GRASS logo

NAME

v.curvature - Calculate curvature. With segment option it reads from standard input: segment_id line_category from to and writes to standard output: segment_id average_curvature average_radius If a segment given runs outside the line, it is cut. If more lines with the same category are found, curvature is not calculated and warning is printed.

KEYWORDS

vector, segment, curvature

SYNOPSIS

v.curvature
v.curvature help
v.curvature [-a] map=name [type=string[,string,...]] [layer=integer] [option=string] [--verbose] [--quiet]

Flags:

-a
Calculate average from absolute values (if not used, segment over 2 successive contrary curves can result in curvature near 0).
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

map=name
Name of input vector map
type=string[,string,...]
Feature type
Options: line,boundary
Default: line
layer=integer
Layer number
A single vector map can be connected to multiple database tables. This number determines which table to use.
Default: 1
option=string
Option
Options: segment,lines
Default: segment
segment: reads segments from standard input
lines: calculate curvature for all sements of all lines

DESCRIPTION

v.curvature calculates average curvature along a segment given by from/to distance measured along the line specified by category.

For individual straight parts of the line, the average curvature as calculated from directions of adjacent parts. An average of specified segment is then calculated as average from curvatures of line parts (lengths of line parts overlapped by specified segment are taken into acount).

This method may be used only if line data digitized with appropriate accuracy, where 'appropriate' depend on an application we want to use it for and on the length of the segment we want to calculate the curvature for.

If user needs curvature for too small segments compared to the density of vertices on lines, the lines should be smoothed beforehand with some other module (this approach is preferred to internal smoothing (interpolating) within v.curvature, because automatic smoothing may often result in unexpected, unwanted shapes, and user should see which data are really processed).

With the 'segment' option, the module reads from 'stdin':

Output is written to 'stdout' in format:
  segment_id average_curvature average_radius

AUTHOR

Radim Blazek, ITC-Irst, Trento, Italy

Last changed: $Date: 2011-11-08 13:56:45 -0800 (Tue, 08 Nov 2011) $


Main index - vector index - Full index

© 2003-2014 GRASS Development Team