Satellite mapping in cities: how good can it get?

Society needs better maps of its ever-more congested cities – particularly for buried utilities, the locations of which are approximate at best. One of the most convenient surveying methods is to use global satellite-navigation systems, but ‘urban canyons’ are not ideal for satellite reception. This paper looks at the current and future status of the world's global navigation satellite system (GNSS) constellations and the advantages they offer for positioning surveys. Tests using a satellite-navigation system simulator show that a large proportion of urban areas are indeed difficult to position to centimetre level using a single satellite constellation alone, but this could improve significantly with the addition of further constellations in the near future.