Zitat von Martin Desruisseaux <[EMAIL PROTECTED]>:
> "In this International Standard, coverage is a subtype of feature.
> A coverage is a feature that has multiple values for each attribute
> type, where each direct position within the geometric representation
> of the feature has a single value for each attribute type."
>
> The first sentence is easy to understand, but I admit that I have a lot
> of trouble to understand what the second sentence means.
After having read the sentence several times I believe I know what they try to
say:
As we know one coverage can contain multiple attributes (f.e. multiple spectral
bands in a remote sensing image).
The second part of the sentence says that (of course) each pixel has one value
for each of the attributes (bands), but since the whole coverage is a
collection of all pixels, the coverage itself cannot have just ONE value for
each attribute, but has "all possible values" as the value for the respective
attribute (band).
Example:
- Pixel x of band 3 in a Landsat TM image has DN value 50
- But in the Coverage, that contains pixel x the band 3 has the values {0, 1,
.., 255}
Again, this is what I believe they want to express. I am not saying this approch
looks useful for me.
However independent from this I can see that representing a coverage as a
feature has some positive aspects too: You could, f.e. create a style that just
draws the whole coverage outline or draws the coverage as one big polygon (for a
scene overview map for example).
Hm. There are more consequences of this decision than I thought.
Matthias Basler
[EMAIL PROTECTED]
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