Ultimate GPS Breakout Inaccurate
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- wsen18
- Posts: 3
- Joined: Thu Jan 01, 2015 11:46 pm
Ultimate GPS Breakout Inaccurate
I purchased the GPS breakout a while back and am just getting around to using it. I set it up by following the Adafruit tutorial. Everything appeared to work, but after cross-checking the coordinates with multiple coordinate finding utilities online, I found that the coordinates from the GPS were off. It is considerably more than the 3 meter accuracy shown in the specifications. Is there anything i can do to fix this?
- Franklin97355
- Posts: 23911
- Joined: Mon Apr 21, 2008 2:33 pm
Re: Ultimate GPS Breakout Inaccurate
Can you post some output from the serial monitor? Also are you inside or out?
- wsen18
- Posts: 3
- Joined: Thu Jan 01, 2015 11:46 pm
Re: Ultimate GPS Breakout Inaccurate
I was outside.
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- GPS Serial Monitor Output.txt
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- adafruit_support_mike
- Posts: 67446
- Joined: Thu Feb 11, 2010 2:51 pm
Re: Ultimate GPS Breakout Inaccurate
There are two classes of error in GPS readings: precision errors (large jumps between readings from the same position) and position errors (consistent numbers that map to some other location).
I see one hiccup in the last reading, but the others seem to be fairly consistent. Which category of error are you seeing?
I see one hiccup in the last reading, but the others seem to be fairly consistent. Which category of error are you seeing?
- wsen18
- Posts: 3
- Joined: Thu Jan 01, 2015 11:46 pm
Re: Ultimate GPS Breakout Inaccurate
There is a position error.
- adafruit_support_bill
- Posts: 88093
- Joined: Sat Feb 07, 2009 10:11 am
Re: Ultimate GPS Breakout Inaccurate
It would be helpful if you could be a little more specific. What is the difference between the position reported and what you believe to be the correct position?
Most 'position errors' are due to a misinterpretation of the data format.
https://learn.adafruit.com/adafruit-ult ... ter-wiring
Most 'position errors' are due to a misinterpretation of the data format.
https://learn.adafruit.com/adafruit-ult ... ter-wiring
People often get confused because the GPS is working but is "5 miles off" - this is because they are not parsing the lat/long data correctly. Despite appearances, the geolocation data is NOT in decimal degrees. It is in degrees and minutes in the following format: Latitude: DDMM.MMMM (The first two characters are the degrees.) Longitude: DDDMM.MMMM (The first three characters are the degrees.)
- jigawatt
- Posts: 26
- Joined: Tue Apr 17, 2012 5:38 pm
Re: Ultimate GPS Breakout Inaccurate
I'm getting inaccurate position readings too. It seems to be consistently off about a mile or two in the E-NE direction. Isn't the GPS Library code handling all the parsing of data? I'm creating new variables to store new corrected values for Long and Lat offset.
- adafruit_support_bill
- Posts: 88093
- Joined: Sat Feb 07, 2009 10:11 am
Re: Ultimate GPS Breakout Inaccurate
Please post an example of the errors you are seeing.
- jigawatt
- Posts: 26
- Joined: Tue Apr 17, 2012 5:38 pm
Re: Ultimate GPS Breakout Inaccurate
The example code I would post would look very similar to the guy before. The issue is that if I put coordinates in google earth, the position says on the map that I'm about 10-12 blocks away from where I actually am.
I read this:
People often get confused because the GPS is working but is "5 miles off" - this is because they are not parsing the lat/long data correctly. Despite appearances, the geolocation data is NOT in decimal degrees. It is in degrees and minutes in the following format: Latitude: DDMM.MMMM (The first two characters are the degrees.) Longitude: DDDMM.MMMM (The first three characters are the degrees.)
"this is because they are not parsing the lat/long data correctly." Isn't the parsing being handled in library code? The _.MMMM part is a little off. This is the value I'm offsetting the. I subtract something like .2500 for N and .0250 for W (I think, as I dont have the code in front of me... at work)
After looking at his closer I'm noticing this:
$GPGGA,051955.000,3000.5935,N,09532.2458,W
Location: 3000.0000N, 9532.2460W
$GPGGA,051957.000,3000.5935,N,09532.2458,W
Location: 3000.0002N, 9532.2460W
$GPGGA,051959.000,3000.5936,N,09532.2458,W
Location: 3000.0004N, 9532.2460W
$GPGGA,052001.000,3000.5938,N,09532.2459,W
Location: 3000.5937N, 9532.2460W
First three sets are off but looks like the last one printed correctly, Kinda wish he would have let it run a little longer :)
I read this:
People often get confused because the GPS is working but is "5 miles off" - this is because they are not parsing the lat/long data correctly. Despite appearances, the geolocation data is NOT in decimal degrees. It is in degrees and minutes in the following format: Latitude: DDMM.MMMM (The first two characters are the degrees.) Longitude: DDDMM.MMMM (The first three characters are the degrees.)
"this is because they are not parsing the lat/long data correctly." Isn't the parsing being handled in library code? The _.MMMM part is a little off. This is the value I'm offsetting the. I subtract something like .2500 for N and .0250 for W (I think, as I dont have the code in front of me... at work)
After looking at his closer I'm noticing this:
$GPGGA,051955.000,3000.5935,N,09532.2458,W
Location: 3000.0000N, 9532.2460W
$GPGGA,051957.000,3000.5935,N,09532.2458,W
Location: 3000.0002N, 9532.2460W
$GPGGA,051959.000,3000.5936,N,09532.2458,W
Location: 3000.0004N, 9532.2460W
$GPGGA,052001.000,3000.5938,N,09532.2459,W
Location: 3000.5937N, 9532.2460W
First three sets are off but looks like the last one printed correctly, Kinda wish he would have let it run a little longer :)
- adafruit_support_bill
- Posts: 88093
- Joined: Sat Feb 07, 2009 10:11 am
Re: Ultimate GPS Breakout Inaccurate
Post the GPS coordinates you are getting from the breakout and the coordinate you believe to be correct for your location.
Also check your Google Earth configuration. Google Earth supports a variety of coordinate formats. You may not have it configured for the Degrees/Decimal Minutes format that is standard for GPS.
https://support.google.com/earth/answer/148070?hl=en
Also check your Google Earth configuration. Google Earth supports a variety of coordinate formats. You may not have it configured for the Degrees/Decimal Minutes format that is standard for GPS.
https://support.google.com/earth/answer/148070?hl=en
Please be positive and constructive with your questions and comments.