Ubuntu Manpage: r.surf.contour - Generates surface raster map from rasterized contours.

NAME

       r.surf.contour  - Generates surface raster map from rasterized contours.

KEYWORDS

       raster, surface, interpolation

SYNOPSIS

       r.surf.contour
       r.surf.contour --help
       r.surf.contour input=name output=name  [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input raster map containing contours

       output=name [required]
           Name for output raster map

DESCRIPTION

r.surf.contour creates a raster elevation map from a rasterized contour map. Elevation values are
determined using procedures similar to a manual methods. To determine the elevation of a point on a
contour map, an individual might interpolate its value from those of the two nearest contour lines
(uphill and downhill).

r.surf.contour works in a similar way. Initially, a vector map of the contour lines is made with the
elevation of each line as an attribute. When the program v.to.rast is run on the vector map, continuous
"lines" of rasters containing the contour line values will be the input for r.surf.contour. For each cell
in the input map, either the cell is a contour line cell (which is given that value), or a flood fill is
generated from that spot until the fill comes to two unique values. So the r.surf.contour algorithm
linearly interpolates between contour lines. The flood fill is not allowed to cross over the rasterized
contour lines, thus ensuring that an uphill and downhill contour value will be the two values chosen.
r.surf.contour interpolates from the uphill and downhill values by the true distance.

Parameters:
input=name
Name of an existing raster map that contains a set of initial category values (i.e., some cells
contain known elevation values (denoting contours) while the rest contain NULL values).

output=name
Name to be assigned to new output raster map that represents a smooth (e.g., elevation) surface
generated from the known category values in the input raster map layer.

An existing MASK raster map is respected for both reading input and writing output.

NOTES

       r.surf.contour works well under the following circumstances: 1) the contour lines extend to the the  edge
       of  the  current  region, 2) the program is run at the same resolution as that of the input map, 3) there
       are no disjointed contour lines, and 4) no  spot  elevation  data  BETWEEN  contour  lines  exist.   Spot
       elevations  at  the  tops  of hills and the bottoms of depressions, on the other hand, improve the output
       greatly.  Violating these constraints will cause non-intuitive anomalies to appear  in  the  output  map.
       Run  r.slope.aspect
        on r.surf.contour results to locate potential anomalies.

       The  running of r.surf.contour is very sensitive to the resolution of rasterized vector map.  If multiple
       contour lines go through the same raster, slight anomalies may occur.  The  speed  of  r.surf.contour  is
       dependent  on how far "apart" the contour lines are from each other (as measured in raster cells).  Since
       a flood fill algorithm is used, the program’s running time will  grow  exponentially  with  the  distance
       between contour lines.

EXAMPLE

       Example  to create contour lines from elevation model, then recreating DEM from these contour lines along
       with differences analysis (North Carolina sample data set):
       g.region raster=elevation -p
       # get minimum elevation value
       r.univar elevation
       # generate vector contour lines
       r.contour input=elevation output=contours_5m step=5 minlevel=50
       # rasterize contour lines
       v.info -c contours_5m
       v.to.rast input=contours_5m output=contours_5m use=attr attribute_column=level
       # generate DEM from rasterized contour lines
       r.surf.contour input=contours_5m output=elevation_from_cont5m
       # calculate difference map
       r.mapcalc "diff = elevation - elevation_from_cont5m"
       r.colors diff color=differences
       # analyze differences statistically
       r.univar diff

AUTHOR

       Chuck Ehlschlaeger, U.S. Army Construction Engineering Research Laboratory

SOURCE CODE

       Available at: r.surf.contour source code (history)

       Accessed: Friday Apr 04 01:19:39 2025

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       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                               r.surf.contour(1grass)