DOQQ

Digital Orthographic Quarter- Quads (DOQQs) are aerial photographs that have been corrected to remove any distortion. Doing this allows the photos to be used as flat maps with more accurate measurement.

This DOQQ example is of Sabine Pass, Texas. It contains enlargement to show one meter resolution.

http://www.whitestar.com/orthoquads.html

DEM

Digital Elevation Maps (DEMs) show terrain topographyin Raster format.
This DEM example shows the elvations of areas within North America.

http://eros.usgs.gov/products/elevation/gtopo30/hydro/na_dem_img.html

DLG

A DLG (Digital Line Graph) maps show boundaries, roads, and other various information found on topographical maps. DLGs are a form of graphic information system.

This is a DLG of Columbus, Georgia. It contains roads (red lines), trails (black lines) and olympic venues (green area).

http://ga.water.usgs.gov/olympics/columbus.html

DRG

A digital raster graphic (DRG) is a type of U.S. Geological Survey. It is a form of digital map.
This one is of Evergreen Lake and Golf Course.
http://www.mapmart.com/Products/TopographicalMaps/SeamlessDRG.aspx

Isopleth

An Isopleth map shows a feature by connecting lines of equal value.
In this example, the area around three municipal waste incinerators in Jacksonville was examined. The extent of a toxic chemical average (100 micrograms per meter) was noted by the isopleth line.
http://www.stonelions.com/Jacksonville.htm

Isopach

An Isopach map consists of lines connecting places of equal value (thickness) for a given theme such as rainfall or temperature.
This map shows the thickness in feet of shale deposition along the Appalachian Basin. The purple area is a thinner area and the red is the thickest.
http://www.searchanddiscovery.net/documents/2007/07022lash/index.htm

Isohyets

Isohyet maps are used in recording amounts of precipitation during a specific period.
This isohyet map was used to show average rainfall in milimeters. The information provided will help farmers choose which clover to grow based on his/her location on the map.
http://www.dpi.nsw.gov.au/agriculture/field/pastures-_and_-rangelands/establishment/clover/part-f---choosing-the-right-sub-clover-v