Comments on: Use makehgtform for 3-D rotation http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/ Steve Eddins manages the Image & Geospatial development team at <a href="http://www.mathworks.com/">The MathWorks</a> and coauthored <a href="http://www.mathworks.com/support/books/book5291.html?category=-1&language=-1">Digital Image Processing Using MATLAB</a>. He writes here about image processing concepts, algorithm implementations, and MATLAB.<br><br><img> Mon, 23 Nov 2009 00:54:29 +0000 http://wordpress.org/?v=2.3.1 By: Qi Chen http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4925 Qi Chen Mon, 25 Sep 2006 22:58:19 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4925 Thanks a lot. Rob. Thanks a lot. Rob.

]]> By: Rob Comer http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4849 Rob Comer Fri, 22 Sep 2006 19:57:17 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4849 Qi Chen - You are correct, you can't use reprojection alone to move data from one reference ellipsoid to another. What you need is a <em>datum conversion</em>. In fact, just knowing two numbers, a latitude and a longitude, doesn't tell you where something is. You also need to know which datum (reference system) the numbers refer to. We don't have a Mapping Toolbox function for datum conversion, but there are some free resources that you can find by searching the Internet. Qi Chen - You are correct, you can’t use reprojection alone to move data from one reference ellipsoid to another. What you need is a datum conversion. In fact, just knowing two numbers, a latitude and a longitude, doesn’t tell you where something is. You also need to know which datum (reference system) the numbers refer to. We don’t have a Mapping Toolbox function for datum conversion, but there are some free resources that you can find by searching the Internet.

]]> By: Qi Chen http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4668 Qi Chen Tue, 19 Sep 2006 00:55:06 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4668 Steve, thank you very much. I have been reading this demo and thinking in the same direction as you suggested. Another question I have is: if two projections (UTM and Alberts) have different ellipsoids, the geographic coordinates would be different even when they are converted from UTM and Alberts coordinates with minvtran. Is there a function that can convert the geographic coordinates between different ellipsoids? Steve, thank you very much. I have been reading this demo and thinking in the same direction as you suggested. Another question I have is: if two projections (UTM and Alberts) have different ellipsoids, the geographic coordinates would be different even when they are converted from UTM and Alberts coordinates with minvtran. Is there a function that can convert the geographic coordinates between different ellipsoids?

]]> By: Steve http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4661 Steve Mon, 18 Sep 2006 13:19:12 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4661 Qi Chen - We don't have a function that performs raster reprojection end-to-end. A knowledgeable person could combine functions such as tformarray or interp2 with Mapping Toolbox functions mfwdtran and minvtran to write a reprojection function. There's a Mapping Toolbox demo about unprojecting a DEM that shows some of the steps for reprojecting a grid. The demo is called <a href="http://www.mathworks.com/products/demos/shipping/map/mapexunprojectdem.html?product=MG" rel="nofollow">"Un-Projecting a Digital Elevation Model (DEM)."</a> Qi Chen - We don’t have a function that performs raster reprojection end-to-end. A knowledgeable person could combine functions such as tformarray or interp2 with Mapping Toolbox functions mfwdtran and minvtran to write a reprojection function. There’s a Mapping Toolbox demo about unprojecting a DEM that shows some of the steps for reprojecting a grid. The demo is called “Un-Projecting a Digital Elevation Model (DEM).”

]]> By: Qi Chen http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4614 Qi Chen Sun, 17 Sep 2006 01:04:35 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4614 hi, Steve I have a question that needs your kind help. I have two images/grids with different projections (UTM and Alberts) for the same area. Do you have any ideas on how to convert any image from one projection to another (say, Alberts -> UTM). I checked the Mapping Toolbox and Image processing toolbox and haven't found a solution to this problem. Any of your hints will be highly appreciated! Sincerely, Qi hi, Steve

I have a question that needs your kind help. I have two images/grids with different projections (UTM and Alberts) for the same area. Do you have any ideas on how to convert any image from one projection to another (say, Alberts -> UTM).
I checked the Mapping Toolbox and Image processing toolbox and haven’t found a solution to this problem. Any of your hints will be highly appreciated!

Sincerely,
Qi

]]> By: Steve http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4579 Steve Fri, 15 Sep 2006 11:34:56 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4579 Shanika - use makecform and applycform in the Image Processing Toolbox. There's an example in one of my blog postings from June. Shanika - use makecform and applycform in the Image Processing Toolbox. There’s an example in one of my blog postings from June.

]]> By: Shanika http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4578 Shanika Fri, 15 Sep 2006 11:27:35 +0000 http://blogs.mathworks.com/steve/2006/09/07/use-makehgtform-for-3-d-rotation/#comment-4578 Steve, cool artwork you've created there. I got a question but its nothing to do with 3-D stuff. How can I convert RGB values to L*a*b values in MATLAB? I have uploaded a digital image to MATLAB workspace and wanting to get Lab values for each pixel. Please give me an idea...I tried the MATLAB help also. cheers Steve, cool artwork you’ve created there. I got a question but its nothing to do with 3-D stuff. How can I convert RGB values to L*a*b values in MATLAB? I have uploaded a digital image to MATLAB workspace and wanting to get Lab values for each pixel. Please give me an idea…I tried the MATLAB help also. cheers

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