Over the summer Gabriel Mahler has been conducting research on hedgehog habitat mapping using Agent Based Models (ABMs) and remote sensing. Hedgehogs seem to like brambles and so as part of his work he has produced a bramble map. He did this by combining the TESSERA earth representation embeddings (using the geotessera library) with data from iNaturalist. The current model is an ensemble of logistic regression and a knn classifier.
Can we really see brambles from space? What better way to test the model than a quick field trip around Cambridge. Gabriel, Anil, Shane and I did just that today.
Gabriel's model overlaid on a map - which was quite hard to read in outdoor sunlight
We started at Milton Community Centre, as the model was relatively confident there were brambles near the car park and along the path to Milton Park. It took us about 20 seconds to find the first one in an area indicated by the model.
Our first bramble!
So it turns out that there's a lot of bramble between the community center and entrance to Milton Country Park. We stopped six or seven times before reaching the park entrance. While the model predicted we'd find brambles all over the park, we went for the few areas of very high confidence near the entrance. In every place we checked, we found pretty significant amounts of bramble.
Some bramble on both sides of the path near the park entrance
Trying to navigate using the model
I was fairly sure it was in that direction (and thankfully it was)
We collected photos of all the places we stopped, as well as recording our GPS location. One thought while out exploring is that the model did a great job predicting where we would find very large quantities of bramble without any cover. It didn't have high confidence in other areas where we found smaller brambles under partial cover. Since TESSERA is learned representation from remote sensing data (Sentinel 1 and 2), it would make sense that bramble partially obscured from above might be harder to spot. This is something we can potentially tease apart when we have more validation data.
... continue reading