Accuracy of readings of the Ultimate GPS Logger Shield

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marcelops
 
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Accuracy of readings of the Ultimate GPS Logger Shield

Post by marcelops »

Hello All,

I have been trying the Ultimate GPS Logger Shield (https://www.adafruit.com/products/1272), but I'm experiencing some issues.

To make it simple to explain, I will just use the example included in the Arduino IDE (File / Examples / Adafruit GPS Library / shield_sdlog).

The problem is that I am getting a path that is not very smooth.

For example, I logged a path using both the Arduino and an iPhone. (I just walked around with both devices on). The results are shown in the picture (Arduino in Blue, iPhone in Red:
GPS.png
GPS.png (914.55 KiB) Viewed 333 times
I tried my best to "walk in a straight line", and the GPS log from the iPhone seems to get a better path, while the Arduino seems to be skipping some points, making the path with many sharp turns.

Is there a way to improve these readings?

Thanks!
Marcelo

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adafruit_support_rick
 
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Re: Accuracy of readings of the Ultimate GPS Logger Shield

Post by adafruit_support_rick »

I think the iPhone is simply smoothing the readings. You're looking at an average.

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marcelops
 
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Re: Accuracy of readings of the Ultimate GPS Logger Shield

Post by marcelops »

Thanks for replying!!

Do you have a suggestion of a library, or software, or something I could use to average my readings and make it more "linear", or smooth.

All I want is to avoid this zigzag motion, as I am making some animation with the tracks I am logging.

Also, "snapping to the streets" won't work for me, as my reads will be in open fields (besides my screenshot was taken in the city).

Thanks again

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adafruit_support_bill
 
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Re: Accuracy of readings of the Ultimate GPS Logger Shield

Post by adafruit_support_bill »

GPS in a city environment is subject to multiplath reflections from buildings, so it can be a bit irregular. You may find that your readings in an open field are a little cleaner than what you get in Charlestown. The iPhone is also combining GPS readings with cell-tower signal strengh triangulation to further refine the signal.

There are a number of algorithms used for 'smoothing' GPS generated paths. If you search for "GPS Path Smoothing" you will get lots of hits. Here are a few:

http://commuteatlanta.ce.gatech.edu/Res ... 6-2907.pdf
http://www.geocomputation.org/2007/1B-A ... e1/1B2.pdf
http://www.gpsvisualizer.com/tutorials/ ... lters.html

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