Ultimate GPS breakout accuracy issue

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melaboudi
 
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Ultimate GPS breakout accuracy issue

Post by melaboudi »

Hello,
I'm connecting an Adafruit Ultimate GPS Breakout (https://www.adafruit.com/product/746) to an Adafruit Feather 32u4 FONA (https://www.adafruit.com/product/3027).

The Fona gets the coordinates from the GPS and sends them over GPRS to our server (Traccar) every 5 seconds.

Everything works perfecly fine, however, sometimes I get very innaccurate coordinates (off by 10s of kilometers).
For example: Instead of getting a latitude of 34.268574 i get 34.000000 and then everything goes back to normal (See yellow circle in the attached picture).

I'm using a fully charged 2500 mAh battery and a CR1220 coin cell battery in the back of the GPS breakout.

Please help!

Thanks.
Ultimate GPS Issue.png
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dlleigh
 
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Re: Ultimate GPS breakout accuracy issue

Post by dlleigh »

The GPS coordinates that you're seeing appear to glitch to an even number of degrees in latitude. That seems like a software problem.

Whatever is reading the NMEA data from the Ultimate GPS is occasionally having problems and cutting off the data after the decimal point.

This is highly unlikely to be a problem with your hardware.

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melaboudi
 
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Re: Ultimate GPS breakout accuracy issue

Post by melaboudi »

Thank you dlleigh for the reply.
You are right, this might be a software issue. However, yesterday the same software was used to send over 3400 perfectly accurage GPS points to the sever.
Moreover, If it's a software issue, then both the latitude and longitude should be wrong.
Any ideas ?
Route.png
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dlleigh
 
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Re: Ultimate GPS breakout accuracy issue

Post by dlleigh »

A software glitch could easily affect only the latitude and not the other coordinates.

It is difficult to conceive of a hardware glitch that would affect the latitude measurement, exactly on even degrees, without also messing up the longitude, altitude and a bunch of other measurements.

Can you record the NMEA output and post that here? It will give us a lot of information about the nature of the problem. We should be able to verify the exact data in every field and see what the software sees. You may need to hook the Ultimate GPS up to a computer to do this, instead of having it connected to the FONA.

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adafruit_support_carter
 
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Re: Ultimate GPS breakout accuracy issue

Post by adafruit_support_carter »

Agree that this seems like a software issue somewhere. See if you can recreate it in a simple setup that does not have the FONA involved.

Can you share your full code you are using with the FONA?

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