Search And Rescure GPS Command

[alias2187]

Hello,
The down and dirty. I want to use RPI to link teams together for Search and Rescue. They will give their GPS coordinates, relay back to a server, and then all the teams locations will be displayed on the Grid map. If you have done S&R you would understand how beneficial this is to make time tables, and for support allocation. Most places do not have cell service, and we do not have the money for satcoms, or this would be easy.
Concept: I want to start off with 4 teams. Each team will only have one RPI. The RPI will have LCD screen, gps and wifi (yes the battery packs will be large for now) . Each RPI will get it's gps data every 3 minutes and overlay that position on the projected map on the LCD ( I am not sure how to do this yet as most map programs are online). Then it will save the data to a time index file.
We have strong 2.4ghz directional antennas that are mobile, along with battery powered access points (and one Arial drone that has a AP). The RPis connect with the wifi when they can, ssh (or whatever protocol I wish) the time stamped gps files back to the command server. Also the command server will relay all the data that it has about the other teams back out to the other RPI's and it will populate the maps on the RPi's. The command server will be able to display all information on a local monitor.
I would also like to send commands I.E take this search grid, go this way to search etc, but that is way farther than I am thinking now.
So the questions really are (besides how am I going to make the local area network in mountains) what GPS software would be best to use? It has to be lightweight, able to be used offline, and be able to be customized by color for each team. is it even viable? It is great in theory (in my opinion), but practical application has yet to be seen.

[paulie]

Alias,
Not sure where in the world you are, or what previous experience you have of search & rescue.
Radio Amateurs have been using APRS, using amateur frequencies for many years.
I use Xastir (which runs on the Pi) to plot stations on a map.
Various devices can be set up (including TNC's [to interface with radios] and GPS).
It's possible to set up 'digipeating' so you rebroadcast other stations (subject to decreasing number of 'hops').

Obviously to use Amateur frequencies you would need a licence to transmit, but it might be possible to use licence-free spectrum.

There are Amateur groups who self-train in message handling in preparation for disaster relief ( check your national amateur radio organisation for examples [RSGB in UK, ARRL in USA etc.]).

I wouldn't recommend going 'out into the wild' unless you know what you are doing, so you avoid becoming a casualty yourself.