Thread: GPS Advice
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Old 05-01-2017, 08:43 PM   #29
ndoggac
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Join Date: Jul 2014
Posts: 21
I agree regarding the efficiency of vector data vs raster. That's why vector maps are so useful for mobile! Unfortunately for my uses, vector data is typically not very useful.

Most of the work I've done with mbtiles has been documented here on my website for navigating Stillwater Reservoir. See the "Offline map tiles" section on the main page, and the "Available Imagery" link at top left. Any time I find new imagery, step one is to package it up in an mbtile file and a KMZ file (if possible) so I never lose it. You never know when online repositories will go away (eg. Mapquest Open Aerial). I do all my map data creation (routes, hazards, etc) in QGIS. Mbtiles load up very easily and quickly into this program, and I can stack imagery layers based on water height.

Besides the satellite and aerial imagery I've located, I've also created a custom depth map of the reservoir, which is also available in mbtile, as well as KMZ.

I don't really make "custom" maps with MOBAC, I just create the offline repository with it, or sometimes GlobalMapper or Maperitive depending on the source of imagery. To make the custom map, I use QGIS.

For example, in QGIS I could load up one of the topo map mbtiles, set the satellite imagery over top of that, but only show it over the topo inside the shoreline of the reservoir. Then add the depth map over top of that, but at 50% opacity so you can still see the satellite imagery underneath, and export it all as a brand new mbtile file. You could also integrate in vector data, like routes, polygons, etc into the final mbtile export file. I usually avoid this since it can easily be done in the apps, and you never know how you'll want to mash up that data on site. I can take paper maps (link on site) and create an overlay for them as well.

If the mobile apps allowed loading up multiple mbtile files at once with varying opacity levels, I wouldn't have to create the custom maps. I haven't figured out a way to achieve this yet though. Maybe there's a way?

If you want to try out QGIS, there's a quick guide on my site, albeit a pretty simple one. It's a great tool, and is pretty easy for basic stuff, but can get really complicated fast since it's so powerful. One of my favorite things to do is to download the "DEM" elevation data for a region from here and create my own topo maps, typically with much more accuracy than the old pre-made topo maps. The DEM data is also raster data similar to satellite imagery, but the pixels in the imagery are encoded with elevation information, rather than color information. The data is often created using LIDAR, which is very accurate. Lots of cool stuff you can do with this program, and there's a ton of free source data.

Last edited by ndoggac; 05-01-2017 at 08:46 PM.. Reason: fixed
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