Garmin and EGNOS

A little while ago, I bought a Garmin GPSmap 60Cx to replace my Garmin GPS 60. The GPSmap 60Cx provides (as the name implies) mapping functionality, and it also has the very sensitive SiRF III GPS receiver that the GPS 60 did not have.

The sensitivity of the GPSmap 60Cx is spectacular compared to that of the GPS 60: I can get a fix indoors, and outdoors the EPE rarely ever gets above 5 meters CEP.

However... whereas my GPS 60 happily picked up the EGNOS (WAAS for Europe) signals at Garmin channels 33 and 39 (and sometimes 37), the improve the accuracy to 1 to 2 meters CEP, the GPSmap 60Cx bluntly refuses to use these signals. The unit recognises _very_ strong signals on channels 33 and 39, but then decides not to use it after about 30 seconds. After some discussion and searching on the internet, it seems that EGNOS currently still sends out a "testing" flag in its correction signals. The GPS receiver in the GPS60 would happily use the signals anyway, but the SiRF III firmware in the GPSmap 60Cx actually honours the testing flag, and thus (correctly by design) refuses to use them.

That may all be very well according to the standards, but my experience with EGNOS has been very good on the GPS 60. I would therefore like to use it on the GPSmap 60Cx as well, and I'm willing to take the risk of these signals not being 100% reliable.

Now, it seems that it is possible to force some chipsets into using testing signals anyway, as posted here. However, it is not clear whether this will work with the SiRF III chipset as well. In addition, these commands seem to work on a serial link only, while all I have is a USB cable, and my laptop has no serial port.

We'll see...