readFlatCoordinates(node, objectStack) {
    const s = getAllTextContent(node, false).replace(/^\s*|\s*$/g, '');
    const context = /** @type {import("../xml.js").NodeStackItem} */ (
      objectStack[0]
    );
    const containerSrs = context['srsName'];
    let axisOrientation = 'enu';
    if (containerSrs) {
      const proj = getProjection(containerSrs);
      if (proj) {
        axisOrientation = proj.getAxisOrientation();
      }
    }
    const coordsGroups = s.trim().split(/\s+/);
    const flatCoordinates = [];
    for (let i = 0, ii = coordsGroups.length; i < ii; i++) {
      const coords = coordsGroups[i].split(/,+/);
      const x = parseFloat(coords[0]);
      const y = parseFloat(coords[1]);
      const z = coords.length === 3 ? parseFloat(coords[2]) : 0;
      if (axisOrientation.startsWith('en')) {
        flatCoordinates.push(x, y, z);
      } else {
        flatCoordinates.push(y, x, z);
      }
    }
    return flatCoordinates;
  }
@param {Node} node Node.
@param {Array<*>} objectStack Object stack.
@return {Array<number>|undefined} Flat coordinates.