This project came out of a very simple need; the need for speed. The night before I was leaving on my road-trip across the Grand Canyon, I realized I didn't have my Garmin with me. So I hacked this together. However, I have since realized I absolutely love the simplicity of this thing. There's a certain freedom in just pushing a button, being sure that your tracks will be recorded and dealing with everything else later on.
I know what you're thinking. Isn't there an app for that? Well, my three part answer to that is that apps crash, phones die and A-GPS(the kind of GPS used in phones) doesn't work everywhere. I learned this lesson the hard way.
The idea is pretty simple. I have two main components, a GPS unit that sends the current GPS location over serial and Openlog from Sparkfun which takes a any incoming serial data and writes it to a microSD card. To access the data, just pop the microSD card into your computer and open the file using Google Earth. Easy as pie!
Step 1: Get Set!
Here's what you need:
* OpenLog datalogger
The easiest way to log serial data!!
* GPS unit
Selected for it's small size
* AA battery holder
* AA Batteries
* Slide switch
* microSD card formatted to FAT16/32 (not in picture)
Step 2: Make It!
There really isn't much to describe. I removed the 4 pin connector as it was taking too much space. Then, using some jumper cable I soldered the following connections:
GPS OpenLog Battery
I drizzled entirely too much hot glue over everything to make sure it was (slightly) water resistant.
That's it! Put a formatted SD card in OpenLog, flick the switch and you're in action. Switch it off and there's no battery drain. Every time you switch it on, OpenLog creates a new file in the misroSD card, storing all the data the GPS is sending.
Step 3: Use It!
When you first switch on the unit, you will note that a blue LED blinks on the OpenLog, this indicates that the unit is functional and recording data. If it stops biking, it's time to replace the batteries. I measured the current draw to be 55mA on average. With a 2000mAh AA battery, that would be just over 36 hours of continuous use.
When you first switch on the GPS it can take a solid 15-20 minutes to get a fix on the location. I would suggest powering on the GPS and leaving it outdoors for an hour the first time you use it. Then verify that you did indeed get a fix on your location. After this, as you use it normally, it would get a fix within 10-15 seconds.
The logs are stored as numbered .txt files "LOG00001.txt", "LOG00002.txt" so on. But the data is actually in NMEA format. So, to open the data in Google Earth you have to rename the file to ".nema". So "LOG00001.txt" becomes "LOG00001.nmea". You can then open it in Google Earth by just going to File>Open and browsing to the file.
You can get creative with it and use tools like MapBox to make some amazing roadtrip scrapbooks!