[GRASSLIST:3247] Re: Rastering

[J.c.m. van der Kwast]

Hi Karine,

Yes, I've checked region settings, there's no problem at all. I ddin't 
mention it before, but I've also tried to buffer the cells (r.grow (1 
cell) and r.buffer, and with mapcalc tried to define them as areas again 
( in mapcalc use some like newfile = file + buffered_file). This does'nt 
seem to work as well, unless the buffer is like 5 m which would 
exaggerate the features enormously. Also the neighborhood module, has 
been tried. Same story, you must exaggerate enormously (e.g. buffer 9 
cells up to 13 cells). I've been trying afterwards to thin the map with 
r.thin leaving me the result I've started out with. I think the problem 
has more to do with scale and resolution. Well I'll keep on trying this 
and that, thanks anyway,

Greetings,

Sjors  




Karine ZUERCHER wrote:

>Sjors,
>
>Have you checked the region settings (g.region -p) just before doing the 
>v.to.rast?
>You should have the nsres & ewres equal to 1 &  rows & cols 5000.
>
>Hope that may help
>In Kindness
>
>Karine
> 
>On Wednesday 27 February 2002 15:43, J.c.m. van der Kwast wrote:
>
>>Hi everybody,
>>
>>For some time now I'm wrestling with the rasterization of thin
>>linear/area objects. The case is as follows, xy projection, area 5000 x
>>5000 m (or units), grid 1 x1. I've got thin areas of 3 m wide and trying
>>to raster them. I would expect to see them as thin linear objects in a
>>raster map of the whole area. But the areas are broken. When zooming in
>>extremely then the areas seem to form lines or areas again, but are they
>>continuous? Maybe it has something to do with the scale?
>>When given a z value and patched with a dem, the dem is correctly
>>displayed but the thin areas are broken into pieces (as they are in the
>>whole raster map). Does it mean that I should divide the map up into
>>small portions with a desirable resolution, raster them and patch them
>>back together in the desired resolution? Personnally I don't think it
>>will help as the areas formed do not seem to be continuous.
>>Some time ago I wrote a mail with the title landscape. The problem is
>>much the same, only with rastering linear features. As my background is
>>not GIS (but agriculture) it could be I'm trying to do something which
>>isn't possible at all. But looking at it logically, a feature of 1 cell
>>in a grid of 1 x1 should at least take the value I've given it. If it
>>doesn't show up at the screen I can live with it. Problem is, it does
>>sometimes will and sometimes won't show up.
>>I've been playing around with a lot of functions and manuals but still
>>this puzzles me greatly. If anyone has any answers, I'd be most grateful,
>>
>>Warm regards,
>>
>>Sjors
>>
>