Re: Resampling from lat/lon to projection

  • To: Kjell Røang <kjell@xxxxxx>
  • Subject: Re: Resampling from lat/lon to projection
  • From: Tom Whittaker <tomw@xxxxxxxxxxxxx>
  • Date: Thu, 20 Mar 2003 08:23:17 -0600

The reason I want to do the transformations (projections) ourself, is to be
able to support more output projections (to the user). We will probably use
the projection package in geotools. The interpolation we gladly let VisAd

If 'geotools' can convert an array of points from one projection to another, you could create a VisAD CoordinateSystem that simply interfaces with that.

The JGrib package now handles Lambert and Stereographics grids and convert
it to lat/long. Probably we will be able to support more coordinate systems
in the future. (JGrib is an open source project at ).

I would like to continue to expand the projections that are supported in GRIBCooridnateSystem, especially when it comes to the "grid number" ones - right now it only knows about 201,202,203,211,212,215,236.

Another question related to interpolation: If one wants to interpolate to a
pixel sized grid, is it more efficient to first interpolate to a "coarse"
rectangular grid (both geometry and topology) and from there interpolate to
the pixel sized grid?

If the reason you want to interpolate to a "pixel sized grid" is to be able to show a grid as an image, then I would suggest just letting VisAD do the display using your coarse grid. If there is some other reason, I'd be curious to know...?

I would avoid a double interpolation for the reason that you would be essentially filtering your data twice and might introduce side effects that are unpleasant. It certainly could be more computationally efficient to initially interpolate to every N-th point in your "pixel grid" and then do a linear interpolation in between these points...but it does beg the question about why you'd like to use a 'pixel sized grid' in the first place.


Tom Whittaker (tomw@xxxxxxxxxxxxx)
University of Wisconsin-Madison
Space Science and Engineering Center
Cooperative Institute for Meteorological Satellite Studies
Phone/VoiceMail: 608.262.2759

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