The Topo Maps layer is based on Pennsylvania DRG data. A Digital Raster Graphic (DRG) is a raster image of a scanned USGS topographic or planimetric map.

All the drg's that cover Pennsylvania were projected from UTM to Albers NAD 83. The projected rasters were then combined into a single statewide ArcSDE raster mosaic stored in Sql Server. This raster layer is then displayed in SoilMap. The collar area of the DRG was removed prior to the mosaicing process. A single color map was applied to all the data.

For More Information - Visit the USGS Digital Raster Graphics page.
To download DRG data for Pennsylvania, visit PASDA.

Note: All SoilMap source data has been projected to an Albers Conical Equal Area projection with the following parameters.

PROJCS["Albers Conical Equal Area",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Albers"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-78.0],PARAMETER["Standard_Parallel_1",40.0],PARAMETER["Standard_Parallel_2",42.0],PARAMETER["Latitude_Of_Origin",39.0],UNIT["Meter",1.0]]

The data and documentation on SoilMap are provided 'as is' and the User assumes the entire risk as to their quality and performance. SoilMap source data was produced at a variety of scales and may not be suitable for use at larger scales.