issues with small extents

[Frank Warmerdam]

On 12/20/05, Yewondwossen Assefa <assefa at dmsolutions.ca> wrote:
>  BTW both
> layer and map are set to epsg:4326 but at one point the
> msProjectionsDiffer call returns true ( Igues this is another issue).

Assefa,

This might be worth following up on, but is likely not the
core of your problem.

> Following in the code, It seems that my points get corrupted in
> msProjectPoint.
>
>
> if( out && out->gt.need_geotransform )
>   {
>       double x_out, y_out;
>
>       x_out = out->gt.invgeotransform[0]
>           + out->gt.invgeotransform[1] * point->x
>           + out->gt.invgeotransform[2] * point->y;
>       y_out = out->gt.invgeotransform[3]
>           + out->gt.invgeotransform[4] * point->x
>           + out->gt.invgeotransform[5] * point->y;
>
>       point->x = x_out;
>       point->y = y_out;
> }
>
>  The values inside the invgeotransform array seems to be  wrong but I am
> not sure
>
> invgeotransform    0x00ec6850    double [6]
>     [0]    84.000000000000000    double
>     [1]    20119.760479041917    double
>     [2]    0.00000000000000000    double
>     [3]    47.999999999999993    double
>     [4]    0.00000000000000000    double
>     [5]    20210.526315789473    double
>
> -    geotransform    0x00ec6820    double [6]
>     [0]    -0.0041749999999999999    double
>     [1]    4.9702380952380948e-005    double
>     [2]    0.00000000000000000    double
>     [3]    -0.0023749999999999999    double
>     [4]    0.00000000000000000    double
>     [5]    4.9479166666666665e-005    double
>
>
>   before conversion
>     point->x    0.00000000000000000    double
>     point->y    -1.0000000000000000    double
>
>  after conversion
>     point->x    84.000000000000000    double
>     point->y    -20162.526315789473    double
>
>
>  At what point the invgeotransform   are set ?  I realise this e-mail is
> far from being clear but I am more looking general ideas on how to
> quickly  debug this.

The invgeotransform seems plausible given the geotransform.
It is set in msMapComputeGeotransform() in mapobject.c.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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