Scaling vector data

Philip Verhagen philip at
Thu Mar 13 06:52:00 EST 1997

> We have a raster map and a vector map of the same area (i.e. we want to overlay
> the vector onto the raster). However, they are at different scales. The raster
> map is at a scale of 1:1000 while the vector map is at a scale of 1:2400. Since
> the raster map is an image, we do not want to lose any details of the image.
> Therefore, I was wondering if there was any way to scale the vector map to a
> 1:1000 scale.

OK, a few words on scale then. Scale can be defined as the level of detail
at which data is mapped. For polygon maps, a minimum size of 0.25 x 0.25 cm
on the map sheet is usually the level of detail that is used. This would mean
a 2.5 x 2.5 m area on 1:1000 and 6 x 6 m on 1:2400. For line maps, I
usually assume that a feature with a size of 1 mm can be digitized with
reasonable accuracy. There is to my knowledge no way of 'imposing' a 1:1000 
scale on a 1:2400 map, as the information included at the finer scale level is 
not present at the coarser level.  Aggregating the minimum polygon size  to a 
larger size (i.e. increasing the pixel size) is of course always possible. The 
only thing I can suggest is use the data as it is: the 1:2400 overlay will 
just look a bit ugly...

Philip Verhagen


                     philip at

                              R  A  A  P

                        Plantage Muidergracht 14
                          1018 TV Amsterdam
                           The Netherlands

                        tel: +31 (20) 421 62 00
                        fax: +31 (20) 421 42 90



More information about the grass-user mailing list