“A principal aim of geospatial analysis is examining and understanding change over space and time. One of the simplest yet most powerful things you can do in ArcGIS desktop (www.esri.com/arcgis) or in ArcGIS Online (www.arcgis.com) is to visualize change over time by studying change based on different basemaps created on different dates.
For example, I recently conducted a GIS workshop for educators at Northeast Junior College in Sterling, Colorado. While on campus, in ArcMap, I added satellite imagery as well as the USGS topographic map. I determined the date of the topographic map (1971) by accessing the USGS Map Store. I found the date of the satellite imagery (2009) by using the Identify tool in ArcMap on the imagery layer. I used the swipe tool so I could scroll back and forth across the map to easily compare the different basemap images.”…for more information and the full article by Joseph Kerski click here