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We use a semitransparent grid layer (.mig file) to show 'hotspot' intensity in MapBasic (MapInfo. Because the grid is just a rectangle, this looks ugly. See for instance: http://download.sentient.nl/files/Images/20100809Hotspot.png.

Now MapInfo allows grid cells to be invisible (NULL), which would result in round-like hotspot regions.
But we would prefer to extend the grid. Of course we could just add extra rows and columns, but that would require a lot of extra memory. And it would still show a boundary at some zoom level.

Is it possible to infinitely extend a grid layer with a constant value?

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Can I ask what you used to create the hotspot? –  Nathan W Aug 9 '10 at 10:42
    
I'm afraid it's a proprietary component, called DD2M. –  Michel de Ruiter Aug 10 '10 at 20:46
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3 Answers 3

The grid is created on the extents of the thematic data (selection or table). Therefore you could add two points of dummy data (top left and bottom right) of the extents of the projection.

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This might be the answer we are looking for, but I don't know how to do this. Can you elaborate? –  Michel de Ruiter Jun 25 '12 at 15:29
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up vote 0 down vote accepted

I dived a bit more into it.

We use MIGrid.dll. I found one (old) reference.

A grid is mapped to a rectangular region (GE_GRID_INFO stuct). Every cell has equal size. So I'm afraid it's just impossible with grids.

If anyone knows of a workable alternative, using MapInfo...

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Are you sure there's much of a performance hit for extending the extent? In ESRI software, a grid with integer values is compressed on disk and by default the NoData values are not drawn. Perhaps MapInfo has something like this too? –  whuber Mar 10 '11 at 2:08
    
I'm afraid not. –  Michel de Ruiter Mar 16 '11 at 14:24
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http://acidmaps.org

the good thing is it integrates with Geoserver. Geoserver is the GIS server of choice at vtsPN. Since I am involved with Sherpa now, I might be able to pull a few strings ;-)

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I asked about MapInfo specificially: moving to a different GIS system is not really an option. But thanks for the reference. –  Michel de Ruiter Apr 1 '11 at 9:51
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