[OSGeo Africa] Undershoots and overshoots (was Re: What's up, need to meet)

[Tim Sutton]

Hi Nkonzo

See below for inline replies:

> On 07 Sep 2016, at 9:23 AM, Mvelase Nkonzo <mvelasenkonzo at gmail.com> wrote:
> 
> Hi Tim,


Please note that this is a general mailing list so it would be great if you could address your queries to the list as a whole - there are lots of other people on this list who can give you great advice....

Also please start a new question in a new thread - in particular the one you chose to attach your question to was probably ill chosen...

> 
> My name is Nkonzo, I am a trainee Technician at Gibb(Pty)Ltd. I'm working on a Rural Road Assessment Management System (RRAMS) project. So I need your favor since I'm new in QGIS, if you could help me fix the Undershoots and Overshoots of my intersections.

Do you want to fix it interactively or systematically? In the former case you should look at the snapping options in QGIS - see:

https://docs.qgis.org/2.2/en/docs/user_manual/working_with_vector/editing_geometry_attributes.html

You can set your roads to snap to edges and vertex and use a specified tolerance in pixels or map units. Then visit each under / over shoot and and drag the road end vertex towards the nearest intersection using the node tool.

For systematic / automatic fixes, you probably want to look at using GRASS (which you can do via QGIS) and PostGIS to clean your geometries. See for example this thread:

http://marc.info/?l=grass-user&m=142142976408748&w=2

No doubt others on this list could share their experience on this too. I would caution you to be careful when doing a systematic fix and include a Quality Assurance (QA) step in your processing as you may get undesirable side effects. Needless to say, always work on a copy of your data when doing this kind of work, and archive the before and after state so that you can roll back to before you automatically changed your geometries if needed.

Hope that helps, hopefully others can chip in with more specific advice.

Regards

Tim

PS when posting screenshots to the list, rather upload them to an image sharing site and then share a link to the image as this mailing list will filter out large attachments like screenshots automatically.

—









Tim Sutton

Co-founder: Kartoza
Project chair: QGIS.org

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