A small function to get an altitude profile from Swisstopo based on their API

get_swisstopo_elevation_profile.py

def get_swisstopo_elevation_profile(coords,  # a path (2+ points in the form)
                                    kind='csv',
                                    # three heights are available for JSON
                                    # COMB, DTM2, DTM25
                                    which='COMB',
                                    asnumpy=True,
                                    quiet=True,
                                    opts={"sr": None,
                                          "nb_points": None,
                                          "offset": None,
                                          "distinct_points": True,
                                          "callback": None,
                                          }
                                    ):
    """
    Call the swisstopo API for altitude data along a path.

    Pass in a list or array of coordinates in EPSG 2056 (LV95) or 21781 (LV03)
    to get altitude values along the provided path. For options see keywords or
    parameters of call via swisstopo API.

    Parameters
    ----------
    coords : list or numpy array
        The coordinates in either EPSG 2056 (LV95) or EPSG 21781 (LV03).
    kind : str, optional
        Which API backend should be queried. Available are json and csv.
        If none of these are passed properly, fallback is csv.
        The default is 'csv' (easier structure to parse).
    which: str
        If kind is json, three altitude values are available, DTM2, DTM25 and
        COMB(INATION).
    asnumpy : bool, optional
        Whether to return a numpy array.
        The default is True.
    quiet : bool, optional
        Whether to quiet the output (True) or not.
        The default is True.
     opts: dict
        Further keywords than can be passed to the API call, see
        https://api3.geo.admin.ch/services/sdiservices.html#profile

    Returns
    -------
    list or numpy array
        The returned points, in the form of distance along path, altitude,
        coordinates.

    """

    import requests
    import numpy as np

    if len(coords) > 5000:
        print('Warning, number of coordinates exceeds swisstopo API'
              'max number of points, reduce coords beforehand.')
        return np.asarray([]) if asnumpy else []

    payload = 'geom={"type":"LineString","coordinates":['
    payload += ','.join([f"[{coord[0]},{coord[1]}]"
                         for coord in coords])
    payload += ']'
    opts = ','.join(['"'+str(key)+'"'+':'+'"'+str(opt)+'"'
                     for key, opt in opts.items()
                     if opt is not None])
    if opts:
        payload += ',' + opts
    payload += '}'
    kind = kind.lower()
    if kind.lower() not in ['csv', 'json']:
        if not quiet:
            print('Only csv or json can be chosen, autoselecting csv')
        kind = 'csv'

    baseurl = "https://api3.geo.admin.ch/rest/services/profile." + kind
    try:
        profile = requests.get(baseurl, params=payload)
    except ConnectionError:
        if not quiet:
            print('Connection timeout')
        return np.asarray([]) if asnumpy else []

    if profile.ok:
        if not quiet:
            print('Success')
    else:
        if not quiet:
            print('Failed')

    if kind == 'csv':

        profile = profile.text.split('\r\n')
        # Distance, Altitude, Easting, Northing -> not needed
        # header = profile[0]
        profile = list(map(lambda x: [float(j.strip('"'))
                                      for j in x.split(';')],
                           profile[1:-1]))
    elif kind == 'json':

        profile = [[p['dist'], p['alts'][which],
                    p['easting'], p['northing']]
                   for p in profile.json()]

    if asnumpy:
        profile = np.asarray(profile)

    return profile


if __name__ == '__main__':
    # straightforward example usage
    rw=[2611025.0, 2620975.0, 2633725.0]
    hw=[1266400.0, 1256750.0, 1250000.0]
    profile = get_swisstopo_elevation_profile(list(zip(rw, hw)))
    import matplotlib.pyplot as plt
    plt.fill_between(profile[:,0], 
                     profile[:,1], 
                     facecolor='grey',
                     edgecolor='k',
                     alpha=0.8)
    plt.ylim(min(profile[:,1]), None)