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After I install one of the pre-compiled OpenStreetMap (OSM) sets for say, North America, how will the new OSM data interact with the existing data? I've listed some scenarios below and filled in my current best guess:
In addition, I've noticed that sometimes, when I try doing a OSM website search for an address that has a house number, OSM will not be able to pin down the exact coordinates. How will those situations be resolved? Model Information
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Using an GPSMap 78 I experienced that addresses and POI are found for both maps - you get two results. It doesn't matter which map is active. But the device doesn't show directly which result is from which map. In some cases looking directly at the resulting POI you can tell from the format of the additional information if it is from Garmin or from OSM data. Note that older garmin devices can only handle a single gmapsupp.img file, so that only a single map can be installed at a time.
(07 Jan '13, 14:38)
Vincent de P... ♦
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This does depend on just what maps you are using. All maps in Garmin format have a "draw priority" set, and they may be set as transparent. The map with the highest draw priority will be shown on top. If the map is transparent, then any lower maps will also be visible. If you are generating maps yourself using Mkgmap, then there is an option to specify the draw priority and set transparency. I don't know if its possible to adjust this on Garmin maps, or pre-compiled OSM maps. |
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I ended up trying this out and found that the Garmin device uses different maps with no apparent rhyme or reason. Basically, it's not a good idea to have 2 active maps when trying to generate a route or view the map. |
Different Garmin devices work in slightly different ways - it would help to say which ones in particular you're asking about.