GPS Formatting

[RyRy_nz]

Hi I've been using Exif tool to get the full GPS capabilities from my Mavic Air, thankyou. This has helped my thesis greatly.

I did run into a problem though when trying to use a newer version that the 11.08 that i was using and that is the format goes to Degree Min and Second and rounds up to 2 decimals, hence loosing a few meters in accuracy. See example below:

ExifTool Version Number         : 11.08  // The version i used which worked

GPS Latitude Ref                : South
GPS Latitude                    : 34 deg 4' 22.72"
GPS Longitude Ref               : East
GPS Longitude                   : 18 deg 41' 25.96"

Latitude                        : -34.0729901
Longitude                       : +18.6905501

GPS Latitude                    : 34 deg 4' 22.72" S
GPS Longitude                   : 18 deg 41' 25.96" E
GPS Position                    : 34 deg 4' 22.72" S, 18 deg 41' 25.96" E


ExifTool Version Number         : 11.45   // More recent version which is rounded to two decimals

GPS Latitude Ref                : South
GPS Latitude                    : 34 deg 4' 22.72"
GPS Longitude Ref               : East
GPS Longitude                   : 18 deg 41' 25.96"

Latitude                        : 34 deg 4' 22.76" S
Longitude                       : 18 deg 41' 25.98" E

GPS Latitude                    : 34 deg 4' 22.72" S
GPS Longitude                   : 18 deg 41' 25.96" E
GPS Position                    : 34 deg 4' 22.72" S, 18 deg 41' 25.96" E

I cant see why this happened but it seems like functionality was lost.

Thanks Again

[StarGeek]

Have you looked into using either the -n (printConv) option to get the full raw values or using the -c (coordFormat) option to format the values to your preference?

[RyRy_nz]

Wow,

mind blown.

The raw file contains degrees to 15 decimals. Big step up.

Thankyou

[RyRy_nz]

Oh Boy,

Now i'm getting an even more confusing result. Different sets of tags are giving me different locations that are about 1.5m apart from each other.

Latitude                        : -34.0729890
Longitude                       : +18.6905519

GPS Latitude                    : -34.0729768486389
GPS Longitude                   : 18.6905452172472

Id like to trust the first set as that is a more reasonable amount of decimal places but i'm unsure where the rest of the values come from and why there is such a difference.

Possibly from converting ##° #' ##.##" back to decimal °?

Not Ideal.

[Hayo Baan]

It's not unlikely to have slightly different values. GPS coordinates are (usually) recorded as rational numbers (i.e. x/y for integer values x and y). Different base values (y) are used for different fields and software that writes them. Heck, if you edit an image and save it again, chances are that values have changed from the original.

This really isn't a big issue since the differences are (should be) way smaller than the precision of the GPS location anyway.

[RyRy_nz]

Thanks

Yea the error is not insignificant at 1.5m.

But i'm pretty certain that value is calculated from the format with seconds to two decimal places. It seems like DJI has "handicapped" the Mavic Air by forcing some GPS data to have that format while the Latitude and Longitude tag buried deep in the EXIF file which is accurate to about 10cm and has been thankfully extracted with EXIF tool.

[Phil Harvey]

You can see the raw values using the -v option.  This will show the rationals used to store the GPS lat/lon.

- Phil