Hi Frank,
I appreciate your interest on this, but perhaps taking a closer look at the
Mercator first would be more fruitful. I got a number of replies from the
PROJ4 list that indicate the problem is related to the Mercator
characteristics, i.e.
From: Clifford J Mugnier <[EMAIL PROTECTED]>
>Computing distances is a folly on the Normal Aspect
>Mercator. With two endpoints, just compute the inverse of the cartesian
>coordinates back into latitude and longitude and then compute the correct
>distance with a geodesic inverse.
From: Paul Ramsey <[EMAIL PROTECTED]>
>For a Mercator map of all of California, there is no *right* scale
>bar. The scale at the top will be different from the scale at the
>bottom. This is true of any Mercator map, just actually visible on
>maps of larger areas. So the scale bar Mapserver is generating is
>probably right for *one* part of the map (perhaps the top or bottom?)
>and the scale bar from your paper map is right for *one* part of the
>map (the middle, maybe? or maybe for right where it is?).
>For interactive things, like desktop user interfaces, it is possible
>to quietly cheat. The measuring tool in uDig, for example, projects
>back into geographic coordinates, and does length calculations on the
>spheroid, rather than naively returning the length in the projected
>plane. In this way it is possible to measure distances in meters
>while looking at a map in geographics, or get correct distances from
>a map in mercator.
From: "Craig Miller" <[EMAIL PROTECTED]>
>To get correct distances, you will need to calculated great-circle distance.
I am almost sure that I can implement one of these solutions through php
mapscript, but it will mean circumventing the usual measuring tools . . .
If you are still interested, I will try to re-create the visible
differences from the command line mapserv.exe as you suggest . . .
thanks again for the interest
tim
Tim Norris
At 02:47 PM 10/17/2005, Frank Warmerdam wrote:
On 10/17/05, Kralidis,Tom [Burlington] <[EMAIL PROTECTED]> wrote:
> Thanks for the info. I don't think these instances are using WKT/GML as
> input or output, if that's what you mean. Basic .ovf connection to
> provide WMS output. Is there anything we can do on our end to help with
> this issue? The problem is basically:
Tom / Tim,
If you can reproduce the problem at the commandline with mapserv.exe
from FWTools then just bundle up the minimum data required to reproduce
it along with the commandlne required to invoke it and submit that as a
mapserver bug, reassigned to me.
If you can't reproduce it under those circumstances then perhaps we can
work out a clue as to what is going from that.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
