Urban Sprawl
G E O W O R L D / J A N U A R Y 2 O 1 0 24 Imagery/LIDAR Special Issue Chang e Detection H istorical aerial imagery is a valuable primary data source that allows users to peer into the past to help manage the present and improve the future. By looking at multiple snapshots in time, important ques-tions can be examined from a historical perspective. Urban sprawl, for example, has occurred in varying degrees since the Industrial Revolution. The causes are many, including poor planning, increased access to transportation networks and the basic desire to live fur-ther away from central urban areas. By comparing cur-rent to historical aerial imagery, changes due to urban sprawl can be quantified and spatially analyzed. Visualization of change over time can provide insight into land-use patterns and change processes. Change detection is a type of analysis that examines an object or landscape feature at different points in time to determine what and how much it has changed. Some physical landform changes (e.g., coastal erosion) are more gradual than changes in land use (e.g., rural to urban). The benefit of having an extensive historical record is that many types of change can be observed. Capital Changes Historical imagery recently was used to illustrate change detection in Sacramento, Calif. The area of interest borders the Sacramento River near the pres-ent airport in the north and the Pocket-Greenhaven area in the south. The project compared imagery from 1958 to 2009 to see how rice production and general agricultural land use was affected. Imagery used in the study area varied by year. Black-and-white imagery was used for 1958, 1964, 1972 and 1998. Color infrared imagery was available in 1984 as well as four-band multispectral imagery for 2009. BY JOAN BIEDIGER AND LOUISE MATHEWS S prawl How Is It Affecting America's Ranch and Farmlands?