Matching photos to features

When somebody takes a photo on a feature in a cloud project, the app names the file after the feature and after the photo itself, so no two phones in your organisation can ever make the same name. The next sync sends the photo’s details: its name, size, checksum, type, when it was taken, and which feature it belongs to. The file itself stays on that phone.

Everybody else in the project sees that the feature has a photo on another phone, but not the photo. The attachment list below says whose phone.

On each phone the attachments of a cloud project are in the Mapit GIS folder, under Mapit-Data, Attachments, then the project’s name. Ask each person to copy that project folder to wherever you collect work: a cable, a file manager, a shared drive. Put the folders from several phones into one folder on your computer: they merge without a clash, because every file name is unique.

Each phone also keeps a list in that folder, attachments.csv, naming every photo with its checksum, and saying whether the file is on that phone.

On the cloud project’s page, Download attachment list gives you one line per photo or video in the project: its layer, the feature it belongs to, the file name, its checksum and size, when it was taken, who took it and on which phone. Admins and managers can download it.

Match a file by its name. If a file was renamed on the way, match it by its checksum (SHA-256): the same checksum proves it is the same file, whatever it is called now.

Export the project as a GeoPackage, and open the attachment list as a table. Every layer has a column called uuid, and the list has feature_uuid: add a relation between the two, and each feature shows its photos. Set the list’s file name field to show as an attachment, with the folder you collected the files into, and QGIS shows the photo itself.

Mapit Cloud does not store, back up or show your photos. If a phone is lost before its folder was copied, its photos are lost with it; the list still says which ones existed. Photos taken before a phone had this version of the app get their name and checksum on that phone’s next sync, from the files it holds.