What could go wrong when merging multiple GeoJSONs?

Question

Attempt I - ogrmerge

I have a few GeoJSONs in a directory called jordsmonnfiles. I want to get one GeoJSON file with the features from the files matching the pattern jordsmonnfiles/jordsmonn_*JK1.geojson. My first attempt:

python3 ogrmerge.py -f GeoJSON -o JK1.geojson -nln JK1 jordsmonnfiles/jordsmonn_*JK1.geojson

I get the error:

ERROR 1: Layer JK1 already exists, and -append not specified. Consider using -append, or -overwrite. ERROR 1: Terminating translation prematurely after failed translation of layer JK1 (use -skipfailures to skip errors)

I read up on the -append flag in the documentation, which describes it as:

Open an existing dataset in update mode, and if output layers already exist, append the content of input layers to them.

Trying it:

python3 ogrmerge.py -f GeoJSON -o JK1.geojson -nln JK1 jordsmonnfiles/jordsmonn_*JK1.geojson -append

Output:

ERROR: -f incompatible with -update

Take away the -f flag then:

python3 ogrmerge.py -o JK1.geojson -nln JK1 jordsmonnfiles/jordsmonn_*JK1.geojson -append

ERROR: Destination dataset does not exist

How could I unite all the defined geometries in files matching the pattern jordsmonnfiles/jordsmonn_*JK1.geojson into a single file?

The schematic view of the desired output would be:

{
"type": "FeatureCollection",
"name": "WHATEVER_NAME",
"features": [
    { "type": "Feature",
      "properties": "WHATEVER, I DON'T NEED TO PRESERVE PROPERTIES OF SOURCE FILES",
      "geometry":
        { "type": "Polygon",
        "coordinates": [[[10.0,11.2], [10.5, 11.9],[10.8, 12.0],[10.0,11.2]]] }
    },
    { "type": "Feature",
      "properties": "WHATEVER, I DON'T NEED TO PRESERVE PROPERTIES OF SOURCE FILES",
      "geometry":
        { "type": "Polygon",
        "coordinates": [[[12.0,14.2], [12.5, 14.9],[12.8, 14.0],[12.0,14.2]]] }
    },
]
}

I only care about geometries, not properties of each. I don't want to unite them in the sense of producing a MultiPolygon, but I want to list all of the geometries separately in the features part of the GeoJSON.

---

Attempt II - mapbox/geojson-merge

I have also tried to use geojson-merge.

npm install -g @mapbox/geojson-merge # installs successfully
geojson-merge jordsmonnfiles/jordsmonn_*JK1.geojson > JK1.geojson 

Output:

/opt/homebrew/lib/node_modules/@mapbox/geojson-merge/geojson-merge:17 process.stdout.write(JSON.stringify(merge(argv._.map(function(n) { ^

RangeError: Invalid string length at JSON.stringify () at Object. (/opt/homebrew/lib/node_modules/@mapbox/geojson-merge/geojson-merge:17:29) at Module._compile (node:internal/modules/cjs/loader:1105:14) at Module._extensions..js (node:internal/modules/cjs/loader:1159:10) at Module.load (node:internal/modules/cjs/loader:981:32) at Module._load (node:internal/modules/cjs/loader:827:12) at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12) at node:internal/main/run_main_module:17:47

Node.js v18.0.0

Answer 1

You did not find one option when reading https://gdal.org/programs/ogrmerge.html

-single If specified, all input vector layers will be merged into a single one.

Then do:

 ogrmerge -single -o merged.json *.json

How to merge just geometries but not attributes is worth another question. I do not believe it is possible with ogrmerge.