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Re: Map Projections with User Defined Ellipsoids (Mars) [message #45553] Wed, 21 September 2005 11:40
James Kuyper is currently offline  James Kuyper
Messages: 425
Registered: March 2000
Senior Member
Ben Tupper wrote:
...
> I don't see that i can adjust the semiXXX_axes. Are you sure that you
> had imap set to sinusoidal projection? Those change only when I change
> the datum in the projection dialog.

If you select "user defined" as the datum, you're then allowed to
specify the semiXXX_axis values.
Re: Map Projections with User Defined Ellipsoids (Mars) [message #45555 is a reply to message #45553] Wed, 21 September 2005 10:35 Go to previous message
btt is currently offline  btt
Messages: 345
Registered: December 2000
Senior Member
Sebastian wrote:
> Hello list,
>
> I'm suffering about the fact that the adjustable parameters of the
> IMAP's Projections differ from the ones of the MAP_PROJ_* routines.
>
> My need is to display images of mars with a known projection
> (sinusoidal) with the apropriate radii of mars (~ 3396 km).
>
> IDL's manuals say that the parameters SEMIMAJOR_AXIS and SEMIMINOR_AXIS
> are not allowed for MAP_PROJ's sinusoidal projection.
>
> But if I open the image in IMAP, the fields for filling in the ellipsoid
> axes can be used.
>
> As far as I know, IMAP is using the routine MAP_IMAGE for this purpose.
> My IDL knowledge is too limited to understand what is going on in the
> IMAP code.
>
> Has anybody experiences about user defined ellipsoids? Thanks for any help!

Hi,

When i do the following...

imap, map_projection = 'sinusoidal'

I don't see that i can adjust the semiXXX_axes. Are you sure that you
had imap set to sinusoidal projection? Those change only when I change
the datum in the projection dialog. I'm no map expert - but I think it
is the datum you specify in order to control the axes.

Cheers,
Ben
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