Alternatively, bitmask-encoded directions can be provided where each bit position corresponds to a specific neighbour. A path will continue to all neighbours with their bit set. This means a path can split and merge. Such bitmasked directions can be created with the -b flag of r.cost and r.walk.
Direction encoding for neighbors of x 135 90 45 7 8 1 180 x 360 6 x 2 225 270 315 5 4 3 degrees bit positions CCW from East
The output raster map will show one or more least-cost paths between each user-provided location(s) and the target points (direction ≤ 0). By default, the output will be an integer CELL map with the id of the start points along the least cost path, and null cells elsewhere.
With the -c (copy) flag, the values raster map cell values are copied verbatim along the path. With the -a (accumulate) flag, the accumulated cell value from the starting point up to the current cell is written on output. With either the -c or the -a flags, the raster_path map is created with the same cell type as the values raster map (integer, float or double). With the -n (number) flag, the cells are numbered consecutively from the starting point to the final point. The -c, -a, and -n flags are mutually incompatible.
The start_coordinates parameter consists of map E and N grid coordinates of a starting point. Each x,y pair is the easting and northing (respectively) of a starting point from which a path will be traced following input directions. The start_points parameter can take multiple vector maps containing additional starting points.
112.5 67.5 157.5 135 90 45 22.5 180 x 0 202.5 225 270 315 337.5 247.5 292.5
v.in.ascii input=- output=start format=point separator=comma <<EOF 638667.15686275,220610.29411765 638610.78431373,220223.03921569 EOF
r.watershed elevation=elev_lid792_1m accumulation=accum drainage=drain_dir
r.mapcalc "drain_deg = if(drain_dir != 0, 45. * abs(drain_dir), null())"
r.path input=drain_deg raster_path=drain_path vector_path=drain_path start_points=start
r.colors map=elev_lid792_1m color=elevation r.relief input=elev_lid792_1m output=relief
d.shade shade=relief color=elev_lid792_1m d.vect map=drain_path color=0:0:61 width=4 legend_label="drainage paths" d.vect map=start color=none fill_color=224:0:0 icon=basic/circle size=15 legend_label=origins d.legend.vect -b
g.region swwake_30m -p # create friction map based on land cover r.recode input=landclass96 output=friction rules=- << EOF 1:3:0.1:0.1 4:5:10.:10. 6:6:1000.0:1000.0 7:7:0.3:0.3 EOF # without Knight's move r.walk -b elevation=elev_ned_30m friction=friction output=walkcost \ outdir=walkdir start_coordinates=635576,216485 r.path input=walkdir start_coordinates=640206,222795 \ raster_path=walkpath vector_path=walkpath # with Knight's move r.walk -b -k elevation=elev_ned_30m friction=friction output=walkcost_k \ outdir=walkdir_k start_coordinates=635576,216485 r.path input=walkdir_k start_coordinates=640206,222795 \ raster_path=walkpath_k vector_path=walkpath_k # without Knight's move and without bitmask encoding (single direction) r.walk elevation=elev_ned_30m friction=friction output=walkcost_s \ outdir=walkdir_s start_coordinates=635576,216485 r.path input=walkdir_s start_coordinates=640206,222795 \ raster_path=walkpath_s vector_path=walkpath_s
Available at: r.path source code (history)
Latest change: Friday Aug 02 05:27:10 2024 in commit: 9cebe70d7893d987c8a5aa3f05099d0688800422
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