Range graded proportional circle map

A proportional circle map is a statistical map that shows its information by using circles that are proportional to the information that is being provided. In a range graded proportional circle map, only a set number of circles are used to convey the information that is provided. This picture tries to represent what the population in the region might look like in the “real world.”

Continuously variable proportional circle map

A proportional circle map is a statistical map that shows its information by using circles that are proportional to the information that is being provided. The circles come in this continuously variable proportional circle map shows circles of different sizes which represent the distribution of the variable.This particular picture is of England and is dealing with the major industries in the country and the circles are proportional to the variable being measured.

DOQQ

DOQQs or digital orthophoto quarter quads are digital images produced by the USGS. They contain orthorectified aerial photography at a resolution of 1 meter. The uniform scale of a DOQQ makes it possible to determine map measurements or to overlay information, using the digital orthophoto as a base map. Features are represented in their true ground position, making direct measurement of distance, areas, angles, and positions possible. This picture is a DOQQ of Lake Travis in Austin, Texas.

DEM

DEM stands for a digital elevation model which is a digital representation of ground surface topography or terrain. DEMs are commonly built using remote sensing techniques, however, they may also be built from land surveying. DEMs are used often in geographic information systems, and are the most common basis for digitally produced relief maps. This particular picture is of a DEM for Honolulu, Hawaii.

DRG

DRG stands for a digital raster graphic which 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 picture is a DRG of Illinois.

Isopleth

An isopleth is a line drawn on a map through all points of equal value of some measurable quantity. In many meteorologic, oceanographic, or geologic studies some physical or chemical property is examined that varies from place to place on a map. Isopleths showing the quantity of the property being studied can be drawn on the map to highlight regional trends of high or low abundance of that property. This particular picture shows hydrogen ion concentration as pH from measurements made at the field laboratories in 2003.

Isobars

A line drawn on a weather map connecting points of equal pressure is called an isobar. The isobars are generated from mean sea level pressure reports and the pressure values are given in millibars. This picture shows closed isobars around a low pressure cell.