Surface melt detection in Greenland
Hello,
I am a researcher experimenting with cryospheric applications of Planet imagery. Specifically, I've been working on validating algorithms for surface meltwater detection and supra-glacial lake volumes against estimates made with Landsat, and then using the high spatial and temporal resolution of Planet Doves to learn about patterns of surface water flow and abrupt lake drainage events. I'm posting for two reasons - first, to see if there's anyone else in the forum working on something similar (in which case, I'd love to hear about what's working and what's not!), and to throw out a suggestion for a way that Planet imagery could make a bigger impact on my field.
Most of my work focuses on the edges of Greenland, so the 4-band imagery that Planet has available is very valuable. However, there are a few specific areas on the edges of Greenland - namely ~5 large, important, and well-studied outlet glaciers (Jakobshavn, Petermann, 79 North, Kangerdlugssuaq, and Helheim, to name the primary players), that Planet's acquired imagery almost covers but misses. These are not far enough north to be in the pole hole; it appears that the acquisition in these areas just stops near the edge of the ice sheet, as with the rest of Greenland.
Studies in my field would benefit greatly from a small expansion of Planet imagery acquisition to cover these areas. Do you know if there is any plan for such expansion in the future? Have the images been acquired in those areas and just haven't been processed? I realize that Planet's overall goals may not align with this sort of research, but I thought it might be worth inquiring in case Planet is looking for this sort of suggestion. I think a small change could make a big difference in cryospheric research.
Thank you for your time!
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Hi Karen,Thanks for your important question. Planet is working to improve not only image production in the cryosphere, but the appearance of browse images for cryosphere regions, which currently often appear over exposed (even while the underlying analytic products are typically better exposed).Importantly, we do actually collect imagery over the whole of Greenland with the same density that we collect over, say, Iowa. Indeed, because it is higher in latitude, the actual image density in Greenland is often higher than in Iowa. The gaps you're seeing at the edges of the ice sheet are due to rectification failures, which means we are unable to assemble the data into a band-aligned 4-band multispectral product. The good news is - if you set your filter to include '3-band PlanetScope' - you will see much more imagery. You can look at imagery density overall, by either 3-band or 4-band product, using the 'cover' tool which is a map icon in the lower right corner of Explorer.Here's an example of the interior just East of the Jakobshavn calving face:Although these 3-band images have less spectral depth, they are often well exposed with water ponds visible and isolated in the red channel.We also working to update our visual color products for cryosphere regions in Explorer. Many of the images you will see appear to the naked eye to be 100% white or overexposed, even though they are typically better exposed if you download the analytic products. We expect a fix on this in the near term, and we’ll let everyone know here at Planet CommunityJoe & the Planet Team
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