[GRASS-user] map resolution
Markus Neteler
neteler at osgeo.org
Tue Nov 1 17:10:26 EDT 2011
On Tue, Nov 1, 2011 at 4:53 PM, Chi Kit Lau <lau.chikit11 at gmail.com> wrote:
> Dear GRASS users,
>
> sorry for the beginner's question. How do I work out the maximum
> achievable resolution when rasterizing a vector map on a scale
> 1:10000? In other words what is the resolution of a map with a scale
> 1:10000?
This may be interesting for you
"Cartographic limitations [for vector maps]"
http://www.searchmesh.net/default.aspx?page=1817
Markus
PS: For raster maps, if you are using a scanner (adapted from
our GRASS book):
Suppose that the scale of the scanned map is 1:10,000. Thus, one centimeter
on the map is equivalent to 10,000cm on the ground.
Scan resolution, e.g. 300dpi:
300 lines lines
300dpi = ----------- = 118.11 ---------
2.54cm cm
Now we can calculate the on-ground distance that
corresponds to the length of a raster cell:
distance on the ground 10, 000cm cm m
---------------------------- = --------------- = 84.75 ------ = 0.85 ----
scanned lines per cm 118.11lines line
line
The resulting value of 0.85m is the spatial pixel resolution of the scanned
map at the 300dpi scan resolution. If you want the spatial resolution to
be an integer, do the inverse calculation and adjust the scanning resolution
accordingly.
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