[Qgis-user] Micro-Geometry Problems

[Gabriel De Luca]

When digitizing, coordinates are taken from the canvas and stored to the
layer. If the canvas (project) CRS is not the same as the layer CRS, a
transformation and/or conversion must be done between the taken and stored
coordinates. That transformation and/or conversion performed between the
previous vertex to be rendered, and the rendered coordinate digitized to be
stored, may lead a round trip error.

If you are digitizing from a canvas CRS to the same layer CRS, and snapping
to vertex, I think that you will not see any difference between both
vertices.

If you are snapping to intersections, you can see a difference also working
in the same CRS for the canvas and the layer, because an intersection
calculated coordinate may not be a rational number and at some decimal
place it must be truncated.

I don't know if any rendering option could truncate the coordinate of a
vertex when rendering it, so when snapping to that vertex (in the same CRS
for the canvas and the layer) could return a truncated coordinate for the
digitized vertex.

El mar., 14 de ene. de 2020 a la(s) 18:59, <smiller192 at cfl.rr.com> escribió:

> All-
>
>
>
> I have digitized a land use/land cover layer as individual polygons.  The
> snap options were used and, for most vertices, the snap was precise.  A
> vertex in polygon A has a precise match to a vertex in neighboring polygon
> B.
>
>
>
> But in 582 out of 2799 polygons, there are mis-matches in adjoining
> vertices that are only evident if you zoom into the layer at a
> magnification (i.e., a scale) of from 20000:1 to 40000 to 1.  I have spent
> a couple of weeks trying to remedy these by hand using the Vertex Tool and
> other means.  My question is this: is there an automated way in QIS to
> detect and remedy these situations?
>
>
>
> Thanks,
>
> Steve Miler
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