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- From: e-sink@uiuc.edu (Eric W. Sink)
- Newsgroups: comp.graphics
- Subject: Contouring of curvilinear gridded data
- Message-ID: <BxLy4q.C7M@news.cso.uiuc.edu>
- Date: 12 Nov 92 14:41:12 GMT
- Article-I.D.: news.BxLy4q.C7M
- Sender: usenet@news.cso.uiuc.edu (Net Noise owner)
- Reply-To: e-sink@uiuc.edu
- Organization: University of Illinois at Urbana
- Lines: 43
- Originator: sink@ux2.cso.uiuc.edu
-
- OK, we've seen lots of messages about how to contour scatter data
- by gridding it first. My question now is about data that is
- already on a grid, but that grid is NOT rectilinear. Sometimes
- I've heard of this kind of grid being called a warped grid.
- Examples of commonly used warped grids include polar projections,
- and Mercator projections.
-
- The idea behind a warped grid is that each data point can have an
- arbitrary X,Y position. The X and Y values for adjacent data points
- on the grid should probably have some relationship, but they need not
- be rectilinear at all.
-
- Such a curvilinear data set could be represented by three matrices;
- one matrix for the data points themselves, and one for the X coordinates,
- and one for the Y.
-
- It would also be possible to represent this dataset as three columns,
- X, Y, and datavalues. This would eliminate the spatial ordering and
- neighbor information, reducing it to scatter data. However, then we
- could place the data on a uniform grid (assumedly with some loss of
- something) and contour it with normal methods.
-
- Now I turn this over, hoping some experts will expound on this.
- The above paragraphs give my [limited] understanding of this subject.
- What above is incorrect ? What else could be said ?
-
- What is gained by contouring on the actual warped grid, rather than
- making scatter data out of it, and contouring the uniformly gridded
- version ? Is this done very often ? Is the algorithm difficult ?
-
- Obviously, I'm not even sure what my question is. I guess I'm
- speculating that someone out there knows the answer anyway. :-)
-
- Thanks in advance!
-
-
-
-
- --
- Eric W. Sink, Spyglass | "You are the Pan."
- 1800 Woodfield Drive | - Rufio
- Savoy, IL 61826 |
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