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

[Thorsten Fischer]

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.

'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.

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 :)


hth,

thorsten