Re: [OpenMap Users] DTED data and projections

Hi Roy,

On Apr 15, 2004, at 9:04 AM, Roy Newton wrote:

> Hi everyone...
>  
> Is there any way to load DTED data without setting the map projection
> to either LLXY or CADRG?  I would like to use the default projection
> (Mercator?) if possible.
>  

Load? Sure, use the DTEDFrameCache by adding it to the
openmap.components property of the openmap.properties file. That will
allow access to the DTED data regardless of projection.

Displaying the data in a different projection is a different matter.
You could modify the DTEDLayer code to ignore the requirement for an
EqualArc projection, but the display of the data would be inaccurate
and probably kind of funky. Depending on the scales you work with,
though, the effect might not be noticeable to the casual observer.

There's a new version of DTED handling code checked into the CVS
repository for the next release that moves toward handing DTED data in
OMGrids, and you could write an OMGridGenerator that creates images
from the DTED data for different projections. There are new
OMGridGenerators that create images for EqualArc projections, you would
just extend those to use the projection to find the lat/lon (and then
the data values) for different pixels of the image representing the
data, and color the image pixels accordingly. It's kind of the same
thing the com.bbn.openmap.plugin.earthImage.EarthImagePlugIn does,
creating an image that fits any projection from a source image where
you know the source's lat/lon<-> pixel values.

Hope this helps,

Don

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