gabor@xxxxxxxxxxxxxxxxxxxxxx writes: > > I suggest we > approach the question carefully and look around before fixing this > problem locally. Quick fire-fighting work always turns out to be > painful. This is certainly my opinion also. I just thought that I would throw out a couple of examples to "stir the pot". < Text deleted > > Harry Jentner said he would not like to have assumptions. Me either. > But netCDF already does have one. It is assumed all data are given > over rectangular grid. I think that netCDF does not require this assumption to be made. It is just more intuitive for storing rectangular or, more generally, quadrilateral grids, without introducing one's own conventions. (Note: I stick to the 2-d grid analogy for the rest of this post. The arguments can be extended to 3 or more dimensions, but I don't know the words for "equivalent of quadrilateral" in 3 or more dimensions.) There seem to be no assumptions regarding grid shape. There are also seem to be no conventions regarding grid shape. I think, however, that the issue of storing non-quadrilateral grids is a more difficult issue to address than the regularly-spaced-coordinate issue. In fact, it is, in a sense, the opposite problem. For regularly-spaced coordinates, one can reduce the information stored in a netCDF file relative to the "intuitive" method of storing a 1-d array for each coordinate, and still can reproduce the grid. For non-quadrilateral grids or even quadrilateral-but-not-rectangular grids, one must increase the amount of information stored in the netCDF file in order to reproduce the grid. For non-quadrilateral grids, information about what nodes are connected must be stored. For curvilinear grids, the coordinate arrays must have more than one dimension. < Text deleted > > What Harry suggests is a way to indicate if the given grid in one > dimension (that may happen to be TIME) is equally spaced. But what > about the other functions? What if a dimension is logarithmical or > derived with any other function? This is a good point. I forgot about grids that are stretched according to a function. > And further, data points are not necessarily given over a > rectangular grid. The grid could be just genarally quadrilateral, or > may be triangular as often is. Or what about a general polygonal grid? I do not know much about non-rectangular grids, but I have heard that the HDF Vset has a mechanism for storing them. I have also heard that the DX format for IBM's Data Explorer product has provisions for storing non-rectangular grids (I think that Lloyd Treinish, a frequent contributor to netcdfgroup is helping to design this format.). Does anyone know more about these? > Will we introduce more and more assumptions? What we need is to think > over the whole issue, introduce a CONCEPT instead of AD-HOC attribute > or whatever solutions. You don't have to YELL. I agree with you. I also think that the netcdfgroup is an appropriate forum for discussing these ideas. -- Harry L. Jenter hjenter@xxxxxxxxxxxxxxxxxx U.S. Geological Survey COM: (703) 648-5916 FTS: 959-5916 Mailstop 430, National Center "Sometimes you're the bug. Reston, Virginia 22092 Sometimes you're the windshield."