[Gabriel] put together an impressive writeup of his autonomous catamaran, Atlantis(PDF). It was certainly done as an academic project, but there's a thorough explanation of the math logic behind the control systems. The heart of the boat was a waterproofed Pentium laptop with a CAN bus parallel interface used to talk to everything on-board. Sensors included GPS, wind, hull speed and rudder angle. In case the site can't handle the load, I've mirrored the 1.4MB PDF here.

Since water blocks the radio frequency used for GPS triangulation, GPS is considered pretty useless for SCUBA divers. Apparenlty some of them are finding it useful to waterproof off the shelf units for tracking the beginning and end of dives. (Dives in open water often involve currents that can really move you along.) To avoid any wiring, a floating case is used. When the diver wants to grab a waypoint, he/she lets the gps surface for a short while to acquire a fix. Then the diver can pull it back down and mark the waypoint or record the coordinates.

It's been a while since we talked about putting a GPS on top of a D200. [Rick] sent in his latest version. He used a nice 20 channel sirf III gps from spark-fun, a cheap D200 remote cable and a few parts to send the NMEA sentences down the wire. The biggest improvements include taking the $100 Nikon cable out of the mix and swiping power from the camera for the GPS board. All the info is there, but I had to seriously stare at his wiring instructions for a while despite the low parts count. I like to see actual circuit diagrams!

[dgoeken] sent in his Magellan 3100 hack. The device runs Windows CE 5.0, and mounts as a standard flash drive. Since everything is easily accessible, it's just a matter of replacing and modifying the appropriate files. According to the GpsPassion message board, some are finding his guide useful for other models of Magellan GPS. So far he's added a file manager, media player and upgraded the Points of Interest file. The site is slightly bandwidth challenged, so I've mirrored his hack process here.

[superlopez] sent in this detailed article (mirrored here and here) which describes how to build a GPS and GLONASS (the Russian version of GPS) receiver. The resulting device is gigantic compared to one of those tiny bluetooth USB GPS units, but the ability to build one's own receiver is one of those post-apocalyptic skills I sure would like to have. The creator of the article [Matjaz Vidmar] aka [S53MV] also has pages on Packet-Radio (PKT) transceiver improvements (PKT gets my vote for the best post-apocalyptic technology, and the only believable technology featured in the Transformers movie), and a more sophisticated homemade frequency counter than the one featured earlier this summer.

In 2005 we featured a from-scratch GPS receiver as well, thought the project site seems to be down. If your GPS unit just needs a better antenna, check out [Will]'s how-to from last year.

[leatix] sent in this one after seeing the weather balloon logger the other day. In this case, it's built around a Mega8, stores the log on a MMC/SD card and runs on a LiIon battery. Translating it was a bit problematic for me, but give it a shot if you feel lucky.

[Stefan] sent in this data logger that was built for a weather balloon project. It's a very clean design that logs to a 64KB eeprom, can transmit its location via SMS through a cell phone and trigger a camera based on position if needed. The site has a tarball will full schematics and source - mod away.

[Nick] caught [Alex]s GPS enabled AVR, so he sent in his project using the same Telit GM862 module. Rather than depend on an external AVR, he wanted to use the on-board python interpreter. Apparently, documentation is a bit sparse, so he put together a good write-up on developing python for the device. Since the GPS unit takes up the com port previously used for debugging info, he added a hardware python debugging board to speed development.

[Alex] sent in some of his latest work. He interfaced some not so cheap components to give an AVR GPS and GSM I/O. For now it can read the GPS position and send text messages. Thanks to the GPS/GSM module, the schematic is pretty simple - anyone with basic soldering skills and a desire to put a dent in their credit card can probably build this. (Programming the AVR is probably the most difficult task)

We don't normally chase after commercial products, but when I ran across this guys work, I was impressed. My favorite has to be this solar powered GPS logger. It logs your trek to a SD card and it's oh so tiny. Other notable projects include a li-poly battery backpack for charging USB devices. (Li-Poly batteries require some specialized charging)

Hack-A-Day friend [Limor] AKA [ladyada] has been promising a portable RF jammer for a while. guess what she sent me for Christmas? The Wave-bubble is a self tuning RF jammer - good for around 20 feet of RF enforced peace. (It outputs .1-.3 watts) With a pair of less efficient antennas, it even fits inside a pack of cigarettes. She'll never sell these because the FCC would come-a-knockin, but if you've got some major skills, you might be able to build one. (I'm going to believe her take on this, I've seen her work in person and it's some damn fine stuff)

Merry Christmas! Get your Design Challenge entries in today!

Kevin Zeits sent in his diy Nikon d200 gps cable and hot shoe gps mount.
Nikon sells it for $150, but has a 3 to 6 month eta. Ok, it's really just a ttl to rs-232 converter with proprietary connectors - but I love tagging photos with gps info. Now if only I could do this for my canon rebel xt. (It would take a firmware hack at the minimum) If you're not blessed with a d200, check out gpsphotolinker.

A Radiosonde is an inexpensive sensor package that's intended to be used with a weather balloon for atmospheric measurements. The device transmits data in the 403 MHz band after being launched and they usually aren't recovered after use. You can pick them up for very little money on eBay so [Nick] thought they might work well as a low cost GPS tracker. Unfortunately the Radiosonde doesn't transmit standard NMEA GPS data, but GPS doppler measurements. It's hard to determine what those are actually useful for. Nick did find one other paper documenting an unsuccessful attempt which he has posted to his site. So now Nick is looking for some help either making the data more useful or coming up with a functional device that's just as inexpensive. Anyone got any leads?

This Russian site has all the details needed to upload new maps to a Magellan eXplorist 300, 200, or 100. Inside the battery case are four pads that can be used for serial communication. You will have to use a MAX232 to shift the voltage levels. Since this occupies the battery space you'll need to provide power as well. This can be tapped from a USB port. Once the cable is built you can download waypoints using OziExplorer.

[thanks Chris, Cary for corretion]

Automatic Position Reporting System (APRS) is used to transmit location and other real-time data over amateur radio frequencies. [Scott Miller]'s OpenTracker project is designed to encode the NMEA data from a serial GPS receiver for transmission. It doesn't have to be used for GPS telemetry though, you could hook up a weather station or any other remotely located project. Scott has boards, parts and even full kits available.