It sounds like you are making the distinction that a Grid file can have
character attributes while an image can not. Well, the character
attributes in a "Grid" are kept in a separate table and linked anyway, so
they should compress the same. If you compress numeric data, you stand to
loose just as much as when you compress character data (as in the case of
townships). I don't think things like "Mr. SID" are kind enough to take
that into account, however. That may have changed since I last talked to
them.
I think one advantage to what people call "Images" is that they generally
accommodate irregular pixels. People usually use square GRIDs, but I don't
know about all packages. Also, people sometimes manipulate a "GRID" file
to contain more than one attribute field, but with imagery, you just store
it in separate bands. I find the multiple columns data model more
intuitive for database work.
But concerning MapInfo, can you even translate an image to a Grid file? Has
anyone used that API thing they distribute to perform calculations on the
underlying data, then post it back? Is it easy to use? I have not had the
time to sit down and figure it out.
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