On Wed, Nov 15, 2017 at 10:03 PM, Markus Metz <[email protected]> wrote > On Wed, Nov 15, 2017 at 4:35 PM, Markus Neteler <[email protected]> wrote: >> >> On Wed, Nov 15, 2017 at 3:49 PM, Markus Metz >> <[email protected]> wrote: >> > On Wed, Nov 15, 2017 at 1:36 PM, Helmut Kudrnovsky <[email protected]> >> > wrote: >> >> >> >> Background of the question in subject: the GRASS algs in upcoming QGIS3 >> >> are working with v.external linked data. >> >> >> >> I've seen some modules doesn't work with such kind of data. >> >> >> >> Is there maybe a list already available? >> > >> > It depends also on the format that is linked in with v.external. For all >> > formats that do not have a key column (e.g. shapefile), attributes are >> > not >> > accessible, and attributes would get lost when modifying the >> > geometries.Therefore it is generally not safe to link vector data with >> > v.external. In many cases it does not make sense to use v.external >> > linked >> > data with simple features, instead vector data should be imported to get >> > true topology. If upcoming QGIS3 is working with v.external linked data, >> > the >> > GRASS interface of QGIS is effectively broken. >> >> I have turned this into a potential new snippet for the v.external manual: >> >> ----- snip ----- >> Due to these data model differences <em>v.external</em> does not work >> with all data formats. In general, for all formats that do not have a >> key column (e.g. SHAPE file), attributes are not accessible, and >> attributes >> would get lost when modifying the geometries. Therefore it is generally >> not safe to link vector data with <em>v.external</em>. In many cases it >> does not make sense to use <em>v.external</em> linked data with simple >> features, instead vector data should be imported with <em>v.import</em> >> or <em>v.in.ogr</em> to get true topology support. Importantly, point >> cloud data which do not have topology, can be linked with >> <em>v.external</em> > > as long as there are no attributes attached to these point cloud data, or if > the format of the point cloud data has a key column that allows to link > vector geometries to attributes.
Thanks, added in r71743 (and backported). >> ----- snap ----- >> >> Please review. > > Importing point cloud data is fast, therefore there is little gain in using > v.external instead of v.in.ogr. I wonder how much disk space that would save? markusN _______________________________________________ grass-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-dev
