A study of altimeter height control in a gravity survey around Kuala Pilah, central Malaysia

The survey was undertaken to determine the reliability of pressure-sensitive altimeters for surveys in Malaysia of areas with sparse elevation control (much of the country). It is shown that with 3 or 4 repeat measurements and with control measurements at no more than hourly intervals, that relative elevations can be determined to approximately metre accuracy with a resulting Bouguer gravity uncertainty of 0.2 milligals. It is suggested that for general applications altimeter controlled surveys are sufficient for delineating anomalies greater than 5 milligals. A previous single gravity traverse had established a Bouguer gravity variation of over 30 milligals in the Kuala Pilah area where there are both a major granite contact and a proposed crustal suture. By extending the gravity coverage to unsurveyed areas it was possible to test if there was any separate evidence for the suture from a map of gravitational variation. The survey results show that the Bouguer gravity contours parallel the granite contact and do not support any other sharp density variations within tile area mapped (although either gradual or deep variations would not be recognised on this local scale). Considerable lateral variation between profiles across the granite contact were mapped and simple 2- dimensional models are presented for these profiles