Now that we have taken over 2,000 photos of Tasman Glacier, it's time to use them to produce the DEM of the glacier. There are a few different softwares out there that combine photos into three-dimensional models, but we're presently using AgiSoft PhotoScan Pro. With only one laptop cranking away, the reconstructions take a fair amount of time (20-30 hrs for approx. 400 photos), but the results are rewarding.
Below is the 'dense point cloud' produced from the 400+ photos taken on our first drone flight. We were stationed on the edge of the moraine in the lower left (not shown in this image), and the glacier is flowing towards the bottom of the image.
Upon zooming in, one can see a pretty amazing level of detail. For instance, the image below shows that we've captured the three-dimensional structure and layer in a region of debris-free ice on the glacier. For reference, the feature is approximately 100 meters wide.
The information going into the DEM production is both the photos and the location (x, y, z) of the drone when the photo was taken. To ensure that our DEMs are accurate, we will create them without any 'ground-truthing', which in this case is a separate dataset of ground control points (GCPs) that we also took while in the field. A GCP is an accurate GPS measurement of a notable feature (either natural or man-made) that can be seen in the DEM. We can then pick these features out in the DEM, and compare their location and elevation to that which we measured in the field.
We hope to have more cool images soon -- and we will be giving more details about some of the specifics that went into the hardware and software of this campaign.