[GRASSLIST:6127] Re: Problems with r.le.pixel !?

[Sander Oom]

Dear Martin,

I was viewing the raster in QGIS and the viewer offered three bands. 
However, the raster is indeed only a single band. This is the first time 
I seriously use Grass and Qgis!

The output map still does not make sense thought, and IMHO it is wrong.

A moving window analysis calculates a statistic for a certain window, 
puts the value of the statistic in the center cell of the window and 
then moves on cell up. Then the whole process repeats.

Thus the resulting map should show gradual changes in the statistic, as 
the moving window moved across the map. As the window moves a cell each 
time, the statistic is slightly changed by a new row of cells included 
in the window. This has to go gradually and should not show sharp edge!!

The resulting map should show gradual changes, independent of the shape 
of the window. The shape and size of the window will determine how 
gradual the changes are, i.e. autocorrelation will increase with 
increasing window size.

Running r.le.pixel on a slightly larger map showed dominance values in 
NODATA areas of the original map. Another tell tale sign something is wrong.

The ultimate aim is to run the moving window and then rescale to a 
larger cell size. The larger cell size used is the same as the moving 
window size!

Please correct me if I have completely misunderstood the methodology!?

Cheers,

Sander.

Martin Wegmann wrote:
> On Friday 11 March 2005 04:48, Sander Oom wrote:
> [...]
>>http://www.oomvanlieshout.net/ftp/d3.png
>>http://www.oomvanlieshout.net/ftp/landcover.png
>>
>>The d3 map seems to have three layers, but I can not figure out what
>>they mean. There seems to be some sensible information in the
>>background, but that is over ruled by the square pattern.
> 
> why do you think d3 has three layers? To receive information concerning the 
> colour patterns just use d.legend. 
> The square pattern is caused by your sampling unit setup in r.le.setup - you 
> can choose circle or square and their size. If you set the sampling unit to a 
> smaller size (and to circles) your square pattern might dissappear. 
> 
> cheers Martin
> 
> 

-- 
--------------------------------------------
Dr. Sander P. Oom
Animal, Plant and Environmental Sciences,
University of the Witwatersrand
Private Bag 3, Wits 2050, South Africa
Tel (work)      +27 (0)11 717 64 04
Tel (home)      +27 (0)18 297 44 51
Fax             +27 (0)18 299 24 64
Email   sander at oomvanlieshout.net
Web     www.oomvanlieshout.net/sander
---------------------------------------------