1

I'm currently performing an network analysis where I calculated catchment areas for health facilities in a city. These catchment areas are overlapping and I want to clip these catchment areas with an underlying population layer which is devided in multiple polygons to see the individual amount of people living in each catchment area. If i use the 'clip' tool in qGIS, it merges all these catchment areas but that is not what I want(see image). I want to keep the individual catchment areas with their unique ID, clipped with the underlying layer without merging results. I currently doing it manually(by deleting all the catchment areas except for one), but that takes me ages. Is there a faster way?

enter image description here enter image description here

Improve this question
1
  • Would a Vector Overlay - Intersection get you what you want?
    – John
    Apr 18, 2018 at 13:50

2 Answers 2

Reset to default
1

A simple, easy overlooked button did the trick! I used the 'iterate over this layer' button and it worked perfectly. The only problem now is that the output features don't got the original catchment ID's. So it is very hard to link the newly made catchment areas with the right area. Is there a way that I can keep these ID and add them as a variable in the output features?

Improve this answer
3
  • Thanks for your feedback. Please see my update. Intersect will be the tool you need.
    – Kazuhito
    Apr 19, 2018 at 9:27
  • 1
    Sorry, I was to quick with my response. It works! many thanks again. This was of great value
    – tVaes
    Apr 19, 2018 at 9:39
  • Please do not apologize, it was conceivable requirement. Glad it worked!
    – Kazuhito
    Apr 19, 2018 at 9:41
0

QGIS 2.18.18

In the Processing Toolbox, there is SAGA | Vector polygon tools | Polygon clipping tool.

After selecting your catchment and population layers, click on on a tiny green Iterate over this layer button and execute this tool.

enter image description here

It will return Output features as per input catchment polygon.

enter image description here

Polygons hidden by overlying layer are also intact.

enter image description here

This operation can be very slow if you have many catchment polygons.

QGIS 3.0.1

You can do the same using QGIS | Vector overlay | Clip.

There is a problem with Iterate in QGIS 2.18.18 Clip function, so I chose SAGA Polygon clipping tool as a workaround.

Update

I understand you need id field from original Catchment polygons. Then please use Intersection tool as @johns has commented earlier. If you are using QGIS 2.18 and SAGA tool, it is in Processing Toolbox | SAGA | Vector polygon tools | Intersect.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.