Moin allesamt, it seems I have been poking around a long standing issue. Sorry for raising so much dust.
If I understand right, the issue comes from the lossy compression making terrain data a little blurry, and also introducing artefacts at those high contrast areas that do only occur between 'no data' points and 'real data' points. That does not affect the continually raising higher areas very much, but it is an issue for the edge areas at +/-10m MSL or so. Further, I think this is true: 1. In TIFF there is support for layers, including transparency. 2. Also, TIFF must not necessarily be uncompressed, AFAIK compressed layers can be embedded. 3. There is a 'water' overlay already available as a vector and as a pixel image file. I could imagine that the manipulation of the data should if possible be done on the map gen level rather than on the device. That would allow going on using compressed data for the terrain files on the device. In the uncompressed data, it appears possible to locate the precise coastline, and if during compression all data below coast line could simply be moved say -100m, then the blurryness would not have the depth to reach as deep. That does, however, not solve the coastal interpolation artefact mountain issues. These would only go away if either a lossless compression was used, or if the contrast was reduced. If the sea was not defined as an almost endlessly deep area, but it's depth limited to say -100m, the interpolation artefacts could possibly be reduced to an acceptable amount and the terrain representation as used today could possibly stay in place, only using a pre-calculated image file. Using a compressed TIFF instead of a JPEG2000 could also be an approach worth investigating. The data is not much bigger, though an alpha channel, or simply a 'sea' mask overlay could be used. This way, lakes at any given altitude could also be precisely displayed as water. Besides this, I can imagine some more future applications for a multi layered map file. Viele Gruesse, Martin --- Am 29.12.2010 um 10:16 schrieb Tobias Bieniek: > Good idea in general, but the JPEG2000 image is grayscale without any > transparency and if I'm not entirely mistaken transparency isn't > supported by JPEG2000. (at least I haven't seen it anywhere yet...) > > But keep coming with the ideas :) > > Turbo ------------------------------------------------------------------------------ Learn how Oracle Real Application Clusters (RAC) One Node allows customers to consolidate database storage, standardize their database environment, and, should the need arise, upgrade to a full multi-node Oracle RAC database without downtime or disruption http://p.sf.net/sfu/oracle-sfdevnl _______________________________________________ Xcsoar-user mailing list Xcsoar-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xcsoar-user
