label vertices of polygon

[Barrett Higman]

Hi all,

 

Does anyone know if it is possible to label the vertices of a polygon (for example, with their coordinates) without having to turn them into a point layer first?

 

Cheers,

Barrett

 

 

 

Barrett Higman GIS and Assets Officer   (03) 5755 0555

Alpine Shire Council ABN 14 821 390 281 2 Churchill Avenue, Bright PO Box 139, Bright, VIC, 3741

This transmission is confidential. This email, including any attachments, is for the original addressees only. Any use, copying or disclosure by any other person is prohibited. If you have received this transmission in error, please delete this message and notify us by email immediately at in...@alpineshire.vic.gov.au 

 

[Bryce Touchstone]

Gheez, that would be tricky.

Isn't there a way to label polygon vertices with a 0 or 1 depending on whether they are mid-points or end-points, respectively? 

Crap, that would still probably involve translating them.

I highly doubt it, Barrett, given that I'm not sure how to label parts of an individual feature separately, which is essentially what you are trying to do here.

Good luck,

Bryce

Bryce Touchstone

 

The prudent see danger and take refuge, but the simple keep going and suffer for it.

Proverbs 27:12

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[Bill Williamson]

Don't have much a clue but I think we need more a real world example to understand the application Barrett. You've seen the Geometry Functions in the labelling dialog?

[Barrett Higman]

I ended up going for the data conversion option as I had to get it out the door, however, I did discover the nodes_to_points function which possibly could have helped, I just didn’t have time to investigate… and now I’m on to other things J.

 

Bill – I just had someone ask for the coordinates of title boundary corners so that they could get an idea of where the boundary is when they’re out in the field with a GPS. They are reasonably old school so they just wanted a hardcopy map with coords labelled.

 

Incidentally I did have time to quickly muck around with transforming the CRS of the coord labels on-the-fly from their native Cartesian coords to lat/lon. In case anyone is interested I used the following:

 

round(x(transform($geometry , 'EPSG:28355', 'EPSG:4326')), 6)  ||  '\n'  || round(y(transform($geometry , 'EPSG:28355', 'EPSG:4326')), 6)

 

Cheers,

Barrett

 

 

Barrett Higman GIS and Assets Officer   (03) 5755 0555

Alpine Shire Council ABN 14 821 390 281 2 Churchill Avenue, Bright PO Box 139, Bright, VIC, 3741

This transmission is confidential. This email, including any attachments, is for the original addressees only. Any use, copying or disclosure by any other person is prohibited. If you have received this transmission in error, please delete this message and notify us by email immediately at in...@alpineshire.vic.gov.au 

 

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[Bill Williamson]

Good to know, ta

[Nyall Dawson]

On Monday, 1 August 2016 10:51:38 UTC+10, Barrett Higman wrote:

Hi all,

 

Does anyone know if it is possible to label the vertices of a polygon (for example, with their coordinates) without having to turn them into a point layer first?

Not yet - 

What's needed here is an equivalent of 2.14's symbology "geometry generators" (or was that introduced in 2.16? I lose track...), but for labeling.

If this was implemented then the geometry of a feature could be modified just when it is being used for the labeling engine, ie using the nodes_to_points function to convert a line/polygon's vertices into points, which are then labeled just like points would be.

This would open up a TON of possibilities for cartography in QGIS, such as using a smooth/simplify function on a line feature to get nicer curved labels, using a secondary geometry column for curved labels inside water bodies/oceans, etc.

It's been discussed a lot within the QGIS development community, but we're needing someone to raise their hand and provide funding so that this can get implemented. This could be a good opportunity for the Australian QGIS community to band together and support the project through this sponsorship!

Cheers,

Nyall