some of my naive understanding of the data model: >First question: how are the different type determinations for geometry objects saved in GRASS? What >makes a boundary a boundary and separates it from a line? The same for points and centroids.
taken from https://grass.osgeo.org/grass70/manuals/vectorintro.html - point: a point; - line: a directed sequence of connected vertices with two endpoints called nodes; - boundary: the border line to describe an area; - centroid: a point within a closed ring of boundaries; - area: the topological composition of a closed ring of boundaries and a centroid; an area is build upon boundaries and centroid; e.g. change line to boundaries and point to centroid and build and area >Second: Up to now, I was not able to understand the concept of layers in GRASS. I've read a lot of >explanations, most of them telling that a layer is a set of category values making up a different view to >the underlying geometry objects. Using layers, the geometries can be aggregated or individually marked in >a different, yet parallel manner at the same time. > >But everything described in the manual or Wiki seems to me like one can do this using different attribute >columns as well. just think of a line representing a road: e.g. layer 1 represents the road type (e.g. small road ... highway), layer 2 holds the information if it's allowed for bicycles; with the layer concept you doesn't need an attribute table (but you can have also attribute tables in every layer) to hold different characteristics of e.g. a line, boundary, point etc. but obviously there is some overlapping between the layer and/or attribute concept... ----- best regards Helmut -- View this message in context: http://osgeo-org.1560.x6.nabble.com/Newbie-questions-about-GRASS-data-model-details-tp5257044p5257056.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
