[MAPSERVER-USERS] Problems calculating MAXSCALES

Rob gis at vanbooth.com
Thu Aug 14 04:03:58 EDT 2008


>2) ESRI desktop scale computations do not match MapServer computations. Again true probably because
>the number of pixels per inch value used in each package is different. The underlying pixel/extent model
>shouldn't matter I guess.

We had to modify the RESOLUTION in the mapfile to 96 to match the ESRI
values.  Hence our scale calculations agreed with theirs previously.

> In this case I think Rob is seeing the effect of 1) and if so would need to adjust his layer MAXSCALE and
> move on.

Unless I'm mistaken though, the margin of error is based on the image
size, and this could be different values depending on the map size
selected on the GIS client.  That means that whilst modifying the
MAXSCALE values I can reduce the margin of error by estimating a
standard size, but it will never be right for all clients.

I haven't tried a later build yet, but if the code hasn't changed I'd
imagine my problem remains also.


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