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03/11/14 03:37 AM
Re: Map projections [re: fmoretzsohn]Report this article as Inappropriate to us !!!Login to Reply

Two more comments about the equal-area map for the Indo-Pacific region:

1. In my most recent post, I questioned whether "Local Hammer" retains Hammer's equal-area property. Of course it does. Local Hammer just amounts to using the central part of Hammer, for a region smaller than the entire Earth.

As I said, the only difference is that instead of always using a Hammer expansion factor (denoted by "F" in my previous posts here), you'd choose F to match the shape of the region being mapped.

2. By tropical Indo-Pacific, I assume that you mean the tropical Pacific, Indonesia region, and Indian Ocean. A few comments:

1. That region is so long and skinny that, even though Local Hammer might be better than Cylindrical Equal Area (CEA), CEA would be nearly as good, and so you might as well continue to use CEA for that mapping project.

In fact, that seems to remain true even if, by tropical Indo-Pacific, you're referring only to the tropical part of the Pacific, and the Indonesia region (without the Indian Ocean).

2. Of course the mapping of only the tropical regions makes the map long and skinny. Additionally, it greatly simplifies things, with CEA, because you'd be using CEA in its standard, equatorial aspect.

Of course the same would be true if you used Local Hammer. But CEA is simpler, and, as you've found, CEA is already available, ready-made.

3. So, bottom-line:

Because of the long skinny shape of the region that you're mapping, I recommend Cylindrical Equal Area (CEA), due to its low distortion for such a shapeed region, and due to its simplicity and ready-made availability.  ...even if, strictly-speaking, Local Hammer could somewhat reduce the maximum shape distortion (the shape distortion of a CEA map of such a long and skinny region would be slight anyway).

Michael Ossipoff










Entire thread
SubjectPosted byPosted on
*Map projections fmoretzsohn   03/09/04 02:08 PM
.*Re: Map projections MichaelOssipoff   03/11/14 03:37 AM
.*Re: Map projections MichaelOssipoff   03/10/14 01:53 PM
.*Re: Map projections MichaelOssipoff   03/10/14 12:52 PM
.*Re: Map projections scrabblehack   05/31/06 07:49 AM
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