$area在计算面积的时候会先看当前项目的椭球的设置,如果设置了椭球,那么计算出来的面积就是椭球面积,如果没有设置椭球,那么计算出来的面积就是平面面积。 椭球设置方法如下:依次打开 工程 -- 工程属性 选择常规选项卡 area 函数 详细写法 area($geometry) 官网解释: Returns the area of a geometry polygon object...
请注意,虽然QGIS允许您更改工程/图层的CRS,但这样做是不够的,因为它不会保存数据,只会为用户重新投影视图。 参考:GitHub - jonnyhuck/RFCL-PolygonDivider:用于分割多边形的QGIS插件
“If the zone input is a feature dataset, a vector-to-raster conversion will be internally applied to it”。 当单个要素的面积小于或者接近于栅格的cell时,可能会不展示出来。“If the areas of single features are similar to or smaller than the area of single cells in the value raster, in the...
By the end of this practical you will have developed experience in: Handling and adding point and polygon (vector) data to a GIS; Reprojecting a layer to another coordinate reference system (CRS); Creating table joins; Spatial analysis: interpolation of air quality data (NO2) (raster); Usin...
3. Calculating the Area of Polygons A script to calculate the area of each feature in a polygon layer and add this as a new attribute. ##Calculate_Area=name ##Input_layer=vector ##Area_field_name=string area from qgis.core import QgsField, QgsExpression, QgsExpressionContext, QgsExpressionCo...
My first thought for a workaround is just create a zero area polygon for the centerline. That is LL=UL and LR=UR. But since I do not really need the ridgeline as a geometry with duplicate attributes, I wonder if I can add a symbol to the polygon layer that represents the ridgeline....
Catchment Area You can check the log messages to find more information about the execution of the algorithm Several SAGA algorithms yield the same error, while others work well apparently such as "clip raster with a polygon". I have been looking in the internet for potential solutions and I ...
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It creates a new vector layer in which polygons with holes have been replaced by polygons with only their external ring. Attributes are not modified. I left the optional minimum area parameter default 0.0; that resulted: ...in all holes being removed. Here's the link to: QGIS manual. ...
“Clip trajectories by extent”still exists but, additionally, we can now also“Clip trajectories by polygon layer” There are two new event extraction algorithms to“Extract OD points”and“Extract OD points”, as well as the related“Split trajectories at stops”. Additionally, we can also“Sp...