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I need Long/Lat and also angle of a vehicle to the North at the same time. I found I can use GGA message to extract Lon/Lat with no problem. However it doesn't give me the angle that I need.

Then I found RMC message and seems to be what I'm looking for. The problem is I'm not sure if the Lon/Lat in both messages are the same? also if 'Track angle in degrees (True)' is the angle to the North?

Thank you in advance for sharing your experience or ideas.

For your observation:

RMC message:

https://www.trimble.com/OEM_ReceiverHelp/V4.44/en/NMEA-0183messages_RMC.html

enter image description here

Barry Michael Doyle
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1 Answers1

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Track angle (field 6 in RMC) is the direction the vehicle is moving, not necessarily the direction it faces, although for a ground (wheeled or tracked) vehicle these are very likely the same.

Yes, it's relative to true north.

Testing whether two pairs of Lat/Lon coordinates are equal or not is a rather trivial thing.

Octopus
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  • Thank you for the reply. I'm working on a ground vehicle and all I need is to distinguish between moving right/left and forward/backward besides knowing the Long/Lat at each point. So I think RMC should be the right choice for me as you said. About testing, I don't have the vehicle in hand at the moment that's why I was looking for someone who might have similar experience to share. –  Feb 24 '17 at 22:09
  • Looks to me like Octopus is talking about the direction the vehicle (GPS gadget) is moving however what @Mechatronics is talking about a solution to this problem: calculate the lat/lon of each of FOUR POINTS whose common distance from the gadget is known and whose bearings from the gadget are repectively 0, 90, 180, 270 degrees. See prev post http://stackoverflow.com/questions/42402913/gps-data-estimation – John Machin Feb 24 '17 at 22:59
  • @John Machin. Well no, that's a completely different question. The moral is there is no way to know the orientation of a GPS. Only a delta from a previous position. If it rotates in place there is no way to know from GPS data alone. – Octopus Feb 24 '17 at 23:03
  • @John Thanks for the comment. I think I'm good to go with your help about that topic. Now the question is about getting Lat/Lon and also 'direction of the vehicle' at the same time. As Octopus said as well, I think RMC message should contain both information that I need, but I'm not sure if the Long/Lat data format and also number of decimal points in GGA and RMC are the same or not ... –  Feb 24 '17 at 23:07
  • I added a picture for more clarification. All I need to know is Lon/Lat at each point, and also the angle my vehicle is moving. –  Feb 24 '17 at 23:14