IGN API elevation line

calculate_elevation_layers_for_selected_lines.py

import json
import tempfile
import urllib.request

baseUrl='https://wxs.ign.fr/calcul/alti/rest/elevationLine.json'

layer = iface.activeLayer()
# Caution: our line is a linestring and use by default epsg 4326, so we already have lon, lat
# You also need to select a line for the layer 
for feature in layer.selectedFeatures():
    lons = '|'.join([str(coord.x()) for coord in feature.geometry().asPolyline()])
    lats = '|'.join([str(coord.y()) for coord in feature.geometry().asPolyline()])
    url = f"{baseUrl}?sampling=500&lon={lons}&lat={lats}"
    response = json.load(urllib.request.urlopen(url))
    geojsonFeatures = []
    for pt in response.get('elevations'):
        geojsonFeatures.append({
            "type": "Feature",
            "properties": {"acc": pt.get('acc'), "z": pt.get('z')},
            "geometry": {
                "type": "Point",
                "coordinates": [
                    pt.get('lon'),
                    pt.get('lat'),
                    pt.get('z')
                ]
            }
        })
    mygeojson = {
        "type": "FeatureCollection",
        "features": geojsonFeatures
    }
    with tempfile.NamedTemporaryFile(mode='w', encoding='utf-8', delete=False, suffix='.geojson') as infile:
        outname = infile.name
        json.dump(mygeojson, infile)
    iface.addVectorLayer(outname, outname, 'ogr')

# Convert to local projection layer to get meters for distance
# Then open in QGIS plugin "Profile tool"