GSWA Gascoyne Elevation Line Data

Digital Elevation Model data record the terrain height variations from the processed point-located data recorded on an airborne geophysical survey.� The aircraft altimeter data records the height of the aircraft above the ground and the aircraft GPS records the height of the aircraft above the ellipsoid.� Subtracting the two values enables the height of the terrain beneath the aircraft relative to the ellipsoid to be calculated.� This ellipsoidal terrain height is corrected for the variation between the ellipsoid and the geoid (the n-value correction) to produce terrain heights relative to sea level.

数字高程模型（Digital Elevation Model）数据记录了由航空地球物理勘探采集的经处理点位观测数据反演得到的地形高程变化。机载高度计数据可记录飞行器距地面的高度，机载GPS则能获取飞行器相对于参考椭球体的高度。将两组高度数值相减，即可计算出飞行器下方地形相对于参考椭球体的高程。随后需对该椭球面地形高程进行参考椭球体与大地水准面之间的偏差改正（即n值改正），最终得到相对于海平面的地形高程。