[OSRS-PROJ] Datum Shifting

Martin Manningham martinm at six.net
Wed Jul 5 21:49:13 EDT 2000

Martin Manningham wrote:

> In the other hand (I agree with Mr Evenden here): Datum transformation
> isn't as easy to handle than projection transformation. Most of the
> time, this is only a shift applied to a certain system of coordinates of
> a small map, and people are using tables to perform this operation.
> Tables are difficult to handle since they could be big and their format
> could change over time. But they are most of the time more flexible and
> precise Of course, there is some mathematical transformations of the
> requested shifts from one datum to another (nad27 to WGS84 or stuff like
> this) and this must be put into consideration on this situation...

Sorry about the last paragraph, I was composing this email when I sent this email
before completion by mistake.

To finish what I was saying, a problem of datum transformation is there is no easy
way to go from one datum to another, and a new library will have to be as modular
than possible to respect the variety of existing datum transformation. Or the
library will have to be build to handle all the possible datum transformation,
including datum table handling.

This problem isn`t an easy one. I think integration of this transformation is
important, but how to handle every possible datum transformation without increasing
the complexity of the API or string representation of a projection?


Martin Manningham

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