Re: [OpenMap Users] Bug in LLXY projection

Hi Keith,

Thanks for sending this in, I'll add the change to the package. It
does make the LLXY projection work much better.

- Don

On Mar 25, 2004, at 4:28 PM, Keith Alphonso wrote:

> I found the following bug in the LLXY projection code:
>
> This is the code as it stands in ver 4.6
> ==============================================
> protected void computeParameters() {
> Debug.message("proj", "LLXY.computeParameters()");
> super.computeParameters();
>
> // compute the offsets
> hy = height/2;
> wx = width/2;
> // Degrees longitude of the center of the projection.
> cLon = ProjMath.radToDeg(ctrLon);
> cLat = ProjMath.radToDeg(ctrLat);
> ppd = world.x/360f;
>
> float latLimit = 90f - ((float)hy / ppd);
>
> if (cLat > latLimit) {
> cLat = latLimit;
> ctrLon = ProjMath.degToRad(cLat);
> } else if (cLat < -latLimit) {
> cLat = -latLimit;
> ctrLon = ProjMath.degToRad(cLat);
> }
>
> if (Debug.debugging("llxy")) {
> Debug.output("LLXY.computeParameters: with center lat:" +
> cLat +
> ", lon:" + cLon + " | width:" + width +
> ", height:" + height + " | scale:" + scale);
> }
> }
>
> This is how I believe the code should look:
> ====================================================
> protected void computeParameters() {
> Debug.message("proj", "LLXY.computeParameters()");
> super.computeParameters();
>
> // compute the offsets
> hy = height/2;
> wx = width/2;
> // Degrees longitude of the center of the projection.
> cLon = ProjMath.radToDeg(ctrLon);
> cLat = ProjMath.radToDeg(ctrLat);
> ppd = world.x/360f;
>
> float latLimit = 90f - ((float)hy / ppd);
>
> //Add check for zoom allowing more than 90 degrees viewable
> if (latLimit < 0.0f)
> latLimit = 0.0f;
>
> if (cLat > latLimit) {
> cLat = latLimit;
> //Should set ctrLat here
> //ctrLon = ProjMath.degToRad(cLat);
> ctrLat = ProjMath.degToRad(cLat);
> } else if (cLat < -latLimit) {
> cLat = -latLimit;
> ctrLon = ProjMath.degToRad(cLat);
> }
>
> if (Debug.debugging("llxy")) {
> Debug.output("LLXY.computeParameters: with center lat:" +
> cLat +
> ", lon:" + cLon + " | width:" + width +
> ", height:" + height + " | scale:" + scale);
> }
> }
>
>
> Do you agree with this assessment? With this change, the LLXY
> projection
> will be shown centered instead of at the top, and the projection calcs
> work.
>
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