track simplification

[Madeline Steele]

Hi all, 

I just noticed this change set: https://nrenner.github.io/achavi/?changeset=48513105. I reached out to the mapper to ask about the motivation for track simplification, and why the change set was so large. We'll see if I hear anything back. Anyhow, I just wanted to give you all a heads up and ask if you have any thoughts on these edits.

Thanks,

Madeline

[Madeline Steele]

Hi all, 

I got the following reply from the user:

while tagging the access restrictions of tracks in the forest in that area I noted that during a 2013 update of roads for Washington county for all newly added tracks (only these) no data cleanup seemed to be applied - most tracks have a constant spacing of 10-30 feet between nodes, IMO really excessive. Also, most track ends have little 3-node "loops" at their ends, about 1-2m in diameter, many intersections have similar short and 60 deg angled segments associated with them. Looks very much like artefacts from vectorizing raster data to me.

So I selected manually all applicable tracks (only those, no intention to touch other data) and used the JOSM simplification to 1m deviation on them, which on average removed 3/4 of the nodes from those tracks and eliminated most of those artefacts. I did actually do that in 4 or 5 batches, removing about 60.000 nodes in that general area.

This seems reasonable to me if you all are comfortable with it. 

Thanks,

Madeline

[Alan Millar]

Yeah, it sounds like they were paying attention and put some good thought into it.  I agree, it sounds reasonable and I'd call it an improvement.  :-)  

- Alan

On 05/10/2017 05:10 PM, Madeline Steele wrote:

Hi all, 

I got the following reply from the user:

while tagging the access restrictions of tracks in the forest in that area I noted that during a 2013 update of roads for Washington county for all newly added tracks (only these) no data cleanup seemed to be applied - most tracks have a constant spacing of 10-30 feet between nodes, IMO really excessive. Also, most track ends have little 3-node "loops" at their ends, about 1-2m in diameter, many intersections have similar short and 60 deg angled segments associated with them. Looks very much like artefacts from vectorizing raster data to me.

So I selected manually all applicable tracks (only those, no intention to touch other data) and used the JOSM simplification to 1m deviation on them, which on average removed 3/4 of the nodes from those tracks and eliminated most of those artefacts. I did actually do that in 4 or 5 batches, removing about 60.000 nodes in that general area.

This seems reasonable to me if you all are comfortable with it. 

Thanks,

Madeline

On Tuesday, May 9, 2017 at 1:23:28 PM UTC-7, Madeline Steele wrote:

Hi all, 

I just noticed this change set: https://nrenner.github.io/achavi/?changeset=48513105. I reached out to the mapper to ask about the motivation for track simplification, and why the change set was so large. We'll see if I hear anything back. Anyhow, I just wanted to give you all a heads up and ask if you have any thoughts on these edits.

Thanks,

Madeline

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[Peter Dobratz]

Looking at a few of the tracks it looks reasonable to me too.  I've had prior positive interactions with user emem and he seems like he knows what he's doing.

Peter

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