Note: This document is for an older version of GRASS GIS that is outdated. You should upgrade, and read the current manual page.
NAME
libgrass_rli - r.li landscape index support library
DESCRIPTION
r.li.daemon provides support for landscape index calculations on raster
maps. It hides the management of areas, defined using r.li.setup
command. It is not used like a standalone program, but its functions are
a library used by all r.li.[index] commands.
This description is a tutorial for new index definition.
The developer has only to focus on a unique area, like in mathematical definitions, and
has to write a C implementation of it.
The areas are defined using a struct called area_des and it members are
explained in the source code (doxygen) documentation.
To write a new index only two steps are needed:
-
Define a function and insert its declaration on file index.h in r.li.daemon
folder, which contains all index declarations. This function must be of this kind:
int index(int fd, char ** par, area_des ad, double * result)
where:
- fd is the raster map descriptor
- par is a matrix for special parameter (like argv in main)
- ad is the area descriptor
- result is where to put the index calculation result
This function has to return 1 on success and 0 otherwise.
-
Create a main for command line arguments parsing, and call the function
int calculateIndex(char * file, int f(int, char** area_des, double *), char **parameters, char *raster, char *output);
from the r.li library, for starting raster analysis.
It follows the meaning of parameters:
- file name of configuration file created using r.li.setup
- f pointer to index function defined above
- parameters pointer to index special parameters
- raster name of raster to use
- output output file name
Compile it using a changed Makefile based on the file for r.li.patchdensity.
NOTES
Using GRASS library function to access raster rows can slow down moving windows
execution. It is recommended to use
RLI_get_cell_row(int, int, area_des)
RLI_get_fcell_row(int, int, area_des)
RLI_get_dcell_row(int, int, area_des)
to use an ad hoc build memory management developed to speed up the system.
The documentation is in doxygen files.
SEE ALSO
old r.le manual
r.li - package overview
r.li.setup
REFERENCES
McGarigal, K., and B. J. Marks. 1995. FRAGSTATS: spatial pattern
analysis program for quantifying landscape structure. USDA For. Serv.
Gen. Tech. Rep. PNW-351. (PDF)
AUTHORS
Claudio Porta and Lucio Davide Spano, students of Computer Science
University of Pisa (Italy).
Commission from Faunalia Pontedera (PI)
Rewritten from "r.le.setup" by William L. Baker
This program is free software under the GPL (>=v2)
Read the COPYING file that comes with GRASS for details.
Last changed: $Date: 2014-03-24 04:40:14 -0700 (Mon, 24 Mar 2014) $
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