[GRASS-dev] Re: [GRASS-user] mask in PERMANENT affect on other mapsets during reprojection

[Jarosław Jasiewicz]

Hamish pisze:
> Hamish:
>   
>>> side-suggestion: before running r.proj run v.in.region
>>> in the source location then v.proj from the taget location.
>>>       
>
> Jarekj wrote:
>   
>> I always do as you suggest (in general other methods (with
>> cs2cs)  in grass are to complicated),
>>     
>
> sorry, I don't understand. is that to say that GRASS is easier or harder
> than other methods? (ie, if harder, what areas need improving and what is
> a clearer (proj4/gdal) method to use?)
>
>   
In general in grass help is also suggrested method with manual 
recalculating extension of grass region with cs2cs (and there is also 
wrapper for that program), the method you suggested is also in help, 
both method are "grass" method

Many Thanks for information you added below, It will help me to finish 
my work faster
Jarek
>   
>> Script must additionally check if no mask is present in PERMANENT or
>> it is a bug and will be removed in the feature
>>     
> ....
>   
>> So as I understand the problem will heppen when I have mask in mapset in
>> source which is named as my target mapset in target location: ussually
>> it will concern PERMANENT?
>>     
>
>
> * Maps are searched for in the current mapset search path. (g.mapsets)
>
> * PERMANENT is, by default, in the map search path. (hence the name)
>
> * If you like you can use g.mapsets to remove PERMANENT from the (source
>   mapset's) search path, then later re-add it, but that may leave you
>   with a damaged mapset if the script exits before the path is restored.
>
> * You can switch between mapsets/locations within your script using the
>   g.mapset (without an "s" at the end) module.
>
> * When raster maps are read, the mapset search path is searched for a map
>   called MASK. If a map by that name is found in the search path then it
>   is applied as the map of interest is read from the disk.
>
> * As Glynn noted, the module internally switches the current mapset, and
>   so the for the time when the source mapset becomes the current mapset
>   if there is a MASK map in the (source) search path, it will be used.
>   (AFAIU)
>
> work arounds include -
>
> o temporarily switching into the source mapset with g.mapset (no "s"),
>   removing everything but the current mapset from the source mapset's
>   search path with g.mapsets (with an "s"), then switching back to the
>   target mapset before running r.proj, then after r.proj is done going
>   back and adding PERMANENT+any others removed back into the search path.
>   As hinted above I think this solution to be rather poor.
>
> o temporarily switching into the source mapset with g.mapset (no "s"),
>   and then run "g.findfile element=cell file=MASK". The result (and exit
>   code) will tell you if there is a map called MASK in the search path.
>   What you do then is up to you. Maybe switch back to the original
>   mapset/location and exit with an error or proceed with a warning.
>
> o change the method used by the r.proj code. (as suggested by Glynn)
>
>
> hope that makes the "why" a bit clearer.
>
>
> Hamish
>
>
>
>       
>