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Author Topic: Issue reading PPK updated exif coordinate information  (Read 2101 times)

ianSW

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Issue reading PPK updated exif coordinate information
« on: July 22, 2020, 07:22:47 AM »
Recently I have noticed Metashape reading the raw or field GPS coordinate information from DJI Phantom 4 RTK exif data. I have performed PPK processing and written corrected coordinates to the images. Viewing exif data in Geosetter does show both sets of coordinate information but this was not a problem in previous builds. Is there a way to force Metashape to read the corrected GPS positions?

geomaticist

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Re: Issue reading PPK updated exif coordinate information
« Reply #1 on: November 21, 2020, 06:19:43 AM »
ever resolve this? I seem to have the same or similar problem. I re-write the exif position info and metashape is not reading that?

Alexey Pasumansky

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Re: Issue reading PPK updated exif coordinate information
« Reply #2 on: November 21, 2020, 01:39:23 PM »
Hello all,

Please send the original image and image with the modified EXIF to support@agisoft.com, so that we could check, why new values are not read correctly. Also please specify, which tool/command you are using to input new EXIF coordinate values?

Maybe they are written to different IDF table.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Alexey Pasumansky

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Re: Issue reading PPK updated exif coordinate information
« Reply #3 on: November 23, 2020, 02:20:48 PM »
Hello geomaticist,

Thank you for sending the sample files.

For DJI camera data Metashape is using values from the following tags: drone-dji:GpsLatitude and drone-dji:GpsLongitude. If drone-dji:GpsLongitude tag is missing, but drone-dji:GpsLongtitude is present, the latter is used instead. It has been done to allow the compatibility with the old DJI firmware which used the tag name with the typo.

Tags  drone-dji:Latitude and drone-dji:Longitude are not used in the actual Metashape Pro version and we haven't met them, as far as I remember, for DJI images. Also they seem to be missing in DJI specification:
https://dl.djicdn.com/downloads/p4-multispectral/20200717/P4_Multispectral_Image_Processing_Guide_EN.pdf

So it seems that your PPK utility is saving adjusted coordinates to unsupported tags: drone-dji:Latitude and drone-dji:Longitude, and at the same time updates the values in drone-dji:GpsLatitude и drone-dji:GpsLongitude tags. Therefore Metashape reads proper new value from drone-dji:GpsLatitude, but doesn't update the Longitude value, as the old value is read from drone-dji:GpsLongtitude.

At the moment I see the following ways of resolving the issue:
- copying  drone-dji:Longitude value to drone-dji:GpsLongtitude field after PPK processing is completed and image meta data is updated,
- modify the drone-dji:GpsLongtitude field name to drone-dji:Longitude before applying PPK processing,
- modify the PPK tool behavior in order to update the Longitude values in both tags: drone-dji:Longitude и drone-dji:GpsLongtitude.
Best regards,
Alexey Pasumansky,
Agisoft LLC