Re: Projection map ratio problem

Something to keep in mind is that the projections use the center of the screen as the
center latitude and center longitude. In other words, you're not sliding a fixed
projection around under a window, you're recomputing the projection for each pan/zoom.
That could be what you're seeing.

It's precisely this behavior that makes it hard to use openmap as a WMS client or
server. The xxxview projections were an initial attempt at changing this.

    Allan

rs@syncline.com wrote:

> Mercator, by default for MapBean. Are you saying that the
> ratio of pixel and geographic rectangles should be
> different in Mercator, or are you saying that the
> variability in the ratios will change across the earth?
>
> Don Dietrick wrote:
> >
> > Hi Raj,
> >
> > What projection were you using to run these tests? I would expect them
> > to be different for different projections, and for different latitudes
> > within the same projection. This is affected by the degree/pixel ratio
> > characteristic of a projection, which is likely variable in most cases,
> > depending on latitude. Equal Arc projections (constant degree/pixel
> > ratios) should be OK, though, like the LLXY projection and the CADRG
> > projection within the same zone.
> >
> > - Don
> >
> > rs@syncline.com wrote:
> > >
> > > I've been doing some tests, and it seems that the ratio
> > > of the MapBean's screen width and height (r) is different than
> > > the ratio of the MapBean's geographic width and height (geor).
> > > See the results of a few extents below. Can anyone explain
> > > what may be happening here?
> > >
> > > minx -130.5 -84.2403 -85.2855
> > > maxx 131.0625 -75.2403 -74.1951
> > > miny -78.062 29.31935 28.64211
> > > maxy 78.06198 36.77261 37.37486
> > > w 465 465 573
> > > h 460 460 539
> > > gr 1.675351 1.207526 1.26997
> > > r 1.01087 1.01087 1.06308
> > >
> > > thanks,
> > > Raj
> > >
> > > --
> > > Raj Singh, Syncline
> > > rs@syncline.com
> > > +1(617)986-1000
> > > MapCiti.com...it's your town on the web
> > >
> > > --
> > > [To unsubscribe to this list send an email to "majdart@bbn.com"
> > > with the following text in the BODY of the message "unsubscribe openmap-users"]
>
> --
> Raj Singh, Syncline
> rs@syncline.com
> +1(617)986-1000
> MapCiti.com...it's your town on the web
>
> --
> [To unsubscribe to this list send an email to "majdart@bbn.com"
> with the following text in the BODY of the message "unsubscribe openmap-users"]

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