> On Sep 30, 2014, at 17:12, Alec Ten Harmsel <a...@alectenharmsel.com> wrote:
> > >> On 09/30/2014 10:05 AM, meino.cra...@gmx.de wrote: >> Suppose the GPS would already be attached >> to the board and works... >> >> Is there any free available software and data for >> strict offline useage (which does NOT calls >> to home), which is able to map GPS data to a street/land >> map? >> I need both: The maps themselves and the logic to read >> GPS coordinates and map movements and ways to those maps. >> >> Is something like that available for free or should >> I directly ask the NSA/CIA/FBI/...? >> >> Thank you very much in advance for any help! >> Best regards, >> mcc > The only project I know of that has openly available map data is > OpenStreetMap (openstreetmap.org). I know they have an API, and they > probably (not sure) have maps available for download. > > afaik the only way to combine various map data out of the box is to use > a GIS package like QGIS. You can write software to do this using the > proj4 library for an embedded box, not sure if anything for your > specific use case already exists and is open source. > > Alec Sorry iphone send mail even if you don't wanna :/ What you are considering doing is quite a challenge. What kind of coordinates does your gps module give you? The gps system works with cartesian x y z coordinates. Then these are usually displayed to the user in WGS-84. This is a quite hard mathematical problem (differential elliptical problem). Usually is done by your gps receiver and is approximated. GIS libraries have these functions built inside. Distances are easier and faster to calculate in cartesian coordinates. You need to calculate distance because coordinates from gps will never coincide with any address. Open street maps provides a very good start, but addresses have great differences in different countries. For example google misses addresses quite much depending on where you are searching. Getting the address right requires good locality from the program. Addresses and roads are vector maps. The fastest way to get address is to have the vector map of the world and then calculate distance to the closest address. The database will be huge :) Maps are usually raster pictures which have some projection. When you display them you can use 3d or 2d visual. In 3d (like google earth) you draw a sphere (or oblate spheroid) and draw textures on top of is to the right coordinates. In 3d everything needs to be converted to cartesian coordinates. Or in 2d you decide a projection and then convert the projection of your maps to this projection. After that it is just easy drawing. GIS libraries contain all the needed tools for these operations. There are a few of them with open source license. I have been doing some work with opengl 3d drawing maps. Good luck your project is quite big but it is sure very much fun :) -- -Matti
