Vector VRT — vector_vrt • vapour

Just a simple text generator to generate the VRT for a vector layer, First layer is chosen if not otherwise specified.

vector_vrt(x, layer = 1L, projection = NULL, sql = NULL, a_srs = NULL)

Arguments

x: data source name
layer: layer index (1-based) or name
projection: crs of the output
sql: SQL for ExecuteSQL to define the layer
a_srs: set the source crs

Value

single element character vector

Details

Using 'sql' overrides the 'layer', and using 'projection' results in the geometries being transformed. No check is made of the layer source projection.

Use 'a_srs' to ensure the source has a source crs (that might be the only thing you use this for, even if not reprojecting).

It's expected that if you use this with a source without a source projection, you'll get "Failed to import source SRS", so use argument "a_srs" to set it if needed (or many other GDAL other facilities that do this).

Examples

file <- "list_locality_postcode_meander_valley.tab"
## A MapInfo TAB file with polygons
mvfile <- system.file(file.path("extdata/tab", file), package="vapour")
vector_vrt(mvfile, sql = "SELECT * FROM list_locality_postcode_meander_valley LIMIT 5 OFFSET 4")
#> [1] "<OGRVRTDataSource>\n     <OGRVRTLayer name=\"list_locality_postcode_meander_valley\">\n    <SrcDataSource>/home/runner/work/_temp/Library/vapour/extdata/tab/list_locality_postcode_meander_valley.tab</SrcDataSource>\n    <SrcSQL>SELECT * FROM list_locality_postcode_meander_valley LIMIT 5 OFFSET 4</SrcSQL> \n    </OGRVRTLayer>\n </OGRVRTDataSource>"

## read this with vapour_read_geometry() and it will be projected to VicGrid
vector_vrt(mvfile, projection = "EPSG:3111")
#> [1] "<OGRVRTDataSource>\n  <OGRVRTWarpedLayer>\n     <OGRVRTLayer name=\"list_locality_postcode_meander_valley\">\n    <SrcDataSource>/home/runner/work/_temp/Library/vapour/extdata/tab/list_locality_postcode_meander_valley.tab</SrcDataSource>\n    <SrcLayer>list_locality_postcode_meander_valley</SrcLayer> \n    </OGRVRTLayer>\n    <TargetSRS>EPSG:3111</TargetSRS>\n    </OGRVRTWarpedLayer>\n </OGRVRTDataSource>"