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:
- 1
- 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.
- 6
- 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 12:43:14 +0100 (Mon, 24 Mar 2014) $
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