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Author Topic: Any downside to loading a single IMG for a region vs. many?  (Read 2095 times)

erobillard

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Some sites like OSM let you either download a single .img file for a region (state, province, etc.) or to get the same region as many small files. I don't have a shortage of memory, and many small files seem much harder to manage, especially if I get more than a couple regions that way. I tried subfolders in the Garmin folder (using an eTrex Touch 35) to organize these regions on my MicroSD, but it doesn't seem to see a file unless it's right in the Garmin folder.

So is there any real downside for performance or anything else with using the large files instead? Or a way to better manage the smaller files so I don't end up with a thousand in the Garmin folder?

Cheers,
-Eli.

Boyd

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Re: Any downside to loading a single IMG for a region vs. many?
« Reply #1 on: July 21, 2019, 03:08:47 AM »
It depends on the exact regions you are loading. But your GPS has a limit to the total number of map tiles (aka "segments") that can be accessed. This limit has nothing to do with the size of the files, it is related to the number of little tiles that are inside them. There are no standards for the size of a map tile, it's up to the mapmaker - a tile could cover a whole county or only a few city blocks.

In practical use, most Garmin devices will exceed the tile limit with only about 4gb of map files. You can use Javawa device manager to see how many tiles are in the maps you have loaded. The limit applies to all tiles on your device - it's the total of what is stored in internal memory plus the SD card. Doesn't matter whether the maps are enabled or not.

http://www.javawa.nl/jdm_en.html

Your eTrex has a maxium of 4,000 tiles

https://support.garmin.com/en-US/?faq=m1lBmDidNX8VV7Oc44vVZ8

So you may find that one big file has too many tiles to work properly, and using smaller map files will give you more control over this. If you have too many tiles on your GPS, some of the maps will not work properly. THere's no way to predict what will happen, it depends of the specific maps you're using.