Hi all,
I have recently started a quadcopter project where my end goal is to fly a quad with DGPS. I am just in the beginning stages of this goal and have recently purchased a GPS but am having problems with the data I receive from it.
At present I have a ublox LEA-6T that I hope to mount on my drone. However, the GPS is not giving me valid data; it is finding satellites in view yet provides no fix. Here is an example of what I am receiving:
$GPVTG,,,,,,,,,N*30
$GPGGA,,,,,,0,00,99.99,,,,,,*48
$GPGS99,,,,,,*48
$GPGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*30
$GPGSV,3,1,12,01,,,22,02,,
$GPRMC,,V,,,,,,,,,,N*53
$GPVTG,,,,,,,,,N*30
$GPGGA,,,,,,0,00,99.99,,,,,,*48
Can anyone offer any advice on how to get valid data? I have downloaded u-center but am unsure what to change to get a fix.
I would greatly appreciate any help!
Replies
With a good view of the sky it shouldn't take more than a minute or two max to start computing a position.
More of the $GPGSV sentence is needed to be sure, but maybe there is a problem with the antenna or its connection.
The data for PRN01 shows no elevation or azimuth and only a SNR of 22 which is really low. If the other satellites have similarly low SNR values then that is the problem. Reasonably good values should be in the upper 30s or higher.
How do we increase the SNR values?
We are really new to this field and appreciate your help!
More info is needed to help. Some complete $GPGSV sentences once the receiver has been powered up for at least a minute in an area with a good view of the sky would be very useful.
It looks like the Ublox module is on a home made board in the picture you provided. It's easy to get something wrong in the support circuitry or have a poor connection somewhere. It's also possible that another component is causing interference. The SNR values will shed light on this.
The type of patch antenna you are using typically performs better with a ground plane underneath it. Any flat piece of metal several cm across (or more) will help. This shouldn't be required to get a fix though. Something else is causing problems.
You need to put it close to a window or better still go outside with a clear view of the sky for 15 minutes or so.
Thanks for your help Gary, however this data string is taken from long message thread of 25 minutes. All the messages were similar and there was pretty much no variation over this time period. The GPS was outside in a courtyard.
Do you have any other further suggestions?