Hi Markus, 2012/1/25 Markus Metz <markus.metz.gisw...@googlemail.com>: > 2012/1/25 Sören Gebbert <soerengebb...@googlemail.com>: >> >> 2012/1/25 Markus Metz <markus.metz.gisw...@googlemail.com>: >>> >>> Note that a GRASS layer is defined by the existence of at least one >>> vector feature with at least one category value in that layer. That >>> layer may or may not be attached to an attribute table. For examples, >>> see v.in.ogr when importing several layers at once, the LiDAR >>> filtering tools, or the vector output of r.stream.extract. >> >> I will have a look. > > Also the v.net.* modules, which make use of layers to distinguish > between line and node costs with the help of layers. >> >>> >>>> Why is a full vector copy needed in case of category transfer from one >>>> to another layer? >>> >>> Because category transfer takes place in the vector feature, i.e. >>> modifies the coor file of the vector. v.category option=transfer does >>> not add an attribute table (AFAIK). >> >> Maybe this function: >> off_t Vect_rewrite_line(struct Map_info *Map, int line, int type, >> const struct line_pnts *points, const struct >> line_cats *cats) >> >> can be used to add new layer using existing categories (from layer 1?) >> to an existing vector map? > > Adding a new layer always means adding new categories, also if they > are identical to categories in a different layer. The difference > between Vect_rewrite_line and the combination of Vect_delete_line, > Vect_write_line is only that Vect_rewrite_line is supposed to check if > the new line fits into the space used by the old line.
If i understand this correctly the vector library provides the mechanism to implement vector modules to add new layer and copying existing categories into the new layer using the same vector map? > >> >> My problem is that i want to successively add new layers (tables) to >> existing vector maps using existing categories. > > The problem is that the categories are not existing for a new layer > because of the definition of a new layer. If there would be categories > existing for that layer, the layer would already exist. > I guess you must either use v.category option=transfer or have a bunch > of tables but only one vector with one layer and disconnect/reconnect > the tables as needed, only one table would then be connected to the > vector at any given time. I have used that successfully for time > series points some time ago, it's the fastest solution but needs some > care in handling the tables. Probably not an option for the temporal > database unless you want to introduce db.table.timestamp... This is currently not an option. But i guess i can modify v.category to support the transfer of categories to more than a single layer of a new map: v.category --o input=soils output=soils1 option=transfer layer=1,2,3,4,5,6,7,8,9,...,2000 This will copy the cats of vector map soils from layer 1 into the new layer 1 - 2000 of vector map soils2. Can you estimate how hard the implementation will be? Best regards Soeren btw: * v.timestamp with layer support is in svn * Vector layer timestamp support in the temporal GIS implementation is in my local svn copy and needs more testing -> i need to create vector maps with multiple categorized layer. > > Markus M > > >> Additionally i need to >> timestamp the layer in the temporal database. It would be meaningful >> to timestamp layers at file level using v.timestamp too. >> An approach which i have in mind is to extent v.timestamp with a layer >> option, so that timetsamp text files can be created for each layer in >> the vector map directory. >> >> An application in the temporal GIS and for environmental modelling >> would be the observation of raster time series at specific vector >> point locations. The vector location do not change over time, but the >> attribute tables. Hence, for each observed time step a new timestamped >> layer and table will be added to the observation vector map and filled >> with raster values. >> >>> >>>> >>>> i just started to investigate the >>>> new shiny world of multiple layer usage. >>> >>> I hope you enjoy it! >> >> I do. :) >> >> Best regards >> Soeren >> >>> >>> Markus M >>> >>>> >>>> Best regards >>>> Soeren >>>> >>>> 2012/1/25 Martin Landa <landa.mar...@gmail.com>: >>>>> Hi, >>>>> >>>>> db.copy from_table=soil to_table=soil_2 >>>>> >>>>> -> makes copy of `soil` table >>>>> >>>>> v.db.addtable map=soil table=soil_2 layer=2 >>>>> >>>>> -> it would overwrite `soil_2` table, but do nothing in this case, no >>>>> feature have category defined in layer 2. >>>>> >>>>> Proposal: >>>>> >>>>> v.random --o -z seed=1 output=soil n=20 zmin=0 zmax=100 column=clay >>>>> v.category input=soil out=soil2 option=transfer layer=1,2 --o >>>>> db.copy from_table=soil to_table=soil_2 >>>>> v.db.connect map=soil2 table=soil_2 layer=2 >>>>> >>>>> v.db.addcolumn map=soil2 layer=1 columns='sand_frac DOUBLE PRECISION' >>>>> v.db.addcolumn map=soil2 layer=2 columns='sand_frac DOUBLE PRECISION' >>>>> ... >>>>> >>>>> Martin >>>>> >>>>> -- >>>>> Martin Landa <landa.martin gmail.com> * http://geo.fsv.cvut.cz/~landa >>>> _______________________________________________ >>>> grass-dev mailing list >>>> grass-dev@lists.osgeo.org >>>> http://lists.osgeo.org/mailman/listinfo/grass-dev _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
