Hi Reinoud-
makeVector makes grid relative vectors and you are looking for true
north vectors. Change your formula to be:
makeTrueVector( newName(a/a, "u") , newName(a/a, "v") )
and you should get the vectors pointing to 45N no matter what the
projection.
Don Murray
Reinoud Bokhorst wrote:
Hi,
I have a problem drawing vector fields when using my own formula and
custom lat/lon projections in IDV 2.7u2. It seems that the eastward
component is scaled incorrectly in my own projection, i.e. the eastward
component is scaled down such that my vectors always either point north-
or southward.
To isolate the problem I defined a formula to make vectors with equal
size u and v components (1,1):
makeVector( newName(a/a, "u") , newName(a/a, "v") )
I plotted this using 3 lat/lon projections (see attached image, zoomed
in on Gulf of Aden):
- predefined 'world'
- predefined 'africa'
- custom, my own region defined using projection manager
In all 3 cases the vectors point in a different direction (they tend to
rotate to the North). Only in the 'world' projection, the vectors seem
correct. What's wrong?
(I have posted this question in another thread some weeks ago but
haven't received an answer, apologize if I am being too impatient).
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Don Murray UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000
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