>Does anyone have experience of using either large grid files or tiled grid
>files to represent, for example, elevation data?
We have some.
>We're trying to determine the best way to distribute DEM data for use by
>MapInfo Professional (without add-in's). Options we've considered are:
(1)
>points (2) square cells as regions and (3) .mig files. Given around 10
>million readings, option 1 would be bulky and option 2 even more so!
>Specific questions on .mig files- (1) what is the size limit? (2) is the
>limit related to the IDW algorithm? (3) are there alternative algorithms?
>(4) has anyone written a .mig loader, say from a point file?
1. Based on the definition of these functions from the API, the size limit
appears to be about 2,147,483,648 x 2,147,483,648, but I'm sure practical
limitations become apparent long before that.
BOOL GRIDENGFUNCTION GE_GetContinuousValue(GE_HGRID hGrid,
long lCol, long lRow, double *pdValue, unsigned char *puchIsNull);
BOOL GRIDENGFUNCTION GE_GetDimensions(GE_HGRID hGrid, long *plWidth,
long *plHeight);
BOOL GRIDENGFUNCTION GE_WriteContinuousValue(GE_HGRID hGrid,
long lCol, long lRow, double dValue);
2. No, the IDW algorithm is just one way to create a grid file.
3. I know that ESTI-Map in Moscow has written a TIN-based interpolator,
and Mercator Geosystems has others.
4. MapInfo Professional 5.5 (and now 6.0) includes a DEM2GRID utility.
The complete API for the Grid Engine is available upon request.
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