The RVRV can also be implemented in a helicopter, fixed-wing aircraft, or watercraft. A powerful feature of ER Mapper is the ability to combine multiple data sets into a single data set of many layers, then query the cells in those layers using algebraic and Boolean functions. Cady took 1990 US Census Data of the Denver metropolitan area and converted them to logarithms in Excel so that they could be accurately expressed as 8-bit grayscale images in ArcView. These were exported to ER Mapper and georegistered. Topographic relief is greatly exaggerated.
Orange lines are county boundaries.
The spreading orange and yellow areas show the suburbs of Denver sprawling out into former farmlands, shown in blue. Suburban growth selectively moved onto the higher ground, mainly stream terraces, while industrial areas concentrated along the Platte River and Clear Creek. Figure 2 shows the change in housing density from 1939 to 1949 superimposed on shaded relief topography illuminated from the west. The colors show the increase in housing units per square kilometer from 1940 to 1949 on west facing slopes of more than two percent . Cady's working hypothesis was that fine homes would be concentrated in areas of moderate buildout, shown in blue and yellow, where individuals could buy choice lots in advance of mass development.