Civil authorities are increasingly taking to UAS-based mapping owing to flexibility in operation, lower costs and ease of use
UAVs (Unmanned Aircraft/Aerial Vehicles), or as most civil aviation authorities now call them, UASs (Unmanned Aircraft Systems), are attracting a lot of attention lately from geospatial professionals. The common questions being: “What applications can I use it in? What benefits can it provide to my organisation or my clients (or data users)? And, how do I implement such a system in my organisation?”
High-level system description & capabilities
Typical UASs available today are equipped with wide-angle RGB cameras that f ly about 100m above the ground. More options are being offered, including near-infrared photography. The typical system runs on electrical power and f lights are between 30 and 60 minutes in length. Depending on the endurance and speed of the aircraft, typical coverage is around 1-1.5 sq km (100-150 hectare) at 5 cm GSD.
UAS image processing is usually done using close-range photogrammetric techniques adapted to exposures taken in flight. Th is technique allows accurate construction of photogrammetric models which approach, and often surpass, the quality achievable with much more sophisticated manned aircraft systems flying at much higher altitudes. With these technologies, photomosaics, orthophotographs, digital terrain models (DTMs), digital surface models (DSMs) and point clouds can be established. Without ground control, the models have high, centimetrelevel internal consistency in X, Y and Z. With sparser ground control than is typically required for conventional photogrammetry, good-quality models registered to the ground control can be rapidly generated at much lower costs than most other methods of achieving similar results.
UAS are not a panacea for all mapping issues. Satellites, high-altitude photogrammetry and LiDAR, and ground-based techniques all have their place. But geospatial data managers will be surprised to see how nagging problems — as well as some they didn’t recognise as problems — can be solved with UAS-based mapping.
A big benefit of UASs is that it can be used on land and water, or on environmentally compromised sites. Low mobilisation and processing time means not having to wait until the ideal time for conventional photogrammetry. Because of much lower operating and data processing costs, UAS can be used to do updates where it was previously cost-prohibitive with other technologies.
»Disaster management: Updates on flood maps and other types of baseline maps, when changes become apparent at ground level, can be quickly mapped with UAS. Further, there could be spot-checking of areas known to be of interest and updating in near realtime, short period visitation to get updates on progress of fire, f lood or to monitor evacuation routes for traffic management. In addition, UASs are useful as a baseline for emergency response services. Better information, often obtained under conditions that would be impossible for other technologies, can improve quality of life of those affected and reduce negative economic impact of the disaster. Emergency management benefits from near on-demand mapping updates.
» Natural resource management: UASs help in broader and deeper assessment of yield potential before making lease or purchase investments in addition to giving a better outlook for accurate ROI determination for businesses. For governments, early and more complete information means better planning.
» Flora and fauna: UASs can help in studying migration, territorial studies of fauna and f lora ecosystems, monitoring endangered species, bird nest monitoring, environmental assessment, and detecting habitat stress. Forests are a major natural resource in many countries and regions. UASbased mapping that is project- or incidentfocused has a real place in safeguarding inventory. It helps in easy determination of the location(s) of where the pest or disease problem exists, often without actually visiting the infected location. For example, personnel can be directed to cut down trees using GPS locators, without having experts along to make a final evaluation. Once a “prescription” has been carried out, success can be monitored by closely spaced f lights at little additional expense.
» Mining: From multi-temporal monitoring and mapping of headwalls, to tailings and other areas disposed to subsidence or collapse, and slope and wall failures, UASs can be used extensively in the mining sector. Th is can help with prediction of hazardous events to prevent failures or to avoid exposing personnel to danger. Mining monitoring can be on a closely spaced schedule that far outperforms other technologies.
» Construction: The development of large sites and engineering projects necessitates expensive ground-based surveys or aerial photogrammetry. With UAS-based mapping at regular intervals, managers can have a true picture of the site. Change detection software can be used to monitor changes on a regular schedule, with outputs to various types of reporting systems to monitor costs vs progress; cost vs quality, etc.
UAS-based mapping provides f lexibility unsurpassed by other technologies. Portable equipment that can function in a wider variety of adverse weather means that mapping can be done closer to the time of need. Because mobilisation and f light cycles are short, f lights can be done hourly or more frequently in urgent situations such as f loodwater or fire tracking. Cloud cover is rarely a problem as the UAS f lies under the clouds. In fact, in some parts of the world, it is considered the only mapping tool for aerial mapping as the weather, availability of aircraft, other equipment and trained personnel rarely coincide to allow opportunities for conventional aerial mapping. When focused areas need to be mapped with timely generation of data products under conditions — weather, hazard limitations, or closely spaced visitations — that test the capabilities of other tools, the selection and successful use of UAS in such situations is only limited by the solution-provider’s creativity.