| Description | Spatial | Attributes |
Spot elevations for Prince George's County, Maryland
This coverage contains ground and water spot elevations. Annotation is defined for three subclasses, gnd_spot, non_cip_spot and wat_spot. 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. This layer was created by ASI Inc.