I think that many MI users in this list are using VM and therefore their knowledge of "What can I do with MIG grid" is limited ONLY to GridEngine. This is because of MapInfo's policy. From version 5.5, there has been no improvement in MapInfo's grid engine, neither in functions on grid. Therefore users lost interest in this format.
Some changes came into being after Grid Analyser appeared in the 2000. Users from the whole world have started to use it and suggested new ideas and improvements. I decided to improve Grid Analyser taking into account their suggestions. And the result?? Now, Grid Analyser's and Vertical Mapper's possibilities (applicability) are equal, if not Grid Analyser's are richer, but users interest decreases. Different trend can be seen only in small countries were companies are NOT so wealthy and their employees are looking for the cheapest solution with the same level of accuracy and applicability.
By my opinion, everything what you can do with VM grid (in VM environment) can be done with MI grid (in GA environment) too. Furthermore, some analyses can be performed only in GA environment (watershed analysis, detailed statistical information, point density estimation, spatial data estimation, distance and proximity grid and much, much more)!!!
Some problems appear when working with huge grids (more than 5000x5000, it means 25 000 000 grid cells). I think, it isn't a problem with MIG, but with computer's memory.
And now some words to your problem. I had tried to find solution but without success. Here is a sum:
1st problem
The first strange thing is that after adjusting the cell size in the Settings window of the Grid requester, the grid size displayed is one unit smaller (in width as well as in height) than would be necessary to cover the entire surface.
I created a testing set of irregularly distributed points. When I used Themetic mapping feature, the projected grid size was 239x200, in the case of GA 238x200, with same grid cell size of 0.0014 mi. After I changed the window units from mi to m, for grid cell size of 2.5m the Thematic mapping function shows 215x180 and GA reports 214x180.
My conclusion is that the problem is in calculation of grid dimension in MI. So do NOT rely on this information. Use GA or Grid tools with your grid and see what dimension is reported - I am sure it is correct. Compare it with the dimension showed in the Thematic dialog of MI. Can you see the differences?
2nd problem
The next strange thing is revealed by some dll calls to the MIG file for info (MiGrid.DLL) These calls return the number of cells as been 1 more than the required number, but with a relatively exact set of coordinates for the
region covered. Some tests I ran with an oldie of mine (InfoExMig) and particularly the conversion of the MIG file to a standard MI region TAB, confirm that even if MI tells you that the grid should be say 121x115 cells (settings) while it should be theoretically 122x116, it generates an image of 123x117 cells that do not measure the set value of 1 (in this example) but of 122/123 in width and 116/117 in height.
I do NOT think that the problem is in calling function from MiGrid.dll. By my opinion, the problem is inside in the code where the grid process is started and where the resulting dimension is determined. I don't have any problems calling MiGrid.dll.
The conludsion is: do not use original MI thematic grid function if you need to know the exact dimension of the grid. I recommend you to use Grid Analyser if you need to know exact dimension of the grid (through GA you can control the dimension of the grid by grid cell size as well as by the minimum border coordinates of interpolated points).
Best regards
Stefan Majtan
************************************************************************** TERRIS GIS Applications Development Grid Analyser - raster GIS for native MapInfo grid
Pod záhradkami 24 909 01 Skalica SLOVAKIA http://www.terris.sk **************************************************************************
On Wed, 3 Mar 2004 07:50:44 -0500, Jacques Paris <[EMAIL PROTECTED]> wrote:
I put SUM in the subject but it is a misnomer because SUM = 0 (ziltch)
As I had already touched on the subject at least 2 years back and got the same (lack of) reaction I have to choose between two possibilities
1 - that whatever I say is never challenged because I know the subject and
nothing has to be added- and that I do not accept
2 - that the MI adventure in GRID-mig files is seen as very unimportant by
MI users because MI did not put into it enough energy to make it an
interesting tool - and that, I am more inclined to accept.
There are those who would say "But why worry? VM is there" They should
however be very concerned about what they will get. In fact what they are
already getting (beside a hefty bill, compared to a free GRID) is as
unreliable (if differently) relatively to grid registration as I have noted
for a MIG. That we are in both cases dealing with "images" is not a reason
to wave off their reliable registration
I am willing to drop the issue but not without warning you a last time about
those unacceptable poor performances
Jacques Paris e-mail [EMAIL PROTECTED] MapBasic-MapInfo support http://www.paris-pc-gis.com
--------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 10680
__________ Informacia od NOD32 1.639 (20040228) __________
Tato sprava bola preverena antivirusovym systemom NOD32. http://www.eset.sk
--
--------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 10685
