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| Developers' Corner General World Wind development. |
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#1 |
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Junior Member
Join Date: May 2009
Posts: 2
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Hi DSTile gurus,
I've run into an odd problem with what_nick's win32 port of DSTile. It seems to skip over several tiles that contains almost solid colors or very near black images. Specifically, I'm tiling the BMNG data and it will not produce a tile for specific areas in the ocean where the whole tile is solid dark blue. This entire exercise is more of a learning process for me, and in the last few weeks I've gone from a new user to tiling for WW. Here's the blow by blow of what I'm doing: 1. I've got the WW cache pack of BMNG tiles as a reference. 17,051 files for January. 2. I went and downloaded the "world.topo.bathy.200401.3x21600x21600.p anels.png" source files from NASA and wanted to re-tile them. 3. Using gdal_translate, I reprojected them as GeoTIFF files using the following commands: Code:
gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr -180 90 -90 0 world.topo.bathy.200401.3x21600x21600.A1.png A1.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr -90 90 0 0 world.topo.bathy.200401.3x21600x21600.B1.png B1.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr 0 90 90 0 world.topo.bathy.200401.3x21600x21600.C1.png C1.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr 90 90 180 0 world.topo.bathy.200401.3x21600x21600.D1.png D1.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr -180 0 -90 -90 world.topo.bathy.200401.3x21600x21600.A2.png A2.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr -90 0 0 -90 world.topo.bathy.200401.3x21600x21600.B2.png B2.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr 0 0 90 -90 world.topo.bathy.200401.3x21600x21600.C2.png C2.tif gdal_translate -of GTiff -a_srs "+proj=latlong +datum=WGS84" -a_ullr 90 0 180 -90 world.topo.bathy.200401.3x21600x21600.D2.png D2.tif 4. Now I fired up DSTile (using FWTools version 2.3.0) and used this command: Code:
dstile tile --lztsd 36 --wwcache --png --overviews output_tiles A1.tif A2.tif B1.tif B2.tif C1.tif C2.tif D1.tif D2.tif I went to compare a few tiles and found that most of the tiles there were not produced are in the middle of the ocean. The jpg version in the tile pack show these tiles are very plain in content. Some are almost completely full of blue pixels (colored r:2 g:5 b:20) with maybe 5 pixels of a slightly different shade blue (colored r:2 g:5 b:22). A few examples can be found in this folder: "BMNG (Shaded + Bathymetry) Tiled - 1.2004\4\0012". There should be 160 tiles, but my test only produced 132 tiles. A few that are missing include: 0012_0025, 0012_0029, 0012_0030, and 0012_3032 to 0012_0035. Several other folders contain a few missing files here and there around the globe, but they all share the same characteristic of having little to no data other than a solid color. I've tried re-tiling using jpg and got the exact same results. Same files are missing from level 4. I've tried re-tiling using FWTools 1.4.2 (the same version DSTile was built alongside), but with the same results again. What am I missing here? Why does DSTile or the gdal tools it uses not output those tiles? Oh, and "Hi" World Wind Central. I must have spent the better part of the last 2 weeks reading postings here learning about Tiling and Serving data for WW. Awesome collection of knowledge! |
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#2 |
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Administrator
Join Date: May 2006
Posts: 32
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Colors below certain value are used to indicate transparent areas and if a tile would be all transparent it is omitted. You need to either preprocess the input data to not contain near-black or modify dstile sources to reduce the color value.
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#3 | |
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Junior Member
Join Date: May 2009
Posts: 2
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I decided to try and modify dstile for this purpose, but I can't seem to get it to compile and run in VC 2008 Express edition.
I haven't made any changes to what_nick's code yet. I'm just trying to compile his version and get it to work. Currently the binary that I compile just crashes when I try to use it. what_nick's pre-compiled binary works fine with the same syntax. If anyone knows why my compiles don't work or can help me with getting what_nick's windows port to compile, I'd be grateful! Here's what I originally wrote: Quote:
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