DRG

DRG's are scanned images of a USGS standard series topographic map. The raster includes the original border information.

DLG

DLG's contain a lot of information, from topography, hydrography, boundaries, roads, utility lines, and more. Data about map features are stored as arcs and polygons.

DEM

A DEM is a digital file that includes terrain elevations for ground positions at regularly spaced horizontal intervals. DEM's may be three-dimensional images (above) or colorized to bring out relief. Data is recorded, stored, and processed in a pixel. This process is the raster format.

DOQQ

A DOQQ is an aerial photo that has been georeferenced and orthorectified. Orthorectification removes distortion from the aerial phots so that it may be used as a flat map.

Classed Choropleth maps

Classed choropleth maps often combine data into a smaller number of groups and portray it in an interval system. The map above shows methane emissions in tons in North Carolina. Because the number of groups used is low, very little information is conveyed. The pattern of colors is often difficult for readers to follow.

Choropleth Maps

This choropleth map shows the percentage of people who are Hispanic in Florida, by county. Another way choropleth maps areally average data is by density. Choropleth maps convey very little information. In this case, only the percentage of Hispanics in Florida is shown.

Cadastral Map

Cadastral maps are used to show parcels of land and ownership. I was a realtor for quite some time and we used cadastral maps often. Quite often referred to as a "plat map," cadastral maps are handy when trying to decipher land boundaries and easements.

PLSS Maps

PLSS system is first set up by establishing starting points for each region. Principal meridians and baselines extend from the starting points. The entire system uses 34 principle meridians and baselines. Most of the U.S. is covered by the PLSS. Areas not covered are considered unsystematic.