Anderw, I agree they are the same, but the developers appear to live in
different worlds!
The imaging programs (eg photoshop) focus on how the grid of values renders
on the screen, not what the values mean. Formats are optimised to represent
colours or grey scales.
With grids (eg a terrain grid) we are usually more interested in the
underlying grid values. So we put up with the inefficencies of working with
real numbers and characters as the "grid" values.
I think it is all about mind set. Yes, Image enhancement and grid
manipulation programs both work on rectangular arrays of values, but they
present different tools to reflect the end user focus and they optimise
their storage formats to different ends.
But with Landsat Imagery we like to use imaging tools (like contrast
stretch and edge enhncement) to change the way the image renders, and
sometimes we work with the raw grid values (eg in grid classificaiton). So
we get caught in deep space between the two worlds.
Vertical Mapper comes from a grid manipulation background. But their
coloriser maps ranges of real values to colours so we can present the grid
on the screen as an image.
Now do we call them grids, images or rasters? We can argue that one for
hours..
But some translators would be nice.....
... Ken Moule, Exa-Min
At 06:51 07/12/99 +1000, you wrote:
>I agree with Charles. The only difference between an image and a grid in my
>view is that an image is usually constructed of a finer mesh of points
>(pixels), and then maybe not in the case of some LANDSAT imagery where the
>ground resolution is about 30m, and there are multiple instead of single z
>values for each point in the image (as opposed to a single z value in a
>grid). Effectively, grids are the representations of a single "channel" or
>"band" of data forming an image.
>
>
>
>Andrew Waltho
>Brisbane, Australia
>
>e-mail: [EMAIL PROTECTED]
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
>Behalf Of Charles Huyck
>Sent: Tuesday, 7 December 1999 3:00
>To: [EMAIL PROTECTED]
>Subject: MI: Image VS GRID?
>
>What is the difference between an image and a Grid? One is derived and one
>is imported? Aren't they both just 2D (or more) arrays of numbers? Color
>values reference the object. You can analyze these numbers to extract and
>classify the object, like on the X-files last night when the FBI agent used
>"SKAG" to classify a surveillance video still and it turned out to be the
>exact colors of the some guy's letter jacket.
>
>I guess ESRI is doing away with this weird GRID vs image thing. I never
>understood the difference anyway.
>
>
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