Maybe some of you have QGIS 2.16.
When using Vector | Research tools | Select by location
The interface is not very informative about what is the purpose of the
Well, somebody at
pointed out a link on github.... qgis development.
Improve robustness of geometry predicates with new precision parameter in by
Snap geometries to a virtual grid of step precision before applying geometry
This also affect bbox used for index intersection.
These features were funded by: MEDDE (French Ministry of Sustainable
Just a little theoretical explanation of this would be very helpful... ...how
the virtual grid and the bounding box work for the algorithm.
I tested it with very small numbers but I don't know if this is affected by the
extent of the layer...
I'm wondering if this would be a kind of 'clustering tolerance' or fuzzy
tolerance, like that on ArcGIS products.
This 'tolerance' issue is important but, can it be applied into QGIS, and at
the same time, complying to Simple Features Standard?
I made some tests with dummy geodata in a spatialite db and Java Topology Suite
In QGIS, select by location (intersection) does not select a point that lies on
the boundary of a polygon or at the interior of a line segment. (using the SFA
definitions of boundary and interior....
if I want that bordering coincident point to be selected, then a vertex must
lie in the same place of that point (i tested it using ST_Snap in DB Manager's
This is true for all programs using SF but not for JTS. JTS seems more
'robust' applying predicate rules. I don't know why in JTS a point in a
boundary or line interior is selected using intersection but not in other
products... it is not the same algorithm? JTS java and GEOS
I guess is not that simple (infinite points in a line segment) but the rule for
intersects predicate states that an intersection is true if geometries share at
least a point, being on their interiors or boundaries....
By the way... having a 'buffer' parameter on select by location would be very
is somebody willing to fund it? crowd-sourcing?
PR Office of Management and Budget
787.725.9420 x 2409
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