The airport should publish a 'Radar Minimum Altitude Chart' which shows radar controllers the lowest altitude they can descend traffic to and provide radar vectors. It is drawn so that the minimum clearance of 1000ft above terrain is maintained until the aircraft commences final approach. In the UK, the 'standard' chart is an oval shape 8 nm from either edge of the runway and 13nm from the runway thresholds, but this can vary according to adjacent airfields and the number of runways available. Outside the boundary of the oval, MSA (Minimum Sector Altitude) applies.