基于MapGIS的极值无偏地球化学等值线图生成方法

在MapGIS中自动生成地球化学等值线时,用三角剖分方法能最大程度地保留原始信息,但其图面可视化效果差,后期修改整饰的工作量巨大。用Gird网格化数据生成等值线,又会出现元素浓集中心和极值点位置存在一定程度的偏差和位移的情况,对后期的地球化学特征分析和异常查证工作带来了不便。经过研究发现,把离散采样点分析数据中的极值点提取出来,按照一定的阀值给极值点建立缓冲区,通过点对区空间分析,把规则网格数据中位置距离极值点较近,可能影响到三角剖分网优化效果的畸形网格节点剔除;再把离散的极值点数据和剔除了畸形网格节点的规则网格数据合并,进行三角剖分等值线追踪,很好地弥补了三角剖分生成等值线可视化效果差和网格化数据生成等值线出现浓集中心偏移的不足。该方法无需借助其他软件工具,在MapGIS中即可实现极值无偏移的地球化学等值线生成,既兼顾了制图精度,又满足了可视化效果,有很强的实用性。

A tentative discussion on the method for generating the extreme value of non-partial geochemical contour map based on MapGIS

The triangular subdivision method can maximally retain the original information when generating geochemical contour in the MapGIS automatically, but its surface visual effect is poor and huge finishing workload will be changed later. When Gird generates isoline grid data, there will be a condition that the accumulation centers of elements and the point location of extreme value will change to some extent, and it is not convenient for analysis of the geochemical characteristics and the anomaly verification work in late stage. Based on studies, the author found that if the extremum points in the discrete sampling point analysis data are extracted, buffer is established for the extremum value points according to a certain threshold, through point?to?area spatial analysis, the deformed grid nodes in the regular grid which are relatively close to the extremum points and might affect the triangle subdivision mesh optimization are rejected. After that, the discrete extreme value point data and the regular grid data that have rejected the deformed grid nodes grid data are merged, followed by triangular subdivision contour tracking. These measures satisfactorily make up the shortcomings of the two methods mentioned above. This method does not need using other software tools and only employs the MapGIS. The method can generate geochemical contour of ex?treme values without deviation, and both the mapping accuracy and the visual effect are fairly good, thus having good practicability.