Aerial imagery has long been a staple of GIS. By providing viewpoints from high above the ground, aerial images enable people to understand the geographic context of individual features. Orthoimages developed from aerial photographs routinely serve as background maps of terrestrial data for numerous GIS applications. GIS analysts use photogrammetry to develop terrain models and measure specific objects or features. Airborne remote sensing using infrared wavelengths supports GIS in the study of vegetation and thermal characteristics of natural or built objects.
When combined with other data in a GIS, aerial imagery supports a more complete, accurate analysis of a scene. As an example, forest managers can identify areas where homes and buildings are close to overgrown or unhealthy forests that are susceptible to wildfires. The foresters can work with local agencies and property owners to mitigate fire risk and develop emergency plans.
To obtain aerial imagery, GIS professionals can turn either to third-party service providers or in-house resources. Most commercial aerial imagery is captured using manned aircraft equipped with sophisticated cameras or lidar, depending on the type of application and imagery needed for a project. Manned aircraft are typically operated by service providers and offer important benefits such as the ability to cover large areas and fly at high altitudes as well as capture very-high resolution images with advanced, large-format sensors. The results are excellent, but come with tradeoffs. Costs for manned aircraft can be high, and jam-packed flight schedules or changing weather conditions can introduce risk to expected lead time for collection and processing of aerial images.