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How to set spatial reference system in readogr?
It will set the spatial reference system if the layer has such metadata. If reading a shapefile, the data source name ( dsn= argument) is the folder (directory) where the shapefile is, and the layer is the name of the shapefile (without the .shp extension).
How are OGR fields read in rgdal 0.5?
From rgdal 0.5-27, missing value handling has been improved, and OGR unset field values are set to NA in R, but drivers and external files may vary in their representations of missing values. In addition, from 0.6-9 date and time fields are read as strings rather than being treated as unsupported; NULL geometries are identified and dropped.
Can a vector object be read from an OGR layer?
The function reads an OGR data source and layer into a suitable Spatial vector object. It can only handle layers with conformable geometry features (not mixtures of points, lines, or polygons in a single layer).
How are null geometries reported in ogrinfo and readogr?
There are differences in the reporting of NULL geometries between ogrInfo and readOGR – in ogrInfo, only declared NULL geometries are reported, but in readOGR, any line or polygon geometries with no coordinates are assigned NULL geometry status as well. An attempt is made to close unclosed rings in polygon geometries.
How are coordinate reference systems ( CRS ) used in the US?
CRS provide a standardized way of describing locations. Many different CRS are used to describe geographic data. The CRS that is chosen depends on when the data was collected, the geographic extent of the data, the purpose of the data, etc. EPSG codes for commonly used CRS (in the U.S.)
How to read OGR vector maps into spatial objects?
The drivers available will depend on the installation of GDAL/OGR, and can vary; the ogrDrivers () function shows which are available, and which may be written (but all are assumed to be readable). Note that stray files in data source directories (such as *.dbf) may lead to suprious errors that accompanying *.shp are missing.