[Chameleon] Problem with Scale widget

Jacob Delfos jacob.delfos at maunsell.com
Thu Sep 23 20:24:29 EDT 2004


One thing that can could possibly cause this is if your original map-extent does not have exactly the same aspect ratio as your mapsize (different shape). When your application first starts up, it might take your map-extent from your base settings. If, for example, your map image is square, but your extents rectangular, it can mess up the calculations. Chameleon will assume the bounding coordinates are as specified by you, whereas your mapimage will resort to the nearest extent that fits (and thus the actual mapextent and scale displayed are not the same as the extent and scale variables). That is why I always use a default map-extent with bounding coordinates I got out off chameleon itself.


-----Original Message-----
From: chameleon-bounces at lists.maptools.org [mailto:chameleon-bounces at lists.maptools.org] On Behalf Of Berend Veldkamp
Sent: 23 September 2004 16:37
To: chameleon at lists.maptools.org
Subject: Re: [Chameleon] Problem with Scale widget

I'm using 1.99 as well. Most of the time it calculates the exact scale, 
only at one particular mapsize there's a deviation.


Jacob Delfos wrote:

> Berend,
> Which version of chameleon are you using? I'm using my own scaletool 
> with a javascript calculation based on the current mapextents, and the 
> printsize. It then zooms to the newly calculated map-extents. 
> For latlong, I take into consideration the longitude. I use the same 
> calculation in CWC 1.0.4 as I do in chameleon 1.99, but only in version 
> 1.99 I managed to get to the same scale as the user enters. E.g. in CWC 
> 1.0.4, my calculated extent resulted in a scale slightly different from 
> what was 'predicted' (1:100005, in stead of 1:100000). I thought this 
> was due to a ronding error).
> But in chameleon 1.99, I always get the right scale, even if it is 
> recalculating from 1:500 to 1:5000000. I use the same calculation, but 
> for some reason the mapextents can be set more precisely in 1.99. 
> Whatever has changed in chameleon 1.99 worked well for me, but did not 
> find its way into the normal scale widget.
> Paul, where can I see the calculation for the scale widget? Do I need to 
> check the mapserver source code for this?
> regards,
> Jacob

Berend Veldkamp - ARIS
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