Originally Posted by
Steve B.
Agree, just buy a cheap SD card, throw it in, then follow the DCRainmaker directions. It’s very easy and gets you maps as good as what Garmin would sell you. Note that the 810 came loaded with useless maps with no detail, Garmin expected users to buy maps from them, but allowed the OpenSreetMaps to be used as desired, which is what everybody does.
Many (if not most) bought the 810 with a bundle that included the map (making the map cost about $50). One problem is that you have to pay to get updates.
The "useless map" is the world basemap. It is somewhat useful for areas where you don't have detailed map coverage. It also makes screen updating faster at low zoom levels.
Garmin didn't really allow the OSM maps to be used. They had no choice.
What happened is that people reverse engineered the img file format years ago. They wrote two programs that take OSM extract data to create img files.
Garmin sold people maps in this format (the topo maps might still use this format). Preventing units for using this format would have really annoyed their customers.
Garmin has a new img format (called NT) that hasn't been reverse engineered.
The Garmin "City Navigator" (CN) maps (what Garmin sells) don't have cycling-specific information (like cyclepaths). The OSM maps often do.
Garmin now includes the OSM maps on newer units (at no extra cost).
That works because it gives cyclists more appropriate maps and the OSM maps don't cost Garmin anything (unlike the CN maps that cost Garmin a lot of money to produce).