DLG

Topographic maps of the USGS are well known to hikers and others. The USGS has digitized many of these maps and published them on the Web as Digital Line Graph (DLG) files in vector form. This particular DLG is of the San Francisco North Quadrangle.

http://www.cs.arizona.edu/icon/oddsends/dlgvu/sfnorth.gif

DRG

A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) standard series topographic map, including all map collar information. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator projection. This DRG is a map of a section of Michigan.

http://lter.kbs.msu.edu/maps/GIS/DRG_d.jpg

Isopleths

An isopleth map simplifies data that is continuously distributed. It shows the data being displayed as a third dimension on the map. This map measure acid rainfall in the United States by looking at the pH level of rain in different areas.

http://dwb4.unl.edu/Chem/CHEM869V/CHEM869VLinks/weather.about.com/newsissues/weather/library/weekly/aa071600a.htm

Isopach

An isopach map connects points of equal thickness in a given area. Isopach maps are used in structural geology, sedimentology, and volcanology. This map in particular shows the distribution of barnett shale in the western United States.

http://www.republicenergy.com/Articles/Barnett_Shale/Isopach_Barnett_Shale.jpg

Isohyets

An isohyet is a line joining points of equal precipitation on a map. A map with isohyets is called an isohyetal map. This is a isohyet map of Borneo.

http://www.forest.sabah.gov.my/caims/Climatic%20information/Stations/Maps/Isohyet/isohyet.gif

Isotachs

An isotach is a line on a weather map or chart connecting points where equal wind velocities have been recorded. This map is of the Foothills and is an excellent depiction of isotachs.

http://www4.ncsu.edu/~nwsfo/storage/cases/20030123/small.eta_12z_300_000hr.gif

Isobars

Isobars are lines of equal pressure, and joins points which share that share values. This isobar map in particular, shows sea level pressure for a given study area for the UK and Ireland.

http://www.weatheronline.co.nz/reports/wxfacts/isobars1.gif