Modern approaches to airborne imaging provide flexibility and efficiency in GIS data acquisition. 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.
How is aerial imagery traditionally captured?
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. Whether anticipated or not, lead times can affect the value of the data. If imagery can’t be captured and processed when needed, conditions on the subject site might change, reducing stakeholders’ confidence in the data they rely on for decisions and actions.
Speed and flexibility for GIS data collection
The emergence of small unmanned aircraft systems (UAS) for GIS brings new options into the picture. Companies that need aerial imaging can own and operate a UAS or hire a UAS service company at a tiny fraction of the cost of manned aircraft. Small UAS can be transported by vehicle to a project site, where they take off and land from an area smaller than a basketball court. An on-site operator controls each flight using a tablet or laptop computer, significantly reducing flight time and costs for pilots and airborne camera operators.
Small UAS can operate at low flight altitudes, often flying roughly 120 m (400 ft) above ground level (AGL). The low altitude, combined with high-resolution digital cameras and slow flight speed (80 kph or 60 mph) enables UAS to provide good resolution and precision. Users can achieve ground sample distance of 5 cm (2 in), which is sufficient for detailed mapping and terrain modeling. Low-altitude flight also means that UAS are less susceptible to weather. By operating near the ground, UAS fly beneath cloud cover that frequently hampers high-altitude photography.
The speed and flexibility of UAS significantly reduces lead times. UAS flight plans can be pre-programmed and then loaded into the aircraft during pre-flight setup. For applications requiring repeated flights over an area, flight plans can be reused, enabling the autonomous aircraft to replicate previous flight paths and locations of photo stations. This repeatability adds efficiency in applications for change detection and land use mapping, wetlands, riparian areas and measuring material volumes in construction, landfills or mines. Images and flight data can also be downloaded immediately after the flight.
Like other data collection solutions, UAS offers a choice of sensor platforms. In selecting a UAS technology, GIS professionals should consider the applications and information needed. Fixed-wing aircraft efficiently cover large, open areas and are used in applications such as forestry and agriculture, cadastral mapping and natural resource management. For imaging over smaller or more confined spaces, a multirotor UAS provides excellent agility and flexibility. It can operate in mountainous, urban or industrial environments, collecting data for applications including inspections, change detection and compliance.
UAS: A new mainstream solution
The flexibility of UAS provides several important benefits for GIS applications. It enables users to collect high-resolution imagery from low-flying aircraft, which produces excellent precision and ground sample density. The low cost and rapid deployment makes it economical to conduct data collection missions more frequently, allowing users to collect data more frequently. The temporally-dense data is important in tracking changes in buildings and vegetation as well as monitoring construction and earthwork.
Potential users of UAS should be aware that current regulatory environments for commercial use of UAS vary from country to country and in some cases can be quite complicated. Civil aviation authorities around the world are working to define and implement rules that allow safe operation of these new platforms within their airspace. To ensure compliance, UAS operators need to know and understand the rules in their countries and operational regions. As UAS continues to take hold around the world, the business opportunities will expand. UAS will give a significant competitive edge to proactive companies. As you look at your operation, it’s likely that you will discover ways that UAS can help your business. Opportunities like this don’t fly past very often.
Ron Bisio, vice president, Trimble