[Requests] comments on Topic 21: Discrete Global Grid Systems Abstract Specification

Kevin Sahr sahrk at sou.edu
Thu Mar 9 13:33:59 EST 2017


Evaluator:

Kevin Sahr
Professor
Department of Computer Science
Southern Oregon University

Document:

Document Number: OGC 15-104r4
Name:Topic 21: Discrete Global Grid Systems Abstract Specification

Comments:

The document mentions hexagonal DGGS based on the ISEA projection and small
circle division methods. However, grids produced using either of these
methods will not pass the Test Suite given in Annex A.

Both approaches fail test A.1.8 because they do not produce grids with
cells that are all equal in area; both approaches produce DGGs with 12
cells that are 5/6 the area of all of the other cells in the DGG.

The ISEA approach also fails test A.1.6, because the projection distortion
produces cells that are not convex.
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