[Talk-GB] man_made=survey_point

[Nick]

I have been looking at what is recorded under this tag in my area. I see 
that there aren't that many and those that are on OSM refer to trig 
points (see also http://trigpointing.uk/). My thinking is that if these 
are accurate and precisely marked on OSM then perhaps they could be used 
for resolving issue such as aerial imagery offsets.

I therefore wondered if it was worth using other data under this tag - 
specifically benchmarks (https://www.ordnancesurvey.co.uk/benchmarks/) 
as there are huge numbers in the UK. If these were marked on OSM and 
their accuracy and precision verified (OS open data is to the nearest 
10m square and transforming that adds errors), they could be helpful in 
local surveys where they are less than accurate but also for ensuring 
that moving all nodes in an area is valid (not just to match aerial 
imagery). A possible linked organisation with data is 
https://www.bench-marks.org.uk/

Incidentally, the benchmarks can be helpful if you need to align 
historical maps which have benchmarks shown.

Any thoughts?