Hello Jan
I updated the recently added Krovak projection as below:
* Extracted as much constants as possible out of the loops. They were a fair
amount of trigonometric functions (which are known to be costly) that could
be calculated once for ever, sometime at construction time. The result should
be faster projections.
* Leveraged existing fields like 'scaleFactor' and 'centralMeridian'.
Concequently removed some redundant fields from Krovak. The substitution
was direct for 'scaleFactor', and indirect for 'centralMeridian' (visible
only after some algebraic operations). The result is a projection more
integrated to the existing framework.
* Removed the multiplication or division by 'semiMajor', which were redundant
with the work performed by the MapProjection super-class. It was not obvious
the way the formulas was initially written, but more visible after a little
bit of algebraic rearangement. The same happen to 'centralMeridian': the
relationship with the former 'lon_0' and 'vk' fields became more visible
after some algebraic work.
* Edited the parameter descriptors according the descriptions found on
www.remotesensing.org.
* Added 'equals' and 'hashCode' methods.
Some of the new formulas may seem quite different than the previous ones, but
actually they are really the same; I applied only algebraic operations (mostly
substitutions) that are mathematical identities. I hope that you don't mind
that
the formulas changed like that...
In practice algrabraic rearangement in a program may lead to rounding errors,
but in my tests I found (sometime) a difference only in the two last digits. Of
course the full test suite still pass (including "scripts/Krovak.txt").
Note: I have some hesitation about what the default values should be. A few
years ago we had default value like "scaleFactor=0.9999" for transverse
mercator
projection, on the basis that it was a commonly used value. But feedback from
users told us that such default values were misleading, that it was better to
keep default value to "natural" (or "neutral") numbers like 0 or 1. What do you
think?
Martin
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