Test: World Accuracy of Snapbridge GPS

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simpsondb New Member • Posts: 14
Test: World Accuracy of Snapbridge GPS
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I have been following a post where the OP is seeking advice for an accurate GPS unit to work with the Z specifically for Altitude information, https://www.dpreview.com/forums/thread/4409521 .

I was curious as to the general accuracy of using a SmartPhone with SnapBridge so I did some tests of pictures taken both in the US and Italy. Predictably, the results varied significantly.

The base case was using my mailbox as a known coordinate. Then I took three shots beside the mailbox at SnapBridge Low, Medium and High accuracy with an iPhone 5s. The results are in the chart below.

A more expansive test was using previously taken photos using SnapBridge on an iPhone 7 in Italy, 1) at the center of the Coliseum, 2) at the Tivoli Fountain, and 3) at the top of Mt. Vesuvius crater. I used Google maps to get baseline coordinates at these locations where I knew I was standing. I then used EXIFTools to extract the GPS data from the JPEG files. I used an Excel VB module to calculate the distance deltas. The results are also shown below.

Summary:

⁃ The accuracy of the GPS data derived from your SmartPhone can be very inaccurate based on location.
⁃ The accuracy next to my mailbox ranged from 4 to 80 feet with SnapBridge High the most inaccurate using an iPhone 5s.
⁃ In Italy, the Coliseum was off by 600 feet, Tivoli fountain off by 67 feet, Mt. Vesuvius was off by 3.3 KM using an iPhone 7.
⁃ However, Altitude was only off by 2 to 5 meters with the exception of Mt. Vesuvius which was off by only 30 meters.
⁃ I could not test the accuracy of the iPhone 5s versus the iPhone 7 at the same locations.
⁃ I would be very interested in others experience using newer iPhones and Android devices.

Bottom line:

⁃ The SnapBridge GPS gets you in the neighborhood for minimal cost (with the exception of the top of a volcano and the like).
⁃ If you need dependable, accurate GPS EXIF data, a dedicated GPS unit may be the answer.

Regards

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