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by dualogy
3428 days ago
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DEMs: how high-res do you really need the DEMs, how many petabytes will you sacrifice for sub-meter accuracy? Unless the app is for mountaineers, what's out there for free in lower-res (to be interpolated by varying to-be-experimented-with smart algos/heuristics throughout academia) and affordably handle-able on a global scale [1] should be a perfectly sufficient starting point until users actually complain about minor inaccuracies. Whether we're talking 30m or 90m resolution.. it's not "high" but for all sorts of startups but the most exacting surveying/etc pro-level b2b offerings, a fine starting point. (Of course I'm only talking DEM here, since you mentioned them, whereas Lidar proper kinda covers details such as houses and other structures as 3d points.) [1] http://viewfinderpanoramas.org/dem3.html seemed to be the best in the "free" (for prototypes / MVPs and such) space when I last played in this space on-and-off from 2011 through 2014~ish. |
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In late 2015, I spent a couple weeks researching GIS data conversion utilities, Cesium's formats, and potential improved source datasets we could use to generate higher-quality imagery and terrain data. I can't haul out the relevant writeup atm, but I concluded that the EarthEnv DEM90 dataset appeared to be highest-quality free terrain source I could find ([0]), and the TrueMarble collection was the best free imagery source ([1]).
I generated our earlier terrain dataset using the Cesium-Terrain-Builder utility ([2]). It generates Cesium's "heightmap" format, but does not yet support the "quantized-mesh" format. I have seen a couple other tools that appear to deal with quantized-mesh tiles, though. On my list to dig into at some point.
As a related note, using the MBTiles format ([3]) for storing and moving tile datasets around is great. Multiple gigabytes in a single SQLite database file (or possibly a few files split by zoom level), rather than trying to move around millions of individual 10KB images on disk. Highly recommended.
[0] http://www.earthenv.org/DEM.html
[1] http://www.unearthedoutdoors.net/global_data/true_marble/dow...
[2] https://github.com/geo-data/cesium-terrain-builder
[3] https://www.mapbox.com/help/an-open-platform/