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Using Remote Sensing for Mapping and Counting Animals

by Tejaswi Bhardwaj

The GIS and Remote Sensing data have been brought to use for wildlife observation in particularly for geological mapping of animals’ count in remote locations, in the raising concerns over endangered animal and bird species’ population. The use of low cost Unmanned Aerial Vehicles (UAVs) and highly accurate aerial LiDAR mapping services and digital terrain models have brought an advancement in the geological mapping techniques.

Thermal and infrared satellite imagery has helped improve counting by relating animals’ heat and visibility signatures to given reflectance. Ground observations and GPS data have been used in conjunction with digital aerial triangulation to help validate observations and geolocate detected animals such as white-tailed deer in one study. Supervised classification can then be applied to create signatures that are then applicable for wider areas where less control might be available (i.e., lack of ground observations).

Fig 1  IMAGE © J.HODGSON  Imagery showing Aerial View of a seabird colony compared with the ground counter’s viewpoint    

Despite the fine scale benefits of UAV counting, there are problems. The main critique of detecting and counting animals has been that studies have mostly focused on relatively small areas, such as small parks or enclosures, whereas there is a greater need to count over very wide areas. In fact, this is one reason why it has been difficult to determine how well some endangered or threatened species are doing, such as polar bears. There is a greater need to expand studies, enable long-term monitoring and change detection, and better develop automated or semi-automated methods and classifications so that signatures could be counted accurately. In effect, this is still an area that needs further research and work. 

Using Satellite Data to Map Species
The satellite-based data have been used widely for counting of phytoplankton growing in lakes and water systems but was confined for smaller species. Using the Medium Resolution Imaging Spectrometer (MERIS) platform, which absorbs phycocyanin at around 620 nm, the system can detect sensitivity and robustness of phytoplankton growth. This makes satellites such as the Envisat, an older but still utilized system, useful for large area surveys. In effect, satellite-based data have so far been better at conducting such large area survey relative to UAVs, as most UAVs operated by biologists likely have limited range and flying time.

 
Fig  2  IMAGE © J.HODGSON   Drone Derived Photographs and the ground counter’s view 

Ecologists are increasingly using drones to gather data. Scientists have used remotely piloted aircraft to estimate the health of fragile polar mosses, to measure and predict the mass of leopard seals. Drones have also been labeled as game changers for wildlife population monitoring. Counts of birds in drone derived imagery were better than those made by wildlife observers on the ground. The drone approach was more precise and more accurate as it produced counts that were consistently closer to the true number of individuals. 


Use of Aerial View and Drones to count birds
The researchers found the estimates made from the images captured by drones were consistently similar or larger than ground-based counts. There was less variation in the number of birds identified by people trawling through the photos. 

 
Fig 3  Images captured by a drone of a colony of nesting crested terns

The downward facing perspective of drone imagery reduces the likelihood of missed counts due to topography and birds obscuring the counters' line of sight. Drones can provide a more precise picture of nesting seabird colonies than traditional methods used in wildlife conservation, according to an Australian study of polar and tropical birds.

Key points of drones for birds counting:

  • Drones reduce the likelihood of missed counts due to topography and birds obscuring the counters' line of sight
  • Estimates made from drone captured images consistently similar or larger than ground-based counts
  • Fixed wing drone captured images of royal penguin colony on Macquarie Island
  • The study, published in Nature Scientific Reports, highlighted the potential of unmanned aerial vehicles (UAV) to survey birds and other animals, particularly in remote areas.

 
Fig 4  Drone images of this colony of royal penguins (Eudyptes Schegeli) were more accurate than ground based counts

Summary
The world is rapidly changing, with many negative outcomes for wildlife. Technology like drones can help scientists and managers gather data fast enough to enable timely assessment of the implications of these changes. When monitoring wildlife, increasing the accuracy and precision of animal surveys gives us more confidence in our population estimates. This provides a stronger evidence base on which to make management decisions or policy changes. For species and ecosystems threatened with extinction or irreparable damage, such speedy action could be a literal lifeline


SATPALDA is a privately owned company and a leading provider of satellite imagery and GeoSpatial services to the user community. Established in 2002, SATPALDA has successfully completed wide range of photogrammetric and Remote Sensing Projects.

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