Check QGIS/ArcGIS algorithms

[martinfleis]

https://pro.arcgis.com/en/pro-app/latest/tool-reference/cartography/collapse-road-detail.htm https://pro.arcgis.com/en/pro-app/latest/tool-reference/cartography/merge-divided-roads.htm https://desktop.arcgis.com/en/arcmap/latest/tools/cartography-toolbox/how-simplify-line-works.htm

[anastassiavybornova]

@martinfleis the idea is that your studets will help us with this one now? :) the arcgis tool i had in mind is linked above, but i'm sure there are more... (also in qgis potentially) if i find any will link them here

[martinfleis]

Yeah. Especially with Arc.

[Kryndlea]

The function "Merge divided roads" in ArcGIS works does not work well for our purposes. There is a global parameter "merge distance" where you need to specify a minimum distance apart for the two lines that you want to merge. After some research of the city network I chose the distance to be 12 meters.

While it works well in some cases, it performs poorly in others. The issue is the global setting of the distance, which also requires some knowledge of the city network. 1) If the roads/streets in the city centres or residential areas are too close, they get merged as well. 2) And if the roads are too far apart (highways) they do not get merged. 3) In this case, the roads got merged, but the blue one in upper right corner got shifted, which also happened in the previous case.

[Kryndlea]

The "Collapse road detail" function will only make major changes to the network if the "merge divided roads" function has already been applied to the data. It also requires parameter for the collapse distance, which requieres some knowledge of the city network as well.

This image represents the data after the implementation of the "merge divided roads" function.

This image represents the output of the "collapse road detail" function with a set distance of 50 meters .

It works well with roundabout entrances and with smaller roundabouts, but it fails to deal with the bigger ones. If the distance is changed to 100 meters it fails to collapse some larger objects as well but it also collapses smaller blocks of streets, which i believe is not what we want.

So once again, it is dependant on the global distance parameter.

I know it's not as clear from these screenshots, but wehn you overlay the layers in ArcGIS, it's easier to compare.

[dancejod]

There doesn't seem to be a function for collapsing linear features in standalone QGIS. I checked out several plugins, but they mostly don't have what we want, most of them (e.g. Geometric Attributes, HCMGIS, Geo Simplification) are only able to construct chordal axes of polygons. There is this plugin Cartography tools that actually has functions Collapse dual carriageways and Remove turnabouts, but I haven't managed to get them to work (the author had stated that it's still WIP).

Not QGIS, but there exists this Skeletron tool that could be useful.

[martinfleis]

@dancejod do you have a link to the Cartography tools plugin?

[dancejod]

@martinfleis here it is