基于数字摄影测量的雪盖制图方法探讨

受地形、植被、太阳辐射以及分吹雪等因素影响,山区积雪时空分布差异性很大,人工观测和卫星遥感手段很难获取高时空分辨率的雪盖信息.2010年3—5月在祁连山葫芦沟一级小支流开展了相机摄影试验,并应用摄影测量技术将野外拍摄影像转化为正射积雪空间分布图像,以此获取小流域高时空分辨率的积雪分布信息.结果表明:20次摄影测量后方交会解得到的摄影中心与实测摄影中心误差ΔX分布在-9.27～25.51m之间,而ΔY分布在-33.53～18.2m,ΔZ区于-3.33～9m之间.单张积雪制图误差分析表明,ΔX分布在-9.27～25.51m之间,而ΔY分布在-33.53～18.2m,ΔZ区于-3.33～9m之间,边缘处积雪制图误差大于中心位置.进一步分析表明,高程数据精度、摄影距离和摄影倾角等因素影响数字摄影测量雪盖制图的精度.随着地形数据精度的提高,正射积雪制图的精度有很大的提升空间,相机摄影测量也将成为小流域尺度、坡面尺度雪盖信息获取的有效手段之一.

Mapping Snow Cover Based on Digital Photogrammetry

Spatial and temporal distribution of snow cover is complicated and greatly affected by topography,land cover,radiation and snow drifting.Snow cover information with high spatial and temporal resolution is hard to obtain by in-situ measurements or satellite image.In this paper,a small watershed of Hulugou River was selected as a conventional photography experiment field.It was tried to use photos by using photogrammetry to obtain spatial distribution information of snow cover through orthographic Projection system.It was found that between the measured and the calculated projection centers there was a difference ΔX of-9.27~25.51 m,a difference ΔY of-33.53~18.2 m and a difference ΔZ of-3.33~9 m.Error analysis of single snow cover map shows that the differences in X,Y and Z are-9.27~25.51 m,-33.53~18.2 m and-3.33~9 m,respectively.Further analyses indicate that the precision of snow cover mapping depends on precision of DEM,photographic distance and photographic angle.However,with the improvement of basic topographic data,snow cover map derived from photogrammetry will be advanced.