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Project #009 - DakarOSD/Lynx RC Plane OSD - Page 8 - Google Earth


One of the additional functions of the LYNX board is a serial output containing NMEA data and that can be hooked up to a laptop on-site and used display/log your flight movements live in Google Earth!

Google Earth does have built in functions to read NMEA data, but only at 4800 baud, and with some other limitations. So, the way around this is to use a separate standalone program to read the data from your laptop COM port and pass that data to Google Earth, and also letting you configure a whole lot of parameters along the way.

Note: If you are using my LYNX Pcb then you will not need an external TTL to RS232 converter as the serial signal from the Lynx board is already boosted (the standard Lynx Pcb from Cristobal has a simple TTL output and thus requires an external booster).

Here is the wiring of the cable (9-way D-type free sockets) when using my Lynx Pcb. Laptop (left) to Lynx (right):

2 -------------------------- 3
5 -------------------------- 5
4 link to 6
7 link to 8

So back to the standalone programs. There are any number of these apps, however I only found two off them to date that seemed to work with the Lynx NMEA serial output. These programs read the NMEA data and convert it to KML data files that Google Earth can read real-time. As follows,

Franson GpsGATE 2.6  (available here).
GEtrax (available here)

The following example setup is using GEtrax. After installing the app configure the following parameters from the pull-downs:-

COM Port Number = usually com1 if you are using a laptop.
Baud Rate (NMEA) = 57600
Program Mode = Real-time Location (NMEA)
Output to Google Earth - checked

Next, here's a screenshot of GEtrax, and with the preferences I have set up.
You can either set up GEtrax to auto load Google Earth when it starts up, or wait for user input. My preference is for 'Auto' start as below. The rest of the preferences are self explanatory.

The next thing to do is to check that valid data is actually reaching GEtrax. Pressing F12 will bring up the debug window where you should be able to see the actual NMEA messages being received. As follows:

If you get this far then you are nearly ready, however, before you actually drag your laptop etc to the field, you should complete full ground testing first. I found that even in my back garden I was able to walk around with the plane and it would record some movement in Google Earth.

The following screenshot is the system actually running. The DakarOSD & Lynx are both operational, the NMEA data is being input via the com port of my laptop, GEtrax is work and the data is being fed to Google Earth. When Google Earth starts up it should immediately direct to your current GPS position and trace your movements. I was testing from my back garden as base, so the screenshot below is my street! Sorry you can't see many 'traces' as I wasn't moving around much!
Look closely you can see a wee plane around the centre of pic.