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I generally have an doubt about QGIS. Is it possible to Trace the feature in QGIS? As in the case like ArcGIS for Desktop which has a tool called "Trace" in its Editor Toolbar? If yes, how we can do it?

  • Hi Arun. Can you explain what exactly the requirements for a trace tool are? It will help people who are not familiar with the cited reference tool to understand your question. Thank you very much. – Matthias Kuhn Oct 29 '13 at 6:56
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    Trace Tool is the tool which is used trace the boundary of features without any vertex missing. It also reduces the chances the overlap and Gap Polygons from occuring.I have found this tool in ARC-GIS,while I am working on Urban Planning project.I am keen to whether this tool is avaliable in Qgis? – Arun Oct 29 '13 at 7:12
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Try the 'traceDigitize' plugin (get it by going Pulgins->Manage and Install Plugins and then either search by name or scan through the 'Get more' section).

EDIT (instructions)
You must first set snapping for the layer you want to trace (Settings->Options->Snapping Options). Then make a layer editable and begin tracing by clicking the trace tool button and then holding down the Ctrl key. Right click to finish the trace.

I have found that it is easy to get self-intersections by accidentally reversing over your own trace (even when you specify no intersections in the snapping options). Being careful helps! However, if you don't want to re-trace a shape, you can simply accept the invalid geometry, and then use the Vector->Geometry Tools->Check geometry validity tool to identify and highlight such errors. If you have loads, then trace more carefully, otherwise, it is easy enough just to tweak the errors to ensure valid geometry.

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There's a more recent plugin available now called AutoTrace:

https://plugins.qgis.org/plugins/autoTrace/

Some decent instructions are here:

http://www.lutraconsulting.co.uk/products/autotrace/

It's been a while since I did digitizing in Arc, but I found the AutoTrace plugin to be at least as easy as my memories of the ESRI version.

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