[Qgis-developer] Snapping tolerance

[Zoltan Szecsei]

On 2014/12/14 15:20, Rouzaud Denis wrote:
>
> From my point of view, the settings of snapping are far too advanced 
> for 95% of the usage. Let’s not make them even more complicated, just 
> for a very specific use case.

Hi Denis,
I have to disagree with you, as someone who does a fair amount of 
digitising.

To support Ramon, I too work with many map layers in many different 
projections, so we mustn't lose facilities that we (even by accident) have.

Some points:

  * Being able to set a global tolerance in linear units, and have QGIS
    convert that to the relevant layer CRS would be VERY useful.
    ie: I want a 10m snapping tolerance even if I am on a LatLong map layer.
  * QGIS only allows Snap Modes "To Vertex", "To Segment" or "To Vertex
    and Segment"
    What if both a Line-end and a Vertex on that same line is within
    tolerance?
    We really need to differentiate between Point (the Start & End
    Vertex of a Line or Polygon), Vertex and Segment AND be able to set
    the Snapping order between those three components of a graphical entity.
  * The snapping order between layers is currently set to the order of
    the maps in your Layer Tree. Depending on the features you are
    digitising, this is not optimal as one often needs to have a layer
    snapping order different from the viewing order.
  * It would be useful to set the layer snapping order in the Snapping
    Options table, and have the _option_ (and not enforced by the
    developer) to prioritise the current map being edited.
  * If I remember correctly, snapping returns a position from the first
    layer it finds anything in, and IIRC if there are multiple snaps on
    that layer, the closest is returned? What if there are still
    unsearched layers that might have something within tolerance?

The above is just a couple of walls I have hit when trying to digitise 
large volume jobs with multiple feature types and map layers.


My 2c

Regards,
Zoltan


-- 

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Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services

P.O. Box 7, Muizenberg 7950, South Africa.

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