| Re: Problems with converting map projection in ENVI [message #53140] |
Tue, 27 March 2007 13:14 |
Jean H.
Messages: 472
Registered: July 2006
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Senior Member |
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ke wrote:
> Hello,
>
> I have a file in ENVI's memory that is in one coordinate system
> (Washington State Plane North), and I would like to convert it to
> another coordinate system (geographic longitude / latitude). How can
> I do this in ENVI?
>
> I tried >Map >Convert Map Projection, but I must be doing something
> wrong in the 'Convert Map Projection Parameters' screen. Under
> 'Output Projection and Map Extent', it wants to know the coordinate of
> the upper left corner (I assume this is in the *new* projection
> system). I put in my best guess at what the upper left corner will be
> in lat/lon, and then OK, but the new image is all black. I think I am
> missing a step here - I want to convert the whole image, and don't
> know what the upper left coordinate will be, so why is ENVI asking for
> it?
>
> My original file is USGS digital orthoquad aerial photography, stored
> as a geotiff, in WA State Plane coordiates. How can I find the lat/
> lon coordiates that this image corresponds to?
>
> Thanks,
> Kathleen
Here comes my favorite answer: yes but no!
yes: the X and Y coordinates are for the upper-left (UL) corner in the
new projection
no: you don't gess it. When you open the >Map >Convert Map Projection,
you can see the current projection and the current UL coordinates. When
you change the projection, the UL coordinates are updated accordingly!
... so unless you want to shift (not even sure) your data, don't touch
this value! ... and voila!
Jean
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