thanx for your comments Michael and Martin. now my points below
Michaël Michaud schrieb: > Hi Uwe, > > Classifying plugins under Tools menu is really a hard job and some > inconsistencies may come from a lack of coordination among developpers. > I'll try to help with my limited knowledge of those functions > >> 1. What is the different between Tools>Analysis and Tools>Queries? >> >> > I think queries never modify features, only select some of them. excactly. the primary idea is to select/extract features from an existing set. > >> 2. Buffer is (one time) under Tools>Generate but Union (one Layer) is >> under Tools>Analysis? >> >> > IMHO, this is not very consistent mhm.. the idea was to put in "Generate" tools that generate new features using (pure??) geometry operations. Here, one should only optain geometries - i.e. features without attributes. The analysis section should involve more complex functions that generate new and modify features which also include attribute operations/analysis. SIGLE had actually a nice approach with a menu for "one-layer" and "two-layer" ops. But this may also lead to some duplications. on the D-P question had Martin already a good answer. (Note, another term for the Douglas Poiker (or Peucker) Simplification would be Point Removal, but D-P specifies the algorithm. Other point removal algorithms exists as well such as the Visvalingam algorithm or Bend-Simplfy) [wow.. when google-ing for bend-simplify i found this presentation on GIS for military analysis... http://www.dodccrp.org/events/12th_ICCRTS/CD/html/presentations/006.pdf ..scarry.. ] stefan > >> 3. Is there a reason why we have different notations (for example): >> Source, source layer, Layer A, Layer, Source Layer? >> >> > I saw that where A and B are used, they are referred in the explanation > panel "select A.*, B.*..." which may be the reason. There may be some > situations where layers have symmetric roles (like overlays), and others > where a layer has a special role (source, target, reference), like > attribute transfer. > >> 4. What is "Simplify D - P"? >> >> > Simplify Douglas Peucker : a simplification algorithm (Stefan can > surely explain that better than I) > >> 5. What is "Simplify (preserve topology)"? >> >> > Simplify (preserve topology), applied to a network, preserve connections > between linestrings (maybe Simplify D-P don't, I did not try). > Sadly, topology is not preserved for a planar graph represented as > polygons touching each others > >> 6. Thank you for your help! >> >> >> >> 1 = Tools>Analysis>Geometry Functions (Source, Function, Parameter, Mask) >> 2 = Tools>Analysis>Join Attributes Spatially (target layer, source >> layer, ...) >> 3 = Tools>Analysis>Overlay >> 4 = Tools>Analysis>Spatial Join of Geometries (Layer A, Relation, >> Parameter, Layer B) >> 5 = Tools>Analysis>Union >> 6 = Tools>Analysis>Union by Attribute Value >> 7 = Tools>Generate>Buffer >> 8 = Tools>Generate>Convex Hull >> 9 = Tools>Generate>Convex Hull on Layer >> 10 = Tools>Generate>Create Thiessen Polygons >> 11 = Tools>Queries>Simple Query (Layer, Operator, Value) >> 12 = Tools>Queries>Spatial Query (Source Layer, Relation, Mask Layer, >> Parameter) >> >> >> > Hey, seems there is a lot of redundancy :-( > It will be hard to clean up as many functions are close to each others, > but not strictly the same. > May be a solution could be to propose some of them for removal (or to be > packaged in a special extension) and vote. > Anyway, you did an excellent job, and I'll try to spend a little more > time to see the difference between all those function and to tell which > one are better for me. > > Regards > > Michael > >> Boundary 1 >> Buffer 1, 7 : first can >> Centroid of Source 1 >> Contains 2, 4, 11, 12 >> Convex Hull 1, 8, 9 >> Covers 4, 12 >> Crosses 4, 11, 12 >> Difference A -- B 1 >> Difference B -- A 1 >> Disjoint 4, 12 >> Envelope 1 >> Equals 4, 12 >> Is Covered by 2, 4, 12 >> Is Disjoint 11 >> Is Includet in 11 >> Is Within Distance 4, 11, 12 >> Interior Point 1 >> Intersects 1, 2, 3, 4, 11, 12 >> Line Merge 1 >> Line Sequence 1 >> Overlaps 4, 11, 12 >> Polygonize 1 >> Reverse Line Direction 1 >> Simplify D -- P 1 >> Simplify (preserve topology) 1 >> Similar 4, 12 >> Symmetric Difference 1 >> Thiessen Polygon 10 >> Touches 4, 11, 12 >> Union with one Layer 5 >> Union with two Layers 1 >> Within 4, 12 >> >> >> >> Regards, >> >> Uwe >> >> >> ------------------------------------------------------------------------- >> This SF.net email is sponsored by: Splunk Inc. >> Still grepping through log files to find problems? 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