For the altimeter I used SCP1000-D11-PWB since the sensor itself is a SMD which you can't solder yourself. BUT the altimeter is really not needed since practically all the new bluetooth GPS modules support GSA NMEA data and therefore they also give you the altitude of your plane. I have already written a version that fully supports GSA and is able to have 3D waypoints. I'm also going to write a X-Plane based simulator for the NXT AutoPilot which is going to work over bluetooth SPP.
The code is made for RobotC which you 'have' to pay for but I'd recon it's worth it eventhough RobotC is still quite buggy.
If it's THIS GPS module you're referring to it ought to work just fine with NXT. The thing you need with NXT is SPP (i.e. Serial Port Profile).
RobotC is really simple and powerful once you get the hang of it. You don't really have to worry about the altitude aspect of the GSA and 3D waypoints as I'm going to post soon my vastly improved NXT AutoPilot code along with the simulator.
If you're using my AutoPilot code you will note that there's a variable in my code that's called "GPSName" and it is set to "HI-406BT". You ought to replace that HI-406BT with your GPS device's name, which you can see if you pair your GPS with your computer. The AutoPilot will then connect automatically to the GPS when you start it. I'm actually right now going to make a test flight with my new NXT AutoPilot version and if the flight is successfull I'm going to release the first non-BETA version of the code..
Are you absolutely sure your GPS won't work? Could you tell me how is it not working so that I might be able to help? My GPS is rather expensive due to some additional features I have on it but for NXT UAV use THIS GPS ought to be quite perfect; it has a definable refresh rate from 1hz to 5hz and a logging cabability! It also supports bluetooth SPP so it should work with NXT just fine..
Here's some info on how to setup the current version of the NXT autopilot:
-You need to determine a so called "velocity factor" for your gyros since every gyro has a velocity factor of it's own. I'll publish a program that'll determine this factor automatically along with the first non-beta of the NXT AutoPilot within 3 weeks (atlast - hopefully).
-You need to set EPAs and other stuff for your servos.
-You need to set your PID coefficients
-You also may need to alter the accelerometer code a little according to the attitude you set your accelerometer compared to your plane. (Nothing too hard.)
To help you with these settings there's a "Test Assembly.c" file along with my AutoPilot code with which you can test that the attitude of the plane is read correctly before you try to load the actual autopilot to your NXT.. The test assebly code, however, requires the right sensors to be connected to the right ports on the NXT..
Other than that there are some things which also need some knowledge of before you try to fly with this AutoPilot. I'm more than happy to help you with them to try and ensure your success with this autopilot once you're ready to start to assembly it.
Don't know about that bluetooth GPS of yours then. Luckily that iBlue 747 A+ is a sure bet to work with NXT if you don't mind an extra bluetooth GPS, although a good one.. ;) BTW here's something you could try: Can you pair your NXT manually from the NXT's bluetooth menu with that GPS module of yours?