[Mapserver-users] Rasterization help, TIF->SHP

[David Monterroso Cabello]

Thorsten Fischer wrote:

>On Mon, 2003-06-23 at 22:36, David Monterroso Cabello wrote:
>  
>
>>Ed McNierney wrote:
>>
>>    
>>
>>>I think you're mixing a few apples and oranges here.
>>>
>>>"Rasterization" is the process of converting vector data to raster data, 
>>> 
>>>      
>>>
>>Umm, i'm also interested in "the other way", i mean vectorization of  
>>raster data. I've some raster images that are georeferenced and are 
>>formed only from lines over a white background. Do you know about any 
>>tool for the unix world that convert that into vector data (shapefile or 
>>anything) automatically?, perhaps grass??.
>>    
>>
>
>There is no such thing as a tool where you can just click a button and
>it converts raster data into vector data. As Ed said, this is a highly
>specialized task. It has not been generically automated yet, and as far
>as i can see it is more than unlikely that it ever will be.
>  
>
Well, i understand there is no "one click" application that will deliver 
a perfect shape, but what im looking for is an application that with the 
correct  configuration, and parameters  can be launched  from a script, 
and then convert the raster into vector data automatically, i don't know 
if it is impossible but as my data is always the same i think i still 
have a chance to automate it.

>'Simple' black lines on a white background sounds easy, but it is not.
>Imagine your program finds lines in your images and identifies an
>intersection of lines. How is the software supposed to know which parts
>of the intersection belong to which line? In every case you will have to
>do some manual work afterwards, and in this case you usually can just
>load the map into some GIS and digitize the whole thing by hand.
>  
>
    Well, i know sometimes there will be some errors whithin the 
process, but i think i can live with that, i need it only for graphic 
representation, so it doesn't have to be perfect.

>As I usually say before the start of seminars and workshops: i got a
>computer scientist background, not a cartographic or geographic one. So
>please correct me if I said something terribly wrong :)
>  
>
    Well, i'm in the same situation, but my knowledge about GIS is much 
much much smaller i  think ;). I  will try GRASS, what i fear is that  
perhaps i can't automate the whole process, but we'll see...

>
>hth,
>
>thorsten
>
>  
>
David.