Buffer task validation area to include data from neighboring tasks

[planemad]

When one maps within a certain area, the bigger picture of how the roads connect to the neighboring area is lost.

Even while validating everything looks perfect within the task boundary but when you download the data from the neighboring areas the seams become clearly visible due to the unconnected roads and missing features from the edges.

During validation it is thus important that the area downloaded is slightly larger than the tracing area so that broken data can be spotted and fixed easily without manually having to download surrounding areas.

The amount of overlap can be in the 1-2%range of the neighboring task. This would greatly help improve the quality of validation and make the process more thorough.

[ethan-nelson]

I'm not necessarily against this, but I see a few issues:

1. If someone is validating a completed tile next to a task being worked on, and the validator makes edits outside of the task region, that could create conflicts for the user in the task next door (who could very well be fixing these issues). This could potentially be happening very often if we have a high traffic task with multiple editors and validators.
2. Shouldn't validation be about that specific task? I understand the bigger picture need to ensure infrastructure is connected properly, but should we expect every person (especially new people) to download outside their task region to connect roads? How far away from the task boundary do we expect people to be obligated to edit outside of their task region?
3. If it is a completion-for-credit-based project, how does the person validating (who determines whether the contributor's edits are acceptable) know where the buffer region is and which is part of the task area?

[planemad]

@ethan-nelson

Good points, overall we just need a small amount of overlap in the range of 10-30m so that situations like the gif is avoided.

1. We have conflicts in any case when we are working on shared objects across blocks. What we might have is a small amount of duplication or overlap of new objects if neighbouring blocks were worked on at the same time. In the other cases, due to the overlap some roads from the neighbouring block will be downloaded allowing us to easily extend or join it to objects in the active block. Currently the opposite happens, where connections are usually missing between neighbouring blocks.
2. Not more than 30m of buffer is needed. Just enough to ensure that the end node of a way in the neighboring block is downloaded
3. Again, if the buffer is in the range of 30m, this is not a significant issue.

[harry-wood]

This is an issue for the original mapper as well as the validator. Not sure if the buffer idea is a good solution though. Sounds like it would be a bit confusing.

[planemad]

Duplicate of https://github.com/hotosm/osm-tasking-manager2/issues/290