The limit is on the maximum file size (about 2GB per file) and available storage memory. Good enough for our work, but you might consider a deeper tool if you need more raster data than that at a time.Theoretically, the Garmin Nuvi GPS navigator can be loaded with hundreds of map. Well, Garmin doesn’t want you to load more than 100 tiles (probably for performance reasons), but what does that mean practically? For the testing I did, that meant for a 4 foot pixel (most of our best data isn’t more spatially accurate than that, even if it’s more precise), I was able to load about 3200 acres– enough for one of our larger parks. Just choose KMZ as your output type, choose one of the garmin types in the next screen, and the rest easy easy GUI fun. Now, you can use MapTiler to generate the kind of KMZ that is so near and dear to the garmin’s heart. Easiest hand crafting of geographic data you can imagine (it’s the gateway for bigger and better hand crafted geographic data).

You can export an image from any desktop or server package, and if you know the upper left coordinate of the image, and the pixel size, you have enough to create a world file. You can follow Garmin’s directions, but if you already have georeferenced data, skip them and by whatever means you know, generate a jpeg with a world file (for you ArcMap users, goto data view, file:export choose jpeg, and check the world file checkbox). Sure enough, it came in, and we’ve loaded them.

None-the-less, when a colleague told me that Garmin now has firmware support for custom maps for some of it’s GPS units, I told him it might be a good choice for his field work and that I’d work on loading our maps onto his unit when it came in. A GIS Manager who doesn’t have a GPS is it’s own category of silly. I don’t spend much time on field equipment, e.g.

Garmin custom maps size limit