public function readDemPackage($pathToDemFile, $pathToDemNode)
    {
        $json = file_get_contents($pathToDemFile);
        $data = json_decode($json, true);
        $paths = explode(self::PS, $pathToDemNode);
        foreach ($paths as $path) {
            if (strlen(trim($path)) > 0) {
                if (isset($data[$path])) {
                    $data = $data[$path];
                } else {
                    throw new \Exception("Cannot find DEM node '$pathToDemNode' in file '$pathToDemFile'.");
                }
            }
        }
        $result = new Data($data);
        return $result;
    }