On 08/03/10 16:06, Daniel Morissette wrote:
Jan, Jeff,
If you have ideas of an easier mechanism to help determine scales that
you would like to see added in MapServer then please share them... I'd
be happy to help improve this.
As a rule of thumb, for raster maps I compute the scale that displays
one pixel from the raster file as exactly one screen pixel. The
optimal Maxscale-Minscale breakpoints between two raster maps are
generally exactly in the middle of those basic scales (depends a bit on
format and compression ratio). For vector maps I start with the scale
needed to display
the whole map on a 1000*1000 screen (becoming the largest Minscale) and
try to figure out efficient breakpoints for smaller scales by counting
the number of elements in the files. Most of the time, my
Maxscale/Minscale pairs for different layers are derived by
multiplying/dividing by two, on the basis of those basic values.
Those are just rules of thumb of course. I'm not sure whether they could
or should be generalized into MapServer directives.
Jan
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