Hello everyone!
Just wanted to share two papers that we published recently on approaches to deal with counting errors when surveying wildlife populations using drone-derived orthomosaics..
In the first paper, we draw attention to some unintended counting errors that may arise specifically when building orthomosaics when animals are moving during the flight, and we discuss some strategies to mitigate these errors and potential solutions for further explorations.
In the second paper, we develop an approach to estimate the abundance of aggregated wildlife populations from orthomosaic counts, taking into account multiple sources of variations (entries and departures of individuals during the sampling period, availability during flight, double counts..). We apply this approach to estimate the population of Giant South American River Turtles during a mass nesting event, what resulted in the description of the current world's largest known aggregation of freshwater turtles.
Hope it is useful and I would be happy to receive any feedback! =)
Ismael
Brack2025 - Counting animals in orthomosaics from aerial imagery_0.pdf Brack2025- Estimating abundance of aggregated populations with drones turtles_0.pdf26 July 2025 6:59am
Thank you for sharing. Would love to learn bit more about the data workflow.
Last year I tired to using QGIS and few existing models to count the birds from orthomosaics of wadding birds in Cambodia but gave after dismal results.
Nahuel Emiliano Farias
Instituto de Investigaciones Marinas y Costeras (IIMYC-CONICET/UNMDP)
10 February 2026 8:13pm
Great papers, thanks for sharing!
We’ve been using drones to detect color-tagged crabs in saltmarshes, which allowed us to achieve a 60% recapture rate—something that was impossible with traditional trap or sampling methods.
By comparing orthomosaics captured at consecutive time intervals, we managed to re-detect individuals and quantify their movement for the first time. However, our detection process was done manually by eye.
I’m now looking into automated detection. Do you know of any existing tools that could be adapted for tracking color-coded targets across sequential maps, or would you recommend developing an ad hoc solution?
Best,
Nahuel
Arky