Martin Desruisseaux created SIS-550:
---------------------------------------
Summary: Give estimation of MathTransform domain
Key: SIS-550
URL: https://issues.apache.org/jira/browse/SIS-550
Project: Spatial Information Systems
Issue Type: Improvement
Components: Referencing
Affects Versions: 1.2
Reporter: Martin Desruisseaux
Assignee: Martin Desruisseaux
Fix For: 1.3
Provides a way to get the ranges of coordinate values which can be used as
inputs in a {{MathTransform}}. They are limits where the transform is
mathematically and numerically applicable. This is *not* the domain of validity
for which a coordinate reference system has been defined, because the new
method ignores "real world" considerations such as datum and country boundaries.
The new method is for allowing callers to crop their data for removing areas
that may cause numerical problems. For example results of Mercator projection
tend to infinity when the latitude value approaches a pole. For avoiding data
structures with unreasonably large values or NaN, we commonly crop data to some
arbitrary maximal latitude value (typically 80 or 84°) before projection. Those
limits are arbitrary, the transform does not become suddenly invalid after a
limit. The new API will need to be extensible for allowing (in the future) some
controls on the criteria for choosing a limit.
Many transforms, in particular all affine transforms, have no mathematical
limits. Again it does not mean that the coordinate operation has no geospatial
domain of validity, but the latter is not the purpose of this method. The new
method is (for example) for preventing a viewer to crash when attempting to
render a world-wide image.
A difficulty is that {{MathTransforms}} are usually part of a larger chain of
transform steps. Users and implementers should not need to search through
transform steps. It should be done automatically by SIS implementation of
{{ConcatenatedTransform}}.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
