Y. J. Chun a écrit :
> My understanding is.
> CoordinateSystem means x y relations.
> CoordinateReferenceSystem is CS with exact numbers.
Again I'm not sure what you mean.
CoordinateSystem said how the geometric properties (length, angle, etc.) are to
be computed from coordinates. This is a mathematical concept not related to any
particular material object (the Earth, Mars, a plane, etc.). In other words, we
have no idea where the coordinate (0,0) is located in the real world.
CoordinateReferenceSystem is a CoordinateSystem attached to the Earth through a
Datum. It defines where the coordinate (0,0) is located in the real world.
> so given lon/lat point,
> WGS84 CRS -> ProjectedCRS
> gives meters.
> this meter need to be affine transformed to be pixels.
Right.
> image pixel -- (AffineTransform) --> meters -- (inverse proj crs -> wgs crs)
> --> lon/lat ?
Right.
> WGS83 CRS (which is lon/lat) --> projected crs (meters) --- (affine
> transform) --> screen pixels ?
Right.
> So my world2screen means lon/lat to pixel. Do you mean the same?
> It seems your world means meters (the result of projected crs conversion).
It depends what you call "world": the GeographicCRS or the ProjectedCRS.
> Another question arises. Is it better to use EngineeringCRS for this
> specific screen crs?
No, I would rather suggest to keep going with DerivedCRS.
Martin
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