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Hello OSM friends, made my first experience with exporting mapniks (and osmarenders) as JPGs to use in a handheld GPS device (software: GPS Tuner Atlas, converts JPGs to its own .gmp or .gma format (topographics)). Actually, it works quite fine for my purposes as hiking maps, but I'm still unaware, to use following the optimal procedure. E.g., I select an area at zoom factor 8, set the max size to 1:13500 (as indicated) which results in a JPG size of 1890x2076 px exported. Processing the JPG by the software and upload to the handheld works fine. But is this the best result (in terms of image resolution) I can obtain? Sorry for asking this primitive basics, but I'm an absolute newbee in this area. Thanks a lot for any advise. Sincerely Friedhelm Achenbach |
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If your software ("GPS Tuner Atlas") supports also PNG, then this is the better choice because PNG is lossless and JPG is not lossless. This means that with JPG you might have higher compression rates but lower quality in terms of artifacts in the image. As a rule you can say that JPG is not good for maps. Hello ALE, thanks for your fast reply. I'll give it a test. GPS Tuner Atlas seems to support this file format. Sincerely, Friedhelm Achenbach Königswinter, Germany
(15 Mar '11, 17:39)
achenbach
If it has worked for you, then please accept the answer (and hence make the question green).
(17 Mar '11, 11:18)
ALE
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In terms of resolution this is of course not the best you can achieve. If you render your own maps you are in theory not limited to any zoom level by the software, but in practise you are of course limited by the map detail that is actually available for your area. To get your own rendering there is various software, e.g. Mapnik (the one used on the main page of OSM, not the easiest way to do it but nice antialiasing and collision detection, reads OSM-files directly but not with standard stylesheet, requires to install a postgres database and load the data into it for bigger areas), Osmarender (reads OSM-files directly, must split bigger areas into parts) and Maperitive (is said to be the easiest way, also reads OSM-files directly). For all of them you can download stylesheets developed by the comunity to not start from scratch. |
