Geodesics算法在雷达投影转换中的应用检验

Application and Verification of Geodesics Algorithm in Radar Projection Conversion

基于上海市气象局布设于临港的X波段移动式双线偏振雷达观测资料,利用反射率因子、差分反射率和相关系数等变量识别出东海大桥固定地物回波位置,进而采用Geodesics和HRAP(Hydrologic Rainfall Analysis Project)投影转换算法将雷达回波的极坐标位置转换至地理坐标。以国家测绘局利用GPS技术测量的沪芦高速(东海大桥段)地理坐标作为真值,将环境大气分为晴空回波-低湿度情况和降水回波-高湿度情况分类检验两种算法的效果。检验算法包含经投影转换后地物回波样本位于桥面主体内部的数目(多边形检验)和样本偏离桥体中心线的距离(中心线检验)。其结果表明:Geodesics算法在多边形和中心线检验方面表现均优于HRAP算法,其在雷达投影转换的实际业务中具备一定的应用价值。

Based on the data observed by the X-band dual-polarization mobile radar located at Lingang owned by the Shanghai Meteorological Service,the fixed ground clutter echo of the East China Sea Bridge can be recognized with reflectivity,differential reflectivity and correlation coefficient.Then the Geodesics and HRAP algorithms are introduced to transform the position of fixed ground clutter echoes from polar coordinate to geographic coordinate.The GPS-measured geographic position of Hulu Highway(East China Sea Bridge section)from the National Geomatics Center of China is regarded as the true value.These two algorithms are examined separately under two types of atmospheric conditions:the clear echo with low humidity and the precipitation echo with high humidity.The verification algorithms include two methods:the number of samples located inside the bridge polygon(polygon verification)and the distance from the bridge centerline(centerline verification).The result shows that the Geodesics algorithm performs better compared with the HRAP algorithm both in polygon verification and centerline verification,indicating its importance in the practical application of radar projection conversion.