Since offline use is my primary motivation for getting into APRS, I feel like I need to figure the maps as an important step. But the good news is I feel like I am getting a lot closer to understanding the steps and gear needed.
Warning - this question may make no sense, but I will ask anyway. Can I take my ScenicMap files and run them through some process (mapsforge?) to make them OSM? It is a bummer that they are iOS only, but I like the look and feel of ScenicMap.
Or it might be best to just start with the KS9N OSM file and see how that works for starters...
Are ScenicMap maps vector or raster? I'm not familiar with it. IOW, are they a bunch of topographical tiles at different zooms?
Mapsforge is a vector map display format, Open Street Maps is the database (OSM information is like ESRI Shapefiles). Raw OSM data are just geospatial points and their vector relationship. Maps are built from the information in the OSM database but the data itself has no meaning without a set of rules to define things like "these set of points are a road" and a file to define what a "road" actually looks like on the screen.
For OSM-to-mapsforge the typical software is Osmosis and Osmconvert. AFAIK the resulting mapsforge file is a binary, so you'd be trying to derive source files from a compiled application. There's no 1:1 relationship between the code you wrote and the end product of the compiler.
Raster maps are digital representations of actual things using a bitmap. There's no relationship implicit in the file, you are showing with pixels just exactly as possible how it really looked. Using the wrong decoder ring (rendering engine) is like displaying an image file with a text editor, you just get ASCII hex instead of an image. Raster maps are convertible to some extent as long as you know datum, size, scale and resolution. That is like converting from TIFF to PNG. OSM data can be made into raster maps if that's what is required.
But a couple of things come to mind. First, there's no reason to use stale data for an OSM map. The OSM database is continually updated and so a new map from it should be built with the current database. It's open source and free, so there's no reason to bother trying to use an existing map as a source.
Second, any application using mapsforge won't know what to do with raster data, so unless they are vector maps to start with there's no easy conversion that will make meaningful outputs. Or they may be proprietary, like Garmin IMG, so no one knows the magic tea leaves.
Point I'm making is not to try to re-engineer what's already done with OSM maps and mobile/portable packet radio. If there's no obvious way to use your existing maps getting new ones extracted from the database costs nothing.
The root problem, though, isn't the maps. It's that every application wants its own format and none of them do everything. Backcountry Navigator is the closest but it wants it own topo maps, is an incomplete APRS application and marginal navigation and poor waypoint management (but does render mapsforge, which is nice). APRSdroid lacks any navigation or routing ability and can't do offline raster. Gaia doesn't do any APRS. aprs.fi is still a beta IMO and also has no navigation. Oruxmaps works pretty well but the routing is clunky relying on Brouter and only does APRS-IS, can't talk to a TNC as near as I can tell. It's a Charlie Foxtrot.
