From: Andrea A. <aa...@li...> - 2003-02-03 17:05:19
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Martin Desruisseaux wrote: > Ian Turton wrote: > >> No, I think a layer is a collection of features with styles. A feature >> is a single geographic object with attributes. > > > If we have a layer of "wind stress field" made of thousand of wind > vectors, is each vector a feature? It is doable (we don't have to create > thousand of Feature; we could wrap internal data in a Feature object > upon request only) - I'm just asking... (I was use to see the whole > vector field as a feature. If a have a "marine current field", it would > be an other feature/layer, etc.) > Well, it depends... I agree with Ian that these seems more a grid coverage than a feature (fields instead of objects). Are these vector regularly spaced? If so, they could be represented by a couple of grid coverages togheter (magnitude in one converage, an angle representing direction and orientation in another), but if not they they could be modelled by a point layer (so, features) with a couple of attribute for each feature, and a special renderer that allows for "arrows" to be drawn according to the associated attribute data. I think that there was some old, DOS based raster gis that did exactly this, allowed the user to represent wind fields and the like with a couple of grid coverages and then was able to represent them with arrows... Best regards Andrea Aime |