Calculates local morphometric terrain attributes (i.e. slope, aspect, and curvatures). Intended for use with SAGA v 2.1.1+. For older versions use rsaga.local.morphometry().
rsaga.slope.asp.curv(
in.dem,
out.slope,
out.aspect,
out.cgene,
out.cprof,
out.cplan,
out.ctang,
out.clong,
out.ccros,
out.cmini,
out.cmaxi,
out.ctota,
out.croto,
method = "poly2zevenbergen",
unit.slope = "radians",
unit.aspect = "radians",
env = rsaga.env(),
...
)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 (default) a character vector with the module's console output.
input: digital elevation model as SAGA grid file (.sgrd)
optional output: slope
optional output: aspect
optional output: general curvature (1 / map units)
optional output: profile curvature (vertical curvature; 1 / map units)
optional output: plan curvature (horizontal curvature; 1 / map units)
optional output: tangential curvature (1 / map units)
optional output: longitudinal curvature (1 / map units) Zevenbergen & Thorne (1987) refer to this as profile curvature
optional output: cross-sectional curvature (1 / map units) Zevenbergen & Thorne (1987) refer to this as the plan curvature
optional output: minimal curvature (1 / map units)
optional output: maximal curvature (1 / map units)
optional output: total curvature (1 / map units)
optional output: flow line curvature (1 / map units)
character algorithm (see References):
0 Maximum Slope - Travis et al. (1975) ("maxslope")
1 Max. Triangle Slope - Tarboton (1997) ("maxtriangleslope")
2 Least Squares Fit Plane - Costa-Cabral & Burgess (1996) ("lsqfitplane")
3 Fit 2nd Degree Polynomial - Evans (1979) ("poly2evans")
4 Fit 2nd Degree Polynomial - Heerdegen and Beran (1982) ("poly2heerdegen")
5 Fit 2nd Degree Polynomial - Bauer et al. (1985) ("poly2bauer")
6 default: Fit 2nd Degree Polynomial - Zevenbergen & Thorne (1987) ("poly2zevenbergen")
7 Fit 3rd Degree Polynomial - Haralick (1983) ("poly3haralick")
character or numeric (default "radians"):
0 "radians"
1 "degrees"
2 "percent"
character or numeric (default is 0, or "radians"):
0 "radians"
1 "degrees"
list, setting up a SAGA geoprocessing environment as created by rsaga.env()
further arguments to rsaga.geoprocessor()
Alexander Brenning and Donovan Bangs (R interface), Olaf Conrad (SAGA module)
Profile and plan curvature calculation (out.cprof, out.cplan) changed in SAGA GIS 2.1.1+ compared to earlier versions. See the following thread on sourceforge.net for an ongoing discussion: https://sourceforge.net/p/saga-gis/discussion/354013/thread/e9d07075/#5727
General references:
Jones KH (1998) A comparison of algorithms used to compute hill slope as a property of the DEM. Computers and Geosciences. 24 (4): 315-323.
References on specific methods:
Maximum Slope:
Travis, M.R., Elsner, G.H., Iverson, W.D., Johnson, C.G. (1975): VIEWIT: computation of seen areas, slope, and aspect for land-use planning. USDA F.S. Gen. Tech. Rep. PSW-11/1975, 70 p. Berkeley, California, U.S.A.
Maximum Triangle Slope:
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.
Least Squares or Best Fit Plane:
Beasley, D.B., Huggins, L.F. (1982): ANSWERS: User's manual. U.S. EPA-905/9-82-001, Chicago, IL, 54 pp.
Costa-Cabral, M., Burges, S.J. (1994): Digital Elevation Model Networks (DEMON): a model of flow over hillslopes for computation of contributing and dispersal areas. Water Resources Research, 30(6): 1681-1692.
Fit 2nd Degree Polynomial:
Evans, I.S. (1979): An integrated system of terrain analysis and slope mapping. Final Report on grant DA-ERO-591-73-G0040. University of Durham, England.
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 zur Analyse von Agrar-Oekosystemen, eds.: Bork, H.-R., Rohdenburg, H., p. 1-15.
Heerdegen, R.G., Beran, M.A. (1982): Quantifying source areas through land surface curvature. Journal of Hydrology, 57.
Zevenbergen, L.W., Thorne, C.R. (1987): Quantitative analysis of land surface topography. Earth Surface Processes and Landforms, 12: 47-56.
Fit 3.Degree Polynomial:
Haralick, R.M. (1983): Ridge and valley detection on digital images. Computer Vision, Graphics and Image Processing, 22(1): 28-38.
For a discussion on the calculation of slope by ArcGIS check these links:
https://community.esri.com/?c=93&f=1734&t=239914
https://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?topicname=how_slope_works
rsaga.local.morphometry(), rsaga.parallel.processing(), rsaga.geoprocessor(), rsaga.env()
if (FALSE) {
# Simple slope, aspect, and general curvature in degrees:
rsaga.slope.asp.curv("lican.sgrd", "slope", "aspect", "curvature",
method = "maxslope", unit.slope = "degrees", unit.aspect = "degrees")
# same for ASCII grids (default extension .asc):
rsaga.esri.wrapper(rsaga.slope.asp.curv,
in.dem="lican", out.slope="slope",
out.aspect = "aspect", out.cgene = "curvature",
method="maxslope", unit.slope = "degrees", unit.aspect = "degrees")
}
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