Population Profile

A Population Profile, or Population Pyramid, shows sex and age distributions for a determined area, such as a country or region, at a specific period of time. These graphs are useful in understanding the demographic transition of a geographical area. Thin patterns show low fertility, thick patterns show high fertility. A thin column with a bulbous top shows below replacement level fertility. A significant imbalance between the two sides which indicate sex of population may indicate war, in which there is a reduction of men, or infanticide of girls in places like China where there is strict population control along with a desire for male offspring. The pyramid above is for Ethiopia in 2005. The rapidly diminishing pyramid indicates both a high fertility and mortality rate for this country.

Scatterplot

A Scatterplot uses Cartesian coordinates to graph two variables for a data set. The data is graphed using points, the independent variable plotted along the horizontal axis and the dependent variable along the vertical axis. This kind of visualization is useful for examining correlations. When both variables increase, there is a positive relationship and when one increases and the other decreases, there is a negative one. A line is sometimes included on a scatterplot to indicate the trend of the data, a close fit between this trend line and the points indicates a correlation. This scatterplot plots the FIFA ranking of national soccer teams against their respective countries GNP per capita.

Index Value Plot

An Index Value Plot is a geovisualization that plots an index value rather than an absolute number. An index value is determined and then the values for subsequent periods are divided by the initial average and multiplied by 100, so that all of the plots values are relative to the index value. A common index used in economics is the market basket known as the basket of consumer goods, used to define the Consumer Price Index. The accompanying index value plot indexes home values using a benchmark value from 1890 and factoring out inflation. It shows the high of the housing value boom in the early years of the 21st century.

Accululated Line Graph (Lorenz Curve)

An Accumulated Line Graph or Lorenz Curve is a type of geovisualization that graphically represents cumulative distribution. It is frequently used in economics to show inequality in wealth or size. It is made by plotting the cumulative distribution of the variable against the cumulative frequency distribution of the individuals that possess the variable. This Accumulation plot is the Lorenz curve for Household Income and Expenditures in the years 2002-2003 for the Maldives, an island nation in the Indian Ocean.

Bilateral Graph

Graphs can be Bilateral, based upon two data series, in order to compare two related variables. Bilateral Graphs can be of varying types, including bar and line. Often in bilateral bar graphs one data series is measured up or to the right, while the other is measured downwards or to the left. Bilateral graphs can show negative and are frequently used to represent how an increase in one data series cause either a decline in another or an accompanying rise. The bilateral line graph above shows the relationship between gas prices and consumer spending in the US for most of 2007.

Nominal Area Choropleth

Nominal Area Choropleth maps use a qualitative classification which has no implicit ordering to represent data by category. This nominal area choropleth uses colors to represent qualitatively the geologic periods of the US.

Unstandardized Choropleth Map

Unstandardized Choropleths portray areal data without averaging within specified units. The data is presented as a total value. The map above is shows total water use per day by state in the US.

Standardized Choropleth Map

A Standardized Choropleth map is on that has been areally averaged, that is one in which the numerical data has been standardized to a specific unit, such as population per square mile or percentage per a unit of area. Standardized Choropleths are useful because the allow units to be compared more effectively. Using large units may be misleading because there may be variables within the area of the unit. The Choropleth map to the left shows population per square mile in the Appalachians.

Remote Sensing

EAARL DEM Image overlay of the Dry Tortugas National Park showing submerged topography using lidar. NASA's Experimental Advanced Airborne Research Lidar (EAARL) is a raster-scanning green-wavelength water-penetrating lidar. The images are normally taken from a Cessna aircraft using digital multi-spectral color infrared cameras.

http://coastal.er.usgs.gov/remote-sensing/advancedmethods/googleearth.html

Bivariate Choropleth Map

Bivariate Choropleth Maps uses two variables to show the distribution of two sets of data on one map, using two colors or sets of cartographic symbols. These maps are used to analyze or communicate correlations between data. This map combines the variables for Life Expectancy and GNP Per Capita for the African continent in 1989.

Univariate Choropleth Map

Univariate Choropleth Maps are simple choropleth maps which deal with one subject or data set. The accompanying map uses one variable, that of the percentage of Americans living in poverty, by county in 2000, as its basis. Data are classified by a natural breaks algorithm.

Unclassed Choropleth Map

In an Unclassed Choropleth map there are as many intervals as there are areal units. This map uses a continuous grayscale to represent the proportion of children ages 0-15.

Classed Choropleth Map

A Classed Choropleth Map is a thematic map that uses color or shading to represent statistical information and areal data. The boundaries are defined and the data often is areally averaged. Classed Choropleth maps combine the data into ranges and the data is shown in intervals, using classification techniques such as equal steps, quantiles, natural breaks, and minimum variance. This Classed Choropleth map uses seven ranges to classification levels to communicate population density of New England in 2000.

Range-Graded Proportional Circle Map

A range graded proportional circle map is a proportional circle map which scales the circles to ranges of data. The data are divided into groups using classifications such as equal breaks, quantiles, natural breaks, and minimum variance. The circles are of a set size corresponding to each of the ranges. The map above uses range-graded circle to show number of internet uses in Europe in 2004.

Continuously Variable Proportional Circle Map

A continuously variable proportional circle map is a proportional circle map, which is one that uses circles to map point data, which scales the circles to the individual data. The circles can be of any size since they correlate to the data. The accompanying map uses continuously variable proportional circles to show the major industries of West Germany.

DOQQs

DOQQ stands for Digital Orthophoto Quarter Quadrangle and is a computer generated image derived from an aerial photograph that has been manipulated to remove image displacement caused by the relief of the terrain and the position of the camera. The USGS makes both grayscale and color-infrared DOQQs covering a quarter of a 7.5 minute quad or approximately four miles across the top by just over four and a half miles on the side. This infrared DOQQ was made of the lower Colorado River near Lago Vista TX as part of a flood study.

DEM

DEMs (Digital Elevation Models) data) are digital representations of geographic information that are in raster format and are made up of arrays of regularly spaced elevation values which are referenced horizontally to a geographic coordinate system. The USGS makes maps using five types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM. The USGS collects DEM data by interpolation from vectors or digital line graph (DLG) hypsographic and hydrographic data. This image is an X-band DEM of Oetztal, Austria, located in the Central Alps at the border between Switzerland, Italy, and Austria. It was acquired by imaging radar aboard the space shuttle Endeavour in 1994. The Gepatschferner glacier seen at the left of the image center is in light blue.

DLG

DLG (Digital Line Graph) files are digital vector representations used by the US Geological Survey. Data files are made from aerial photos or other maps which are then digitized. DLGs are made available in a variety of scales, 1:24,000 and 1:100,000 are the most common. This DLG is of Beaufort, SC and shows hydrography and roads.

Isopachs

An Isopach is an isoline or contour that connects equal points of thickness of a geological stratum formation, such as rock. The accompanying map uses isopachs to describe the thickness of ashfall from the Cerro Negro volcano in Nicaragua in 1995. Isopachs within the 5.0 cm limit are at 10-cm intervals, and up to 50 cm closest to the crater. For comparison the 2-5 June isopachs are shown.

DRG

DRG (digital raster graphic) is a digitally scanned image of a U.S. Geological Survey (USGS) standard series topographic map. They normally include the original border information, or "map collar." The image is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator (UTM) projection. DRGs are commonly used in GIS applications. This DRG shows Depoe Bay Port and Harbor in Lincoln County, OR.

Isopleths

Isopleths are contour lines or isolines that connect points of equal value on meteorological maps. Isobars, isohyets, isotachs are examples of isopleths. This map is part of a study on how climate affects Salmon survival in the Pacific Northwest, and uses Isopleths to show coastal wind velocity averaged over years 1946-1994.

Isohyets

An Isohyet is an isoline that is used on weather maps to connect points that receive equal rainfall. This map uses Isohyets to show the total rainfall from Hurricane Camille in Nelson County, Virginia for the days of August 19 and 20, 1969. Rainfall measurements are in inches.

Isotachs

Isotachs are a form of Isoline in which connect lines of equal or constant wind speed, used on weather maps. The example shows Isotachs measuring wind speed using knots over the Southeastern US.

Isobars

An Isobar is an Isoline used on a synoptic chart or weather map which connects points of equal pressure. They are generated from mean sea level pressure reports and given in millibars. They are normally drawn at intervals of 2-4 millibars. Curved isobars around an area of low pressure signify a depression, while curved isobars around an area of high pressure describe an anticyclone. This weather map uses Isobars to show areas of equal pressure during Hurricane Wilma over the state of Florida in October 2005.

LIDAR

LIDAR is an acronym of Light Detection and Ranging, and is a remote sensing technology that uses lasers to determine distance and other information. The main distinction between LIDAR and radar is the use of shorter wavelengths, which are good for imaging objects that do not have significant reflectivity, such as smoke, cloud particles and aerosols, making it especially useful for meteorologists. The USGS and NASA teamed up to use LIDAR to measure volcano deformation, and the accompanying image shows elevation differences in the crater of Mount St. Helens between September 2003 and October 4, 2004 using two airborne LIDAR surveys.

Doppler Radar

Doppler radar uses the doppler effect to measure radial velocity and are used in weather tracking, among other uses such as air defense and traffic control. Weather radars measure both intensity and velocity of precipitation using Pulse-Doppler radar. The image is of Tropical Storm Alberto as it made landfall along the Florida coast Taylor County at around 12:30 PM Tuesday, June 13 2006, about 50 miles southeast of Tallahassee, and is a Doppler radar base reflectivity image from the KTLH Doppler radar.

Black and White Aerial Photography

Black and white aerial photography is a type of remotely sensed imagery that allows for the mapping of landscape and ground cover via photography taken from aircraft and satellites. Changes to surface features such as vegetation can also be tracked via aerial photography. The USGS used aerial photographs to photograph the 50 States and most were taken with black-and-white film. The example above was taken by the USGS as part of the National Aerial Photography Program in August 1993 of the Golden Gate Bridge in San Francisco.

Infrared Aerial Photograph

Infrared Aerial Photography uses color-infrared film to capture geographical images from a camera mounted on high-altitude aircraft or satellites. Near-infrared light is invisible to the human eye but when added to a photograph it enhances the image. The result is "color-infrared" photography. Certain geographic features, such as vegetation, will be highly reflective of near-infrared wavelengths and so appear red, while bodies of water absorb the wavelengths and appear black. Other features vary in the color that they appear as, and so the map can be used to understand various aspects of the terrain. This Color-infrared aerial photograph is of the Chausey Islands in France taken at low tide, as was taken to observe patterns of seawood.