GPS data format inaccurate

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  • Updated 3 years ago
Merged

This conversation has been merged. Please reference the main conversation: Lightroom: Display GPS coordinates with more precision

Bottom line
1. LR takes the GPS data (residing in the image's metadata) & (at least in the case of Nikon-derived data) changes the format of that GPS data; and,
2. Much to my annoyance, as part of the data-format conversion, LR renders that Nikon-derived GPS data with less precision.

Background
I spend half of my time in a New Hampshire lakeside community (EastmanNH.org) which is very protective of its lake, lest invasive vegetation turn it into a swamp. Among multiple relevant initiatives, we do a decennial lake survey: A team inspects the shoreline from a boat, collecting vegetation specimens, making observations, photographing, & recording clock time & GPS coordinates.

I was the photographer in the team this summer: I used a Nikon D810 with Nikon's GPS accessory (GP-1). Here is typical set of GPS coordinates visible on the camera's screen:
N 43 30.954; W 72 06.862.
However, once that image is imported into LR, its GPS data (as viewed in LR's metadata panel) has undergone a seemingly unimportant format conversion:
N 43 deg 30'57"; W 72 deg 06'52".
Most photographers will not care about this data conversion, since they are likely interested only in the mapping application. Also, their capture sites are probably much more dispersed.

Why do I care? Our lake-survey project involves hundreds of images captured from locations that are not terribly far from each other. When I perused the images in LR, it became apparent that a fair number of lake locations had the same GPS coordinates. However, when I put the memory cards back into the camera, to read the GPS coordinates, it was clear that, among images with the same GPS coordinates in LR, there were differences in the third decimal point. As a result, fewer images had the same GPS coordinates when data were review in the camera.

Thus, coincident with the LR-derived GPS data-format conversion, the GPS data loses precision, at least in terms of data values that are displayed. Although it is quite likely that if LR displayed the 'second' value with a decimal (e.g., 30'57.2), the same precision in the location would exist; however, the typical LR user cannot view or benefit from that greater precision. (BTW: Many handheld GPS devices display GPS data in the same, higher-precision format as my Nikon camera.)
Photo of Fredrick Orkin

Fredrick Orkin

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Posted 3 years ago

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Bob Trlin

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Nikon displays its data to the third decimal place of a minute of arc.  At a latitude of 45° that amounts to about 1.8m.  However, civilian GPS units can claim an accuracy of no more than 7.8m with a 95% confidence interval.  My person observation is that they are good for only about 10m in practical terms despite the advertising hype.  Nevertheless, it doesn't help if LR then rounds off to the nearest second which amounts about 30m.  This then amounts to a total accuracy of about 40m.  I sometimes photograph endangered plants.  It makes it damn hard to find an inconspicuous little plant in the bush if one knows its location to within no better that 10m let alone 40m.  So, despite not using Nikon, I support the above post.

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