Author Topic: Geolocation Support for GCJ-02 - Making photos taken in China line up properly  (Read 242 times)

Offline DanY

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Hi CameraBits. I'm a new user of Photo Mechanic Plus and love the software for its "database" and metadata features. My registered email with the software is yongkk@gmail.com

I have a feature request and pardon me if I don't exactly describe the steps concerning adding GNSS a.k.a GPS coordinates as I'm new to the software. But I think you'll get my idea.

I love to travel and take photos and like most people who use metadata, like to have the coordinates associated with the photo be it raw or jpeg. While I only started using PhotoMechanicPlus during the pandemic and hence haven't been travelling, I'm told that when in one of my favourite destinations China, the GPS coordinates provided by the likes of google maps are off by several city blocks. This is because China uses the GCJ-02 datum, not the WGS-84 datum. I'm guessing that importing the GPS coordinates into photomechanic uncorrected will result in inaccurate positioning. This "GPS shift" problem and the solution is described here https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#GCJ-02

It seems there are "several open-source projects exist that provide conversions between GCJ-02 and WGS-84, for languages including C#, C, Go, Java, JavaScript, PHP Python, R, and Ruby. The solution is also provided via "reverse transformation". (Source is the wikipedia link above).

Here is how I envision the feature to work in PMP. After the coordinates for a photo are read by PMP, have a drop down box which allows the coordinates for that photo to be shown in "China / GCJ-02 datum" or keep to WGS-84 datum. Also have a feature for bulk selection of photos to show either "positioning transformation". This should reflect correctly on a map. I'm told that things work properly for popular software Gaia GPS and OpenStreetMaps. So its certainly something that other software have already adapted to. (Source: https://blog.gaiagps.com/gaia-gps-chinas-gps-restrictions/)

Remember China is a big market with the likes of Adobe's Creative Suite and BlackMagic's Davinci Resolve already servicing the China market. So it's something certainly useful for more users going forward.

Hope you can build this as a feature for the next update! Hope to hear from you soon. Thanks.

Regards,
DY
PMP user