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I'm writing Shapefiles through Fortran with success, writing points, lines, and polygons. The next step in this project (separate from the previous step) is to write grids such that each cell can be coloured to correspond to a value/field. Seems to me that a raster would do this perfectly, if my data was simply rectilinear (the Esri ASCII raster would be fitting). However, I'm working with curvilinear grids, and each cell does not have the same size as the next. Additionally, the grid might be rotated, depending on the location. For example, say I have a river that doesn't necessarily run just North-South. The grid is created based on the river and is rotated to match the river. Parts of the river that are especially twisty or have a varying river bed will have smaller or more cells to compensate. And then the grid would be coloured accordingly, depending on temperature, or salinity, or whatever. I'd be able to do this easily as well in Matlab or something but the client specifically wants to be able to view everything in ArcGIS 10.1/10.2.

I'm not sure how to go about this, I've tried searching this site and the internet, using combinations of words like 'non-uniform', 'curvilinear', 'cell sizes', etc. but I haven't managed to find what I need. I've attached an example image of what I'm working with and what I'm looking for. Notice that the cells are not all the same size and are also at an angle.

I would have added tags like 'non-uniform grid' or 'curvilinear' but I can't yet, so hopefully this sentence helps with searchability.

closed as too broad by Vince, whyzar, xunilk, tinlyx, BERA Mar 1 '18 at 6:48

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • Targeting retired software with new development is very strange, as is new development in FORTRAN. The irony is that F77 was the development language for Arc/Info (from PIOS through 5.0), but that introduction of shapefiles and rasters were both done using 'C' in the early 90's, so not even Esri has used FORTRAN for either. IIRC, initial Grid libraries were only square pixels, and transitioning to TIFF as the nominal raster format permitted rectangular pixels, but Esri has never supported curvlinear rasters. – Vince Feb 28 '18 at 22:07
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GIS software doesn't handle curvilinear grids.

You can convert it to a simple raster, with uniform cell sizes, or maybe to a vector.

The only way to do the conversion from curvilinear to regular grid is handling the data with Python. You may be able to get cdo to do it automatically, but it doesn't work all the time.

  • Not to question your answer, but is it written or documented anywhere that curvilinear is not supported? – stackman Feb 28 '18 at 21:44
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    This Esri introduction explains that rasters are rectilinear. It's not common to define something by what it isn't, especially in introductory materials – Vince Feb 28 '18 at 22:35
  • Sorry, @stackman, but I did search for it but can't find reference to curvilinear grids in relation to QGIS. I'm commenting from my experience, and I've worked with curvilinear grids in NetCDF files previously. It's a specific scientific way of working, and is rather bespoke. As such, it's not supported in most/any GIS desktop packages I am aware of. I'm happy to be proven wrong, but this is my experience. – Alex Leith Feb 28 '18 at 23:00
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I think you are wrong calling it raster, grid or cell, the basic idea of cells is their regularity in any way, size and/or shape.

I also think that that raster are the best data type to handle spatial data that is valid for a surface. When a curvilinear feature is needed, a suficient resolution is adopted in order to cope with the discretization. For instance, a river is better represented by pixels a couple of time smaller than the river width.

If raster do not work for your need, then you are after a Tesselation.

One of the most documented tessellation in GIS is the Voronoi.

  • Fair enough, I couldn't think what else to call it and the raster/grid was the basic form I was after. I've thought of that and that was my plan B but I was hoping against it, but perhaps I'll have to give that a shot. Thanks. Any ideas on getting started with tesselation? I'm looking into maybe hexagons with MMQGIS but any advice is appreciated. – stackman Feb 28 '18 at 21:53
  • Start with Verenoi – Marco Feb 28 '18 at 21:59

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