESERVOIR@ only when visible from the photography, are greater than 10,000 square feet in aerial coverage, and are not bounded by fencing or other linear features. Man made drainage channels will be shown if they are greater than 200 feet in length and if visible on the aerial photography.

All other hydrologic features not expressly described in these specifications will be connected by straight lines during the graphic workstation editing phase. This will be done in order to maintain a continuous network.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\HYDRA
File size: Approximately 12.0KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

4201 - pond/lake
4202 - swamp (standing water)
4203 - reservoir
4204 - double line river
4205 - double line drain (stream)
4207 - any hidden double line feature
4301 - non-water

4101 - neatline
4102 - project boundary
4103 - pond/lake
4104 - swamp (standing water)
4105 - reservoir
4106 - water link line
4107 - double sided river line
4108 - double sided drain line
4110 - double sided hidden drain line

Cover: HYDRC
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: PLANIMETRIC STREAM CENTERLINES

The countywide water centerline information was derived from the countywide plan-hydro coverage using ASI's APS software. This coverage was compiled using geodetic control and 1:14,400 scale aerial photography taken in April, 1993. The coverage is stored in an Arc Attribute Table (AAT) and as a Node Attribute Table (NAT).

Stream centerlines will be captured as a separate layer and as a useable ARC/INFO network,. Where steams are single line features, those lines will be considered as centerlines. Where streams are double line features, centerlines will be derived as the midpoint of the distance between the two stream or river banks. The centerline network will be appropriately directional and will have line and node attributes according to the feature code designations for the .NAT file in ARC/INFO.

NOTES: Water body names are found in the roadway centerline file under water-name.

(1) If an origin node shares a location with any other type of node, the FTR-CODE for the shared node will represent the type of entity beginning at that location, not an origin node.

(2) Dam or weir node FTR-CODEs will take precedence over any other type of node that may share the same location.

(3) There will be a note assigned with all arc (i.e., structure, body of water) that cannot be connected to the continuous drainage. This note will indicate that the entity was reviewed and that an interpreted connection could not be made to the continuous drainage.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\HYDRC
File size: Approximately 3.16KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

0 - unknown
12100 - origin of drainage centerline
12101 - confluence of two or more centerlines
12102 - divergence of centerline into two or more centerlines
12103 - dam
12104 - weir
12105 - inlet to body of water
12106 - outlet from body of water
12107 - upstream side of bridge
12108 - downstream side of bridge
12109 - upstream side of culvert
12110 - downstream side of culvert
12111 - water connectivity node

12001 - visible drainage centerline (includes structures)
12002 - connectivity drainage centerline (interpreted of connectivity)
12003 - hidden drainage centerline

(1) If an origin node shares a location with any other type of node the FTR-CODE for the shared node will represent the type of entity beginning at that location, not an origin node.

(2) Dam or weir node FTR-CODES will take precedence over any other type of node that may share the same location.

Cover: HYDRL
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: PLANIMETRIC STREAMS (WIDTHS OF LESS THAN 20')

There is a set of coverages which present hydrologic features in the County:
Streams of 20 feet or less are represented in the HYDRL coverage.
Streams 20 feet or wider are represented in the HYDRA coverage.
The centerline for all streams (regardless of width) are represented in the hydrologic centerline coverage, HYDRC.
Hydrologic structures are represented in the HYDRS coverage.

This particular coverage contains the drainage lines for streams of less than 20 feet. The features are stored in an Arc Attribute Table (AAT).

Stream centerlines will be captured as a separate layer and as a usable ARC/INFO network. Where streams are single line features, those lines will be considered as centerlines. Where streams are double line features, centerlines will be derived as the midpoint of the distance between the two stream or river banks. The centerline network will be appropriately directional and will have line and node attributes according to the feature code designations for the .NAT file in ARC/INFO.

NOTES: Water body names are found in the roadway centerline file under water-name.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\HYDRL
File size: Approximately 2.57KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

8002 - natural waterway (single sided stream)
8005 - hidden waterway (hidden single sided stream)

Cover: HYDRS
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: PLANIMETRIC HYDROLOGIC STRUCTURES

The countywide water centerline information was derived from the countywide plan-hydro coverage using ASI's APS software. The plan-hydro coverage was compiled using geodetic control and 1:14,400 scale aerial photography taken in April, 1993. Hydrologic structures are stored as an Arc Attribute Table (AAT). Only dams are represented by annotation (using symbol 2).

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\HYDRS
File size: Approximately 2.08KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: RAILR
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: RAILROAD LINES

The centerline of railroads apparently in active use; does not include metro rail lines. The features are stored as an Arc Attribute Table (AAT).

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\RAILR
File size: Approximately 1.07KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: SLOPE
Theme: PRINCE GEORGE’S COUNTY STEEP AND SEVERE SLOPES
Source: DEM, TOPOGRAPHY AND SPOT ELEVATIONS, 1993 data
Describe: TIN POLYGONS

This is a cover obtained from Advance Technology Solutions, Inc. (ATS) under a 1994 contract to create a countywide coverage for all slopes using the DEM data obtained from ASI in 1993 and 1994. The data was created using ARC/TIN and included percent slope to 0.1 percent, slope aspect, slope area, slope range and slope color for mapping.

Due to the size of the data files it was not practical to place all the data on the GIS. The 21 covers which comprised the county were each dissolved using the slope range attribute thus creating covers with four slope range categories. Two of those categories the steep slopes (15 to 25 percent slopes) and severe slopes (slopes greater than 25 percent) are used during environmental analysis of sites and are of particular importance.

Location: L:\PGCO\LIB1<200SHEET>SLOPE
File size: 2.7MB
Created: ATS
Modified: Environmental Planning Section
Contact: John Markovich (301)952-5404
Data format: Arc/Info Coverage 8.x Format

blank - slopes less than 15%
0 - internal polygons with slopes less than 15%
25 - slopes between 15% and 25%
90 - slopes greater than 25%

Cover: SPOTE
Theme: PLANIMETRIC &TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: SPOT ELEVATIONS

This coverage contains ground and water spot elevations stored in a Point Attribute Table (PAT). Annotation is defined for three subclasses, gnd_spot, non_cip_spot and wat_spot. Each uses ARC/INFO symbol 9 at a height of 20.0.

The countywide spot elevations were interpolated, using the WILD Contour Interpolation Program, from digital elevation data that was stereo-photogrammetically compiled using geodetic control and 1:14,400 scale aerial photography taken in April, 1993.

Spot elevations are collected during the data compilation phase for contour interpolation and are used to supplement the elevation data provided by contours. Spot elevations will be graphically labeled using a four digit, one decimal place label showing the data provided by contours. Spot elevations will be collected with special emphasis being placed at the following places:

1. All road and road/railroad intersections;
2. The apparent center of all bridges less than 200 feet long;
3. At the apparent high point or crown of the bridge instead of the center of the bridge, for bridges less than 200 feet long, and only where bridge is apparently higher at one end than the other;
4. At the apparent high point or crown of the bridge, in addition to the center of the bridge, if the bridge is greater than 200 feet long, and only where the bridge is apparently higher at one end than the other;
5. Along road and road centerlines at a sufficient interval to augment areas with little or no contours. For railroads, spot elevations will be recorded at the center of the railroad track cross-ties;
6. At the crest of all closed contours greater than one acre in size;
7. At the lowest point of closed depression contours, significant saddles, cuts, and depressions greater than one acre in size;
8. At the lowest point in pits and quarries and with sufficient frequency to define the character of the terrain within the pit or quarry;
9. At points of visible ground within areas of otherwise dense vegetation;
10. At sufficient intervals to augment areas with little or no contours;
11. At the top and bottom of cuts for rip-rap areas, as needed, to show terrain variation.

Spot elevations in areas other than those discussed above will be collected according to standard cartographic procedures. The M-NCPPC will be able to accurately derive spot elevations for other locations through the Digital Elevation Model (DEM), as required for specific applications.

Surface elevations will be shown for all water bodies captured. Surface elevations will be recorded at the apparent center of the water bodies such as ponds, standing water areas, or lakes. These water bodies will be labeled with a prefix of AWE@ followed by the elevation value to the nearest 1/10th of a foot.

Where double line streams have fewer than two contours crossing them, two surface elevations will be recorded for each stereomodel and labeled with AWE@ followed by the elevation value to the nearest 1/10th foot.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\SPOTE
File size: Approximately 39.1KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

11101 - CIP ground elevation
11102 - non-CIP ground elevation
11103 - water elevation

Cover: TRANS
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: TRANSPORTATION FACILITIES OTHER THAN ROADS, RAILS AND BRIDGES

This coverage contains the transportation and parking planimetric features. This includes roadways, parking lots and airports. The features are stored as both an Arc Attribute Table (AAT) and a Polygon Attribute Table (PAT). Annotation subclasses are defined for parking, airport and runway. Each uses ARC/INFO symbol 1.

The countywide edge of paving information was stereo-photogrametrically captured and compiled at a 1 inch = 200 feet scale using geodetic control and 1:14,400 scale aerial photography taken in April, 1993. In addition to roadway edge of paving, paved parking areas were captured if the area encompassed was approximately 200 square feet or more. Medians greater than twenty feet wide for a length of 50 feet or more were also stereo-photogrametrically captured.

The edge of paving is defined as the edge of an improved surface roadway, including the shoulder of that road, if that road is paved with either asphalt or concrete. Gravel shoulders are not captured. Sidewalks are not included in the pavement edge regardless of their proximity to the edge of the roadway pavement. Road polygons are typically split at intersections with other roads and the area is equally distributed to the road polygons through a process called triangulation.

Dirt or gravel roads and private paved roads that are obviously regularly traveled by the general public will also be captured according to their apparent edge of traveled surface. Private driveways, paved or unpaved, and trails will not be captured.

When the edge of pavement is obscured by other structures such as bridges, overpasses or the road is entering a tunnel, the edge of paving will be approximated as a straight line connecting the apparent entrance and exit points of the continuing pavement feature and categorized as a hidden road.

Paved or unpaved parking lots with a capacity of ten or more cars (about 200 square feet), or greater than 50 feet in length, will be captured as parking lot polygons and graphically labeled as AParking.@ Division between parking lot polygons and road polygons will be determined by continuing a straight line from curb to curb at the entrance to the parking lot, or by a straight line continuation of the apparent edge of pavement.

Parking lots that completely surround buildings will be digitized as parking lots with coincident lines for the building roofline. The APS software will isolate the building roofprint so the acreage or square footage of the parking lot is accurate. All lines or polygons which intersect building rooflines will be snapped to the roofline using the proprietary software. In this way, there should be no overlaps, undershoots, or gaps present.

Large medians or landscaped islands greater than 500 square feet will be captured. Proprietary software will be used to separate the islands to ensure accurate aerial measurements.

1201 - street
1202 - parking
1203 - airport
1204 - median
1205 - unpaved parking
1301 - non transportation feature

Cover: UTILT
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: MAJOR TRANSMISSION LINES

Major transmission lines supported by steel towers with four legs will be shown. Only lines and not towers will be shown. Other transmission lines may be captured if supported by towers made of wood or metal with two legs or multiple, non-parallel support arms, and if readily visible in the aerial photography.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\UTILT
File size: Approximately 1.07KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: VEGET
Theme: PLANIMETRIC & TOPO
Source: AERIAL PHOTOGRAPHY (APRIL, 1993)
Describe: SIGNIFICANT VEGETATION

Wooded areas greater than 10,000 square feet in aerial coverage were captured from aerial photography conducted April, 1993. These features were captured as polygons and labeled as ATREES.@ Trees in wooded areas captured averaged at least eight feet in height. The perimeter of a wooded area was delineated by a generalized line along the outside edge most tree trunks. All wooded areas split by roads, where the woodland canopy is noticeably split, will be shown as being split into two separate polygons by an edge-of-road polygon. Single trees having a crown spread less than 10,000 square feet will not be captured.

Land use types (i.e., pasture land, agricultural fields, open fields, etc.) outside of the wooded area will not be separately identified and graphically labeled.

Other cultural features such as cemeteries, athletic fields, golf courses, fences, landfills, retaining walls, swimming pools, sand and gravel sites, storage tanks, smokestacks, and masonry walls will not be captured or separately identified.

This coverage contains the vegetation areas. Features were captured from aerial photography conducted April, 1993. Annotation is defined for two subclasses, TREE and DTREE. Both subclasses are ARC/INFO symbol 2.

Location: L:\PGCO\LAYERS\1993\LIB\<200SHEET>\VEGET
File size: Approximately 74.2KB
Created: ASI
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: ZONING
Theme: PLANIMETRIC & TOPO
Source: MARYLAND NATIONAL CAPITOL PARK & PLANNING COMMISSION
Describe: PROPERTY ZONING AREAS

This coverage represents the zoning of property in Prince George's County as adopted and approved December 1997 by M-NCPPC, Information Permit & Review Division. The zoning covers Residential, Commercial, Industrial, Comprehensive, Planned Community, and Overlay District zones. Their definitions conform with the Department's AGuide to Zoning Categories@ dated November 1997, and all zoning is in compliance with Prince George's County's Zoning Ordinance.

COVERAGE DERIVATION:

The polygons from the Department's most current property base coverage were used to establish the polygon features of the Zoning layer. The polygons were labeled with their respective zoning definitions and then dissolved to remove boundary lines and excess labels between any polygons bearing the same zoning labels. The resulting coverage reflects regions of zoning without parcel boundaries. Other unzoned features were captured as polygons and coded respectively water features as AWATER@, right-of-way and railroads as AROAD@, and land outside the county or not governed by the county as AOUT.@

The Polygon Attribute Table (PAT) of the Zoning layer consists of three attribute items under which polygons may be categorized. The first item AZONING@ represents any one of the major categories of zoning such as AR-55"; whereas the item AZONING1" represents single coincidence zones where two categories of zoning occupy a common geographic area. The third item AZoning2" will cover multiple coincidents where three or more categories of zoning occupy a common geographic area. Zoning categories are coded in the same format as described in the AGuide to Zoning Categories@ dated November 1997, with the exception of AM-U-TC@ which due to set field widths is coded as AMU-TC@. Polygons of the zoning layer have been captured on a sheet to sheet basis. The box which contains the polygons is representative of the bounds of a single sheet.

Annotation has been divided into four subclasses. AANNO.BASE@ consists of standard text, findings and amendments with an annosize of 25, AANNO.BASE1" is standard text with an annosize of 50, whereas AANNO.BASE2" holds standard text with an annosize of 100. Any unusual zoning text or notes are maintained in AANNO.MISC@ and have an annosize of 25. All annotation features are represented using symbol 1.

The Arc Attribute Table (AAT) of the zoning layer includes the item AOVERLAY@ which permits the viewing of the overlay continuous boundary unbroken by right-of-way when arcs with an overlay value of 1 are selected.

The zoning layer's item BND-STATUS in the .aat file holds numerical entries indicating the status of the arcs in the layer. The possible numerical entries run from 0-9. The definitions for those entries are as follows.

0 = Arcs represent true zoning boundaries, to the best of our knowledge at this time.

1 = Arcs predate subdivision of property. Subdivisions results in creation of new zoning parcel splits. The zoning lines in these cases have not been altered, but coded to add clarity to the user's analyses of those questionable boundaries. Plat data may conflict with existing, delineated property boundaries, and may negatively effect zoning. Updates from the assessor's data /taxmaps, result in newly delineated parcels to the property layer. Validity of these boundaries as well as zoning will have to be clarified.

2 = Arcs conflict with unsubdivided property. Review and examination of deeds and assessor data and records is required to resolve those property boundaries and affected zoning boundaries.

3 = Arcs are negatively affected by shifts in the property layer. Parcel data mimicked from taxmaps caused property layer and zoning layer conflict. Property layer data issues such as parcelcodes equal to '?', or blank polygon attributes, do not clarify ownership or r/w issues for zoning. Aerial photography is useful in locating correct property boundaries. In most of these cases the zoning line has been delineated correctly using the mylar, the last official version of zoning, or other available survey data. Erroneous boundaries have been acknowledged by the Property Team and are scheduled to be researched and amended. The arcs have been coded to draw the users attention to the fact that there are underlying, unresolved property layer issues that may hamper their interpretation of the map. Plat and deed data should be researched and used to correct these adjust and fit caused property shifts.

4 = Arcs represent approved SMA boundaries now conflicting with the existing property layer. Cause and origin of conflict must be determined.

5 = Arcs represent approved ZMA boundaries taken from surveys now conflicting with the property layer. Cause and origin of conflict must be determined.

6 = Arcs represent zoning lines affected by shifts of the shoreline. Shifts may, or may not create a zoning conflict. Shift will have to be assessed on a case by case basis to ensure that zoning retains its intended purpose.

7 = Arcs represent zoning that conforms to the MD/Wash Regional District Boundary (MWRD). Some discrepancies in that boundary from the mylar to GIS have been noticed. Due to historical gaps in that layer's data, the MWRD boundary is targeted for additional review and research. The coding of these arcs alerts the user that there are questions concerning these boundaries.

8 = Arcs represent zoning boundaries that originally conformed to stream and creek centerlines versus the new property boundaries that currently exist. Since zoning is usually defined by visible land features, and zoning boundaries had originally been determined using them, then the validity of the newly delineated property boundaries will have to be determined.

9 = Arcs of unknown origin. These arcs are not represented on mylars, plats, taxmaps, special exceptions or ZMA' s as far as we know. We have no knowledge at this time, whether a legitimate action supported the entry of these arcs. These lines are targeted research issues.

Location: L:\PGCO\LAYERS\ZONING\<200SHEET>\ZONING
File size: Approximately 34KB
Created: CENTECH & M-NCPPC/PG/GIS
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: OVERLAY
Theme: PLANIMETRIC & TOPO
Source: MARYLAND NATIONAL CAPITOL PARK & PLANNING COMMISSION
Describe: CRITICAL AREAS, TRANSIT DISTRICT OVERLAY, AND DEVELOPMENT DISTRICT OVERLAY

This coverage represents the boundaries of Critical Areas, Transit District Area Zones, and Development District Zones as approved by the County Council. Critical Areas refer to the conservation of the Chesapeake Bay area, Transit Districts refer to areas around Metro transit lines and Development Districts refer to the zone applied by Council to the ARM town center for the purpose of ensuring compliance with standards set forth for development in that District. In each case the indication is that added restrictions, control and guidelines shall exist in these areas with regard to development for zoning purposes.

The Critical Area boundaries were extracted from the 1:200 scale mylar Critical Area overlay maps, the Transit District overlay boundaries were extracted from the 1:200 scale mylar Transit District overlay maps, and Development District overlay boundary was extracted using arcs from the GIS property layer (2000), and ARM SMA data approved October 24, 2000, as a reference. The coverage reflects the polygon boundaries of Critical Areas identified as Intense Development, Limited Development, and Resource Conservation areas. It also reflects the boundaries of land identified as surrounding Metro transit lines, and the boundary of the ARM town center Development District. All polygons were labeled with their respective identifying codes.

The Polygon Attribute Table (PAT) of the Overlay layer consists of one item AOVERLAY@. Critical Areas and Transit Areas are coded under this item in the same format as appears in the Department's AGuide To Zoning Categories@, dated November 1997. Critical areas are coded AI-D-O@, AL-D-O@ and AR-C-O@ representing Intense Development Overlay, Limited Development Overlay and Resource Conservation Overlay, respectively. Metro transit line areas are coded as AT-D-O@ representing Transit District Overlay, and the ARM Town Center Development District was coded "D-D-O" representing Development District Overlay. Overlay boundaries were captured on a sheet to sheet basis with a box that defines the bounds of each sheet.

Annotation is covered under the subclasses AANNO.CRITICAL@, AANNO.TRANSIT@ and "ANNO.DEVELOP which each consist of standard text with annosizes of 100, 50, and 25. All annotation features are represented using symbol 1. The Arc Attribute Table (AAT) of the zoning layer includes the item AOVERLAY@ which permits the viewing of the overlay's continuous boundary unbroken by right-of-way when arcs with an overlay value of 1 are selected.

Location: L:\PGCO\LAYERS\ZONING\<200SHEET>\OVERLAY
File size: Random
Created: CENTECH & M-NCPPC/PG/GIS
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

0 = arcs that do not split a primary zone, including those that bound right of ways, but not those that cross right of ways.
1 = arcs that split a primary zone or cross a right of way, but not those that bound right of ways.

Cover: SPECIAL
Theme: PLANIMETRIC & TOPO
Source: MARYLAND NATIONAL CAPITOL PARK & PLANNING COMMISSION
Describe: SPECIAL EXCEPTION PROPERTIES

Represents the boundaries of properties approved for special uses by the District Council. The numbers associated with those boundaries represent the actual applications that were presented for approval. Boundaries and identifying numbers have been deemed to be accurate as of December 1997 by M-NCPPC, Information Permit & Review Division.

These boundaries were extracted from the 1:200 scale zoning mylar overlay maps. Polygons were labeled with their respective special exception numbers. The coverage reflects the polygon boundaries of properties deemed to be special exceptions with their identifying application numbers.

The Special layer has been found to contain as many as four different application numbers within a common geographic area. Therefore, the Polygon Attribute Table (PAT) of this layer has been set up to accommodate up to five different special exception numbers in a single geographic area. The items that allow for entry of more than one number are ASPECIAL1@, ASPECIAL2", ASPECIAL3", ASPECIAL4", and ASPECIAL5". As additional special exceptions are encountered within a common area the new numbers may be calculated to the next vacant item (eg. ASPECIAL2", ASPECIAL3", etc.). Special exception numbers are coded in the same format as they appear on the actual applications, eg. ASE-4032" or ASE-706", etc. Special exception polygons are captured on a sheet to sheet basis, however, there is no box that defines the bounds of each sheet.

Annotation is covered under one subclass called AANNO.SPECIAL@ which consists of standard special exception text with an annosize of 20. All annotation features are represented using symbol 1.

Location: L:\PGCO\LAYERS\ZONING\<200SHEET>\SPECIAL
File size:VARIES ACCORDING TO TILE VIEWED
Created: CENTECH & M-NCPPC/PG/GIS
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Cover: PROPERTY
Theme: PLANIMETRIC & TOPO
Source: MARYLAND NATIONAL CAPITAL PARK & PLANNING COMMISSION
Describe: PRINCE GEORGE'S COUNTY

This coverage was created in 1993 from the original 1:2,400 scale M-NCPPC property base mylars and covers all of Prince George's County. Today the property boundaries are maintained in ESRI Spatial Database Engine (SDE)

Location: L:\PGCO\LAYERS\PROPERTY\PROPERTY.SHP
File size: Approximately 84 MB
Created by: ASI and CENTECH
Maintained by: M-NCPPC
Contact: GIS Staff (301) 952-4779
Data format: Available in ESRI SDE & Shapefile Format
Data structure:

Because each parcel can have more than one owner, this layer requires two additional data
tables in order to extract tax assessment information. The two tables are the cross reference
table (XREF) and the State of Maryland Tax Assessment table (LDF).

The XREF table is only used to connect the property shape table to the LDF table. Below is a detailed
description of the LDF table.

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
Property_i	2	2	N	0	-
Elec_dist	2	2	C	-	-
Account	7	7	C	-	-
Acreage	13	13	N	4	-
Lot	5	5	C	-	-
Block	4	4	C	-	-
Section	2	2	C	-	-
Parcel	3	3	C	-	-
Property_d	72	72	C	-	-
Plat	8	8	C	-	-
Planarea	3	3	C	-	-
Paz	4	4	C	-	-
Mapgrid	5	5	C	-	-
Map200	7	7	C	-	-
Flood_pla	1	1	C	-	-
Sewer_serv	1	1	C	-	-
Census_tra	6	6	C	-	-
Census_blo	4	4	C	-	-
M-NCPPC_use	3	3	C	-	-
Town_code	2	2	C	-	-
Zone	4	4	C	-	-
Exempt_cla	3	3	C	-	-
Exempt_sta	1	1	C	-	-
Sub_name	72	72	C	-	-
Sub_code	6	6	C	-	-
Liber	5	5	C	-	-
Folio	3	3	C	-	-
Transfer_d	8	8	C	-	-
Year_built	4	4	C	-	-
Struc_code	10	10	C	-	-
Struc_sqft	7	7	I	-	-
Azc	3	3	C	-	-
Residentia	1	1	C	-	-
Sales_pr	9	9	I	-	-
Sales_pr_i	2	2	C	-	-
Curr_asses	10	10	C	-	-
Pref_asses	10	10	I	-	-
Pref_code	6	6	C	-	-
Fcv_land	10	10	I	-	-
Fcv_imps	10	10	I	-	-
Owner_name	36	36	C	-	-
Mail_stree	45	45	C	-	-
Mail_city	30	30	C	-	-
Mail_state	2	2	C	-	-
Mail_zip5	5	5	C	-	-
Mail_zip4	4	4	C	-	-
Ico_name	36	36	C	-	-
Mail_ind	1	1	C	-	-
House_num	6	6	C	-	-
House_suff	1	1	C	-	-
Street_nam	28	28	C	-	-
Street_typ	4	4	C	-	-
Street_dir	2	2	C	-	-
Unit	5	5	C	-	-
City	28	28	C	-	-
Zip5	5	5	C	-	-
Zip4	4	4	C	-	-
Objectid	10	10	I	-	-
Conflicts	1	1	C	-	-

Property_i - Election District & Tax Account Number

Elec_dist - Assessment District Number

Account - Tax Account Number

Acreage - Total Acreage for that particular tax account number

Lot - A division of a block

Block - A division of a section

Section - A division of a plat

Parcel - A designation given to a property not located within a subdivision/plat

Property_d - Part of the legal description of the property that is not elsewhere contained in individual fields

Plat - Subdivision plat number that is assigned by the County at the time of recordation

Planarea - A legally described area, defined by the Zoning Ordinance, and bound by physical features. Used to define community interest.

Paz - Policy Analysis Zone. Developed by COG for projection of population and employment.

Mapgrid - Combination of columns TAXMAP and GRID

Map200 - WSSC grid sheet number

Flood_pla - 100 year flood plain

Sewer_serv - A code used to describe the status of water and sewer service on the property. Valid values 1 - 6.

Census_tra - Census Tract number - Defined by the Census Bureau for reporting census data.

Census_blo - Census Block number - Defined by the Census Bureau for reporting census data.

Mncppc_use - Value given that categorizes the use of the property.

Town_code - Value 72-99 if property is in one of the incorporated towns. Blank if not in an incorporated area.

Zone - The zoning on the property determined from the M-NCPPC adopted zoning map.

Exempt_cla - Assessor’s code to describe an exempt or partially exempt account.

Exempt_sta - A statewide code that describes the taxability of the property.
Valid values are: 0 (county and state taxable), 1 (state tax, county exempt), 2 (state exempt, county tax),
3 (county and state exempt).

Sub_name - A name associated with the SUB_CODE, assigned by the Assessor. Not the M-NCPPC name associated with the plat number

Sub_code - An arbitrarily generated assigned number to distinguish a portion of a plat or a combination of plats. Assigned by the Assessor.

Liber - Designation of the book in which the recorded deed information for the property is located.

Folio - The page number of the book in which the recorded deed information for the property is located.

Transfer_d - The date the property transferred ownership.

Year_built - The year the improvement on the property was built. Not the same as the construction date.

Struc_code - Describes some of the physical attributes of the improvement on the property (# of stories, type of exterior, etc.).

Struc_sqft - The total sq. ft. of the structure.

Azc - A.K.A. PG USE CODE. A use code assigned by the Assessor’s Office.
Valid values: 001, 002, 003, 004, 005, 007, 011, 061, 065, 067, 901, 902, 903, 904, 905, 907, 911, 912, 961, 965, 967. Use codes beginning with 9 designate an account as totally exempt from all levies (but subject to charges).

Residential - H if property is owner occupied, N if property is not owner occupied, D if property is dual use (part residence, part business).

Sales_pr - The selling price of the property at the time of transfer. $0 (zero) is valid.

Sales_pr_i - Type of sale. TS (True Sale), IO (Interest Only), MA (Multiple Accounts), NC (No Cost), UN (UNknown).

Cur_asses - The assessment on an account calculated: ((FCV_LAND + FCV_IMPS) * 40%) where 40% is the growth factor.

Pref_asses - The assessment on preferential accounts calculated by: ((full cash value of the land * 50%) +
(full cash value of the improvement * 40%)) where 40% is the growth factor.

Pref_code - Identifies the type of property receiving a preferential assessment (but only) when combined with a PG Use Code of 003 or 903. First digit of 1 = country club, 2 = planned development, 3 = farm, 4 = marshland, 5 = woodland, 6 = DNR contract.

Fcv_land - The value of the land portion of the property (aka: market value of land).

Fcv_imps - The value of the existing improvement(s) the property (aka: market value of improvements).

Owner_name - The name of the current owner as it appears on the recorded deed.

Mail_stree - house number, street name or route number, p.o. box number, etc., to which mail is delivered.

Mail_city - The city to which mail is delivered.

Mail_state - The state or territory to which mail is delivered.

Mail_zip5 - The zip or postal code to which mail is delivered .

Mail_zip4 - The zip or postal code to which mail is delivered (2nd 4 digits).

Ico_name - The name of the in care of addressee.

Mail_ind - ‘O’ if mail address is an owner address, ‘I’ if mail address is an in care of address.

House_numb - The house number, as assigned by M-NCPPC.

House_suff - The suffix, if any, associated with the house number.

Street_nam - The name of the street on which the property is located.

Street_typ - The street type or US Postal Service approved abbreviation of the street type.

Street_dir - The general direction of the street relative to the city or town in which it is located.

Unit - The unit number, if any, of the premise, such as might exist in an apartment building.

City - The city, town, or municipality associated with the premise Zip Code.

Zip5 - The Zip Code of the premise.

Zip4 - The Zip Code+4 of the premise.

Objectid -

Conflict -

Cover: 65IMAGE
Theme: THEMATIC
Source: M-NCPPC Staff
Describe: 1965 AERIAL PHOTOGRAPH INDEX COVERAGE
Location: L:\PGCO\LAYERS\COUNTY\65IMAGE
File size: 150KB
Created: M-NCPPC
Contact: GIS STAFF (301) 952-4779
Data format: ARC/INFO COVERAGE 8.x FORMAT
Data structure:

Point Attribute Table (PAT)

Arc: items 65image.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
FLGTPATH	2	2	N	0	-
PHOTONUM	2	2	C	-	-
PHOTO	50	50	C	-	-

FLGTPATH - Horizontal number used to represent the photograph.

PHOTONUM - Vertical number used to represent the photograph.

PHOTO - Location of the image.

Cover: 72IMAGE
Theme: THEMATIC
Source: M-NCPPC Staff
Describe: 1972 Aerial Photograph Index Coverage.
Location: L:\PGCO\LAYERS\COUNTY\72IMAGE
File size: 150KB
Created: M-NCPPC
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Point Attribute Table (PAT)

Arc: items 72image.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
FLGTPATH	2	2	N	0	-
PHOTONUM	2	2	C	-	-
PHOTO	5	5	C	-	-

FLGTPATH - Horizontal number used to represent the photograph.

PHOTONUM - Vertical number used to represent the photograph.

PHOTO - Location of the image.

Cover: 98IMAGE1, 98IMAGE3, 98IMAGE12
Theme: THEMATIC
Source: VARGIS
Describe: 1998 AERIAL PHOTOGRAPH INDEX COVERAGES

These coverages contain the grid system for the 1998 Aerial Photographs as defined by VARGIS for delivery to M-NCPPC. Data was imported from Shape Files from VARGIS and corrected where needed during delivery of digital photographs. The 98image1 is for all 1 foot resolution photography, the 98image3 is for all 3 foot resolution photography, and the 98image12 coverage is for all of the 12 foot, 24 foot, and 40 foot resolution photography. Attributes are limited to the name of the image. (Without the .tif extension)

Location: L:\PGCO\LAYERS\COUNTY\98IMAGE1, or 98IMAGE3, or 98IMAGE12
File size: 297KB
Created: M-NCPPC, Research Section
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format

Polygon Attribute Table (PAT)

Arc: items 98image*.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
IMAGE	16	16	C	-	-

IMAGE - Name of image without .tif extension.

Cover: AFAMCOMM
Theme: THEMATIC
Source: M-NCPPC Historic Preservation Section
Describe: The coverage was developed using a 1:2400 property base, the county boundary and major roads as a reference. The primary sources of information used were boundary maps of the historic communities located in the historic preservation files and references to the stream layer when applicable. The attributes include the PG-ID, the community name and community classification. Additional information is documented in the Historic Sites and Districts Plan published by Prince George’s County Planning Department.
Location: L:\PGCO\LAYERS\COUNTY\AFAMCOMM
File size: 41KB
Created: M-NCPPC Historic Preservation Section
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format

Polygon Attribute Table (PAT)

Arc: items afamcomm.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
PGID	16	16	C	-	-
CLASS	50	50	C	-	-
NAME	100	100	C	-	-

PGID - Prince George's County historic identification number.

CLASS - Community classification.

NAME - Community name.

Cover: AFAMHIST
Theme: THEMATIC
Source: M-NCPPC Historic Preservation Section
Describe: The coverage shows the location of designated historic sites, resources and documented properties that are historically African-American. The information is suitable for presentation at a scale of 1:2400. COVERAGE DERIVATION The coverage was developed using the historic point, county boundary and the roads layers. The primary source of information came from the 1996 Prince George’s County African-American Heritage Survey. The attributes associated wit this coverage includes the resource name, PGID, classification and type. Additional data about these sites are available in a related file based on the identifying PGID number and are documented in the Prince George’s County Planning Department Historic Sites and District Plan.
Location: L:\PGCO\LAYERS\COUNTY\AFAMHIST
File size: 52KB
Created: M-NCPPC Historic Preservation Section
Contact: GIS Staff (301) 952-4779
Data format: Arc/Info Coverage 8.x Format

Point Attribute Table (PAT)

Arc: items afamhist.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
NAME	100	100	C	-	-
PGID	10	10	C	-	-
CLASS	50	50	C	-	-
TYPE	8	19	F	11	-
ANGLE	8	9	F	-	-
LABEL_ID	10	10	C	-	-

NAME - Community name.

PGID - Prince George's County Identification number.

CLASS - Community classification.

TYPE - Community type.

ANGLE - .

LABEL_ID - Unique mapping ID.

Cover: AICUZ
Theme: NOISE IMPACT ZONES
Source: AICUZ STUDY
Describe: NOISE IMPACT ZONES FOR ANDREW'S AIR FORCE BASE

This was created based on the digitized noise contours as found in the 1998 Air Installation Compatible Use Zone (AICUZ) Study for Andrews Air Force Base. The associated attributes were then entered. The various zones are used to identify the noise impacts that would be associated with development proposed in the vicinity of Andrews Air Force Base.

Location: L:\PGCO\LAYERS\COUNTY\AICUZNOISE
File size: Approximately 14.2 KB
Created: M-NCPPC ENVIRONMENTAL PLANNING SECTION
Contact: J. MARKOVICH (301) 952-5403
Data format: Arc/Info Coverage 8.x Format
Data structure:

Polygon Attribute Table (PAT)

Arc: items acuiznoise.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
NOISE	4	4	I	-	-

NOISE
65 = Zone with noise levels of 65 to 70 dBA
70 = Zone with noise levels of 70 to 75 dBA
75 = Zone with noise levels of 75 to 80 dBA
80 = Zone with noise levels of 80 to 85 dBA
85 = Zone with noise levels in excess of 85 dBA

Cover: AIRPORT
Theme: Airports of Prince George's County
Source: Yellow Pages
Describe: This layer contains the location of all airports in Prince George's County, Maryland.
Location: L:\PGCO\LAYERS\COUNTY\AIRPPORT
File size: Approximately 7 KB
Created: M-NCPPC GIS Section
Contact: (301) 952-4779
Data format: Arc/Info Coverage 8.x Format
Data structure:

Point Attribute Table (PAT)

Arc: items airport.pat

ITEM NAME	WIDTH	OUTPUT	TYPE	N.DEC	ALTERNATE NAME
NAME	50	50	C	-	-
ADDRESS	50	50	C	-	-
CITY	20	20	C	-	-

Cover: APA
Theme: AVIATION POLICY AREAS
Source: CB-51-2002
Describe: AVIATION POLICY AREAS
The Aviation Policy Areas are intended to establish a standard of safety and compatibility for the occupants of land in the Prince George's County. These standards benefi