GSWA Merredin Bruce Rock 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）数据基于航空地球物理勘探中经处理的点位定位数据，记录地形高程的起伏变化。飞行器高度计数据可记录飞行器距地面的高度，而机载全球定位系统（Global Positioning System，GPS）则可获取飞行器相对于参考椭球体的高度。将两组数值做差，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，针对参考椭球体与大地水准面之间的偏差（即n值改正）对该椭球面地形高程进行校正，最终得到以海平面为基准的地形高程数据。