Rechercher une page de manuel
d.polar
Langue: en
Version: 369310 (fedora - 01/12/10)
Section: 1 (Commandes utilisateur)
Sommaire
NAME
d.polar - Draws polar diagram of angle map such as aspect or flow directionsKEYWORDS
display, diagramSYNOPSIS
d.polard.polar help
d.polar [-x] map=name [undef=float] [eps=string] [--verbose] [--quiet]
Flags:
- -x
Plot using Xgraph- --verbose
Verbose module output- --quiet
Quiet module output
Parameters:
- map=name
Name of raster angle map- undef=float
Pixel value to be interpreted as undefined (different from NULL)- eps=string
Name of optional EPS output file
DESCRIPTION
d.polar calculates and displays a polar diagram of an angle raster map such as aspect, wind direction, or flow. The input angle map orientation must be counter-clockwise (CCW) from east, and the angle map units must be degrees. This refers to the standard orientation of GRASS (e.g., see r.slope.aspect).The radius of the outer circle is defined by the total number of pixels in the map. If the polar diagram does not reach the outer circle, no data (NULL) pixels were found in the map.
The vector in the diagram indicates a prevailing direction, its length the strength of such direction. In case all angle vectors are oriented along the same direction, the length for the vector is maximal (in fact it is equal to length of the most populated bin of the underlying histogram).
As a side effect, the quality of the angle map can be derived from the diagram. Strong spikes may indicate an over-representation of the related angle(s) which happens in particular if integer maps are used.
NOTES
If the eps parameter is used, the diagram is generated as EPS file. If the -x flag is used xgraph is lauched. Otherwise d.polar will use d.graph to draw the plot in the current display frame.If d.polar is used on an aspect map generated by r.slope.aspect, the undef parameter should be set to 0 to distinguish NO DATA (NULL) areas from areas where aspect is undefined (i.e. flat areas).
Polar diagram of aspect map
EXAMPLE
In this example, the polar diagram of the 'aspect' angle map in the Spearfish location is generated:d.polar aspect
SEE ALSO
d.graph, d.histogram, d.rast.arrow, r.slope.aspectXGRAPH REQUIREMENT
Xgraph must be installed for the -x flag to function.AUTHORS
Markus Neteler, ITC-irst, ItalyBruno Caprile, ITC-irst, Italy
Hamish Bowman, Otago University, New Zealand
Last changed: $Date: 2006-10-30 14:34:00 +0100 (Mon, 30 Oct 2006) $
Full index
© 2003-2008 GRASS Development Team
Contenus ©2006-2024 Benjamin Poulain
Design ©2006-2024 Maxime Vantorre