Post 27: Digital Ortho Quarter Quad (DOQQ)

The example shown above is a DOQQ, and is one of the better ones I could find without an overlay . . . which probably isn't saying much. As you can see, it is a raster-based image that has been compressed to become a 2D map. In other words, it is a combination of a picture of an area and a map of the same area. The one shown is off of a software website, and the original users did not bother to mark it. It is actually 17 overlain DOQQs.

Where example was found: http://www.goldensoftware.com/products/didger/didgernew.shtml

Post 26: Digital Elevation Model (DEM)

As following with the pattern of the previous posts, this is a digital representation of a land surface. It is also know as Digital Terrain Model (DTM), and are usually created through remote sensing techniques. The example shown above is a 7.5 minute image of Sturgis, South Dakota.

Where example was found: http://eros.usgs.gov/products/elevation/dem.php

Post 25: Digital Line Graph (DLG)

Unlike the previous example, this is a translated version of a USGS map. Digital vector representations of cartographic data is used in this example. This is also used in GIS systems and the like

Where example was found: http://www.dnr.sc.gov/GIS/descdlg.html

Post 24: Digital Raster Graphics (DRG)

A DRG is actually an image that has been copied from a map from the US Geological Survey. In short, you take a topographic map from them, scan it, and print it. This is used in many GIS or other computer programs. The map shown is of an area by the Colorado River.

Where example was found: http://www.tceq.state.tx.us/gis/drg.html

Post 23: Isopleths

Isopleths show data in the third dimension, rather than the second. This can be a variety of data types, including height and depth, as well as more insubstantial data. The example shown is an isopleth of an area in California.

Where example was found: http://www.envisci.ucr.edu/ensc176/es176_2003/ENSC_176_Summer_2003.html

Post 22: Isopach

While previous contour maps have been used to display distance or weather factors, this type is used to show the thickness of rocks and/or geographic formations in an area. This would be useful to geologists. The example found is of a sediment isopach around an offshore coal oil deposit in the Helocene overburden.

Where example was found: http://seeps.geol.ucsb.edu/pages/isopach.html

Post 21: Isohyets

A isohyet is a contour map that uses its lines to represent the amount of rainfall in an area. This is useful in mapping out good farm land. The image shown above is a map of an area in New Zealand, and is, of course, an example of an isohyet contour map.

Where example was found: http://img2.scoop.co.nz/stories/images/0808/3d0ea09ab5cbfe1ff03f.jpeg