rsaga.parallel.processing: Parallel Processing

In RSAGA: SAGA Geoprocessing and Terrain Analysis

Parallel Processing

Description

Calculate the size of the local catchment area (contributing area), the catchment height, catchment slope and aspect, and flow path length, using parallel processing algorithms including the recommended multiple flow direction algorithm. This set of algorithms processes a digital elevation model (DEM) downwards from the highest to the lowest cell.
No longer supported with SAGA GIS 2.1.3+. See rsaga.topdown.processing().

Usage

rsaga.parallel.processing(
  in.dem,
  in.sinkroute,
  in.weight,
  out.carea,
  out.cheight,
  out.cslope,
  out.caspect,
  out.flowpath,
  step,
  method = "mfd",
  linear.threshold = Inf,
  convergence = 1.1,
  env = rsaga.env(),
  ...
)

Arguments

in.dem	input: digital elevation model (DEM) as SAGA grid file (default file extension: .sgrd)
in.sinkroute	optional input: SAGA grid with sink routes
in.weight	optional intput: SAGA grid with weights
out.carea	output: catchment area grid
out.cheight	optional output: catchment height grid
out.cslope	optional output: catchment slope grid
out.caspect	optional output: catchment aspect grid
out.flowpath	optional output: flow path length grid
step	integer >=1: step parameter
method	character or numeric: choice of processing algorithm: Deterministic 8 ("d8" or 0), Rho 8 ("rho8" or 1), Braunschweiger Reliefmodell ("braunschweig" or 2), Deterministic Infinity ("dinf" or 3), Multiple Flow Direction ("mfd" or 4, the default), Multiple Triangular Flow Direction ("mtfd", or 5).
linear.threshold	numeric (number of grid cells): threshold above which linear flow (i.e. the Deterministic 8 algorithm) will be used; linear flow is disabled for linear.threshold=Inf (the default)
convergence	numeric >=0: a parameter for tuning convergent/ divergent flow; default value of 1.1 gives realistic results and should not be changed
env	list, setting up a SAGA geoprocessing environment as created by rsaga.env()
...	further arguments to rsaga.geoprocessor()

Details

Refer to the references for details on the available algorithms.

Value

The type of object returned depends on the intern argument passed to the rsaga.geoprocessor(). For intern=FALSE it is a numerical error code (0: success), or otherwise (the default) a character vector with the module's console output.

Note

This function uses module Parallel Processing (version 2.0.7+: Catchment Area (Parallel) from SAGA library ta_hydrology.

The SAGA GIS 2.0.6+ version of the module adds more (optional) input and output grids that are currently not supported by this wrapper function. Use rsaga.geoprocessor() for access to these options, and see rsaga.get.usage("ta_hydrology","Catchment Area (Parallel)") for information on new arguments.

Author(s)

Alexander Brenning (R interface), Olaf Conrad (SAGA module), Thomas Grabs (MTFD algorithm)

References

Deterministic 8:

O'Callaghan, J.F., Mark, D.M. (1984): The extraction of drainage networks from digital elevation data. Computer Vision, Graphics and Image Processing, 28: 323-344.

Rho 8:

Fairfield, J., Leymarie, P. (1991): Drainage networks from grid digital elevation models. Water Resources Research, 27: 709-717.

Braunschweiger Reliefmodell:

Bauer, J., Rohdenburg, H., Bork, H.-R. (1985): Ein Digitales Reliefmodell als Vorraussetzung fuer ein deterministisches Modell der Wasser- und Stoff-Fluesse. Landschaftsgenese und Landschaftsoekologie, H. 10, Parameteraufbereitung fuer deterministische Gebiets-Wassermodelle, Grundlagenarbeiten zu Analyse von Agrar-Oekosystemen, eds.: Bork, H.-R., Rohdenburg, H., p. 1-15.

Deterministic Infinity:

Tarboton, D.G. (1997): A new method for the determination of flow directions and upslope areas in grid digital elevation models. Water Ressources Research, 33(2): 309-319.

Multiple Flow Direction:

Freeman, G.T. (1991): Calculating catchment area with divergent flow based on a regular grid. Computers and Geosciences, 17: 413-22.

Quinn, P.F., Beven, K.J., Chevallier, P., Planchon, O. (1991): The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models. Hydrological Processes, 5: 59-79.

Multiple Triangular Flow Direction:

Seibert, J., McGlynn, B. (2007): A new triangular multiple flow direction algorithm for computing upslope areas from gridded digital elevation models. Water Ressources Research, 43, W04501.

See Also

rsaga.topdown.processing(), rsaga.wetness.index(), rsaga.geoprocessor(), rsaga.env()

Examples

## Not run: 
# SAGA GIS 2.0.6+:
rsaga.get.usage("ta_hydrology","Catchment Area (Parallel)")
# earlier versions of SAGA GIS:
#rsaga.get.usage("ta_hydrology","Parallel Processing")
# execute model with typical settings:
rsaga.parallel.processing(in.dem = "dem", out.carea = "carea", out.cslope = "cslope")
# cslope is in radians - convert to degree:
fac = round(180/pi, 4)
formula = paste(fac, "*a", sep = "")
rsaga.grid.calculus("cslope", "cslopedeg", formula)

## End(Not run)

RSAGA documentation built on Dec. 10, 2022, 1:12 a.m.