I'm trying to use mapshaper.org to convert some geojson files to topojson, and I need the identifying properties to be preserved.
Normally this would be done with the
-p flag on the command line, but despite mapshaper having the facility to allow "options from the command line interface", I can't get it to work.
-p identifier-name which give the error:
Unknown command: p
...and I've tried I've tried
"-p identifier-name" in quotes following the help examples which give the error:
Unknown output option: -p identifier-name
Update: I've figured out that Mapshaper isn't passing these commands to the normal
topojson tool, it's using them in its own custom command line interface, which is documented here (strangely there don't seem to be any links to this in Mapshaper itself).
In theory I want the option
"id-field=nameoffield" but it doesn't seem to make any difference - all the geojson properties are still appended to the end of the file and the named property is not changed to an identifier.
How can I filter the properties in Mapshaper like I would with the command
topojson in.json -o out.json -p prop1,prop2?