QGIS Algorithm provided by GRASS r.drain (grass:r.drain). Traces a flow through an elevation model on a raster map.

grass_r_drain(
  input = qgisprocess:::qgis_default_value(),
  direction = qgisprocess:::qgis_default_value(),
  start_coordinates = qgisprocess:::qgis_default_value(),
  start_points = qgisprocess:::qgis_default_value(),
  .c = qgisprocess:::qgis_default_value(),
  .a = qgisprocess:::qgis_default_value(),
  .n = qgisprocess:::qgis_default_value(),
  .d = qgisprocess:::qgis_default_value(),
  output = qgisprocess:::qgis_default_value(),
  drain = qgisprocess:::qgis_default_value(),
  GRASS_REGION_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_REGION_CELLSIZE_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_RASTER_FORMAT_OPT = qgisprocess:::qgis_default_value(),
  GRASS_RASTER_FORMAT_META = qgisprocess:::qgis_default_value(),
  GRASS_SNAP_TOLERANCE_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_MIN_AREA_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_OUTPUT_TYPE_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_VECTOR_DSCO = qgisprocess:::qgis_default_value(),
  GRASS_VECTOR_LCO = qgisprocess:::qgis_default_value(),
  GRASS_VECTOR_EXPORT_NOCAT = qgisprocess:::qgis_default_value(),
  ...,
  .complete_output = .complete_output_option(),
  .quiet = .quiet_option(),
  .messages = .message_option()
)

Arguments

input

raster - Elevation. Path to a raster layer.

direction

raster - Name of input movement direction map associated with the cost surface. Path to a raster layer.

start_coordinates

point - Map coordinates of starting point(s) (E,N). Point coordinate as an 'x,y' string, e.g. '1.5,10.1'.

start_points

source - Vector layer containing starting point(s). Path to a vector layer.

.c

boolean - Copy input cell values on output. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -c.

.a

boolean - Accumulate input values along the path. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -a.

.n

boolean - Count cell numbers along the path. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -n.

.d

boolean - The input raster map is a cost surface (direction surface must also be specified). 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -d.

output

rasterDestination - Least cost path. Path for new raster layer.

drain

vectorDestination - Drain. Path for new vector layer.

GRASS_REGION_PARAMETER

extent - GRASS GIS region extent. A comma delimited string of x min, x max, y min, y max. E.g. '4,10,101,105'. Path to a layer. The extent of the layer is used..

GRASS_REGION_CELLSIZE_PARAMETER

number - GRASS GIS region cellsize (leave 0 for default). A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_RASTER_FORMAT_OPT

string - Output Rasters format options (createopt). String value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_RASTER_FORMAT_META

string - Output Rasters format metadata options (metaopt). String value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_SNAP_TOLERANCE_PARAMETER

number - v.in.ogr snap tolerance (-1 = no snap). A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_MIN_AREA_PARAMETER

number - v.in.ogr min area. A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_OUTPUT_TYPE_PARAMETER

enum of ("auto", "point", "line", "area") - v.out.ogr output type. Number of selected option, e.g. '1'. Comma separated list of options, e.g. '1,3'.

GRASS_VECTOR_DSCO

string - v.out.ogr output data source options (dsco). String value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_VECTOR_LCO

string - v.out.ogr output layer options (lco). String value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_VECTOR_EXPORT_NOCAT

boolean - Also export features without category (not labeled). Otherwise only features with category are exported. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

...

further parameters passed to qgisprocess::qgis_run_algorithm()

.complete_output

logical specifying if complete out of qgisprocess::qgis_run_algorithm() should be used (TRUE) or first output (most likely the main) should read (FALSE). Default value is TRUE.

.quiet

logical specifying if parameter .quiet for qgisprocess::qgis_run_algorithm() Default value is TRUE.

.messages

logical specifying if messages from qgisprocess::qgis_run_algorithm() should be printed (TRUE) or not (FALSE). Default value is FALSE.

Details

Outputs description

  • drain - outputVector - Drain

  • output - outputRaster - Least cost path