Wed, 2006-03-15 03:22 — ickers

Hi,

I've been studying the documents OGC 05-047r3 (GMLJP2), OGC 03-105r1 (GML 3.1) and grids.xsd and I've been unable to make sense of the meaning of the "offsetVector" element (a subelement of the RectifiedGrid element).

I know offsetVector is an instance of a gml:VectorType, which is itself essentially an instance of a gml:DirectPositionType (a list of doubles with optional SRS attribute). As best as I can tell, a pair of offsetVectors is supposed to provide the orientation of the grid axes in worldspace. Where I get lost is examples such as...

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...from OGC 05-047r3, p. 11 (PDF p.23). Would I be correct in saying that x-axis is parallel to the vector <1,2>, and the y-axis parallel to the vector <4,5>? If so, the x and y axes are not orthogonal (their dot product is non-zero). Is this allowable?

Also, does the magnitude of the x and y axis offsetVectors define the grid's scale? ie. does each 1

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## RectifiedGrid element question

Here is the response:

[i]...from OGC 05-047r3, p. 11 (PDF p.23). Would I be correct in saying that x-axis is parallel to the vector <1,2>, and the y-axis parallel to the vector <4,5>? If so, the x and y axes are not orthogonal (their dot product is non-zero). Is this allowable? [/i]

[David S. Burggraf] Yes, this was intended as is allowed

[i]Also, does the magnitude of the x and y axis offsetVectors define the grid's scale? ie. does each 1

## RectifiedGrid element question

Rhys

Let me check with the GMLJP2 editor.

Regards