高精度航空重力测量空间改正优化方法研究

Research on optimization of free-air correction for high-precision airborne gravimetry

航空重力测量精度逐步提高,达到1 mGal或更好,另外在高海拔地区、大范围区域纬度跨度很大,均要求空间改正项更精确.目前空间改正方法不完备,针对此问题,给出了重力扰动一步归算法-球谐系数法,用Somigliana公式对其正确性进行了验证,并以球谐系数法为参考,对比分析了不同空间改正公式对重力扰动归算的影响.结果表明,美国大地测量局(NGS)改进的三阶公式精度最高,H&M(Heiskanen和Moritz,1967)二阶公式次之,我国学者广为采用的二阶公式精度较低.因此,在1 mGal或更好精度的航空重力测量,或者高海拔测量,建议采用球谐系数法或NGS改进的三阶公式进行归算,以提高航空重力测量成果精度.

Airborne gravimetry accuracy gradually increase to 1 mGal or better,while in high altitude,large-scale regional latitude span,require free-air correction more accurate.At present,the free-air corrections is incomplete.Based on this fact,we propose spherical harmonic coefficient method,which is a one-step reduction method of gravity disturbance,and its correctness is verified by the Somigliana formula.Then analyze the influence of different free-air correction formulas on gravity disturbance reduction with the reference of spherical harmonic coefficient method.The results show that NGS-improved third order free-air correction has the highest accuracy,H&M free-air correction takes the second place,and the second-order formula widely adopted by Chinese scholars has lower accuracy.Therefore,we recommend to use the spherical harmonic coefficient method or the NGS-improved thirdorder formula to improve the accuracy of airborne gravimetry when at 1 mGal or better accuracy of airborne gravimetry or high-altitude surveying.