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As of now, I have limited internet data and want to consume as less as possible. Downloading OSM data for offline editing seems to be relatively small compared to the background imagery tiles, since these are images. But I want to map some rivers and roads so I will need to use some imagery. Are there any tips to conserve data when using JOSM? Should I flush the tile cache? Also, will using DigitalGlobe Premium Imagery conserve more than the Standard version? (I am assuming the Standard offers raster tiles and Premium vector?) |
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In fact JOSM caches imagery by default. have a look in your imagery settings in section/tab "Cache") to see the sizes. I currently have around 500 MB of imagery on disk - just from using JOSM and viewing imagery. I guess that JOSM does not re-request recently cached imagery tiles and hence does not consume your internet data volume. I have just tried it with JOSM running from a console window: if I switch on a certain imagery (e.g. DG Standard) JOSM downloads the imagery tiles - in the log in the console I see many http requests with a 200 response and a size. If I close that imagery layer and open it again I see many http requests again - but this time with a 304 response and no size. Meaning that JOSM did not download again because the server responded that I already have the most current version. Just the metadata was transferred which needed only about 1 kB for each tile - instead of around 56 kB for each tile. JOSM's tile cache seems to persist across restarts. In addition: You can tweak cache settings in the expert settings of JOSM if you really need that. Regarding your "flush" question: no, you should not do that. Because that would mean that JOSM deletes all already cached/downloaded tiles meaning that the next time you need them, you need to download them again. |
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Caching the imageries locally in the first place (ideally where there's limitless, fast internet connection) and pointing JOSM to the cached location e.g. one of the methods outlined by an Indonesian OSMer. However, there's a Catch-22: you should respect the bandwidth limits (not caching a very large area) or risk getting access cut in the future (T&Cs still apply). P.S. it would be fantastic if, let's say, DG reps themselves commented here and confirming that caching things locally is fine. |
No. Premium does not offer vector images. These are both satellite images, shot by a "special" ;-) camera on Earth orbit.
https://en.wikipedia.org/wiki/Vector_graphics
Aside from Premium being maybe clearer or being shot in better conditions, these are equal from point of view of this problem.
... in fact in my area in Germany "Standard" is much better than "Premium". Just compare both to see which one is better.