[Tagging] Estimated values for height

marc marc marc_marc_irc at hotmail.com
Tue Nov 13 22:54:34 UTC 2018

Le 13. 11. 18 à 23:30, Nick Bolten a écrit :
> My primary concern is in being able to distinguish estimated values that 
> are "guesstimates" of different types from something where someone took 
> the effort to use something more precise. Examples:
> (1) Jessica is walking along the street and is prompted to estimate a 
> nearby building's height in meters. They eyeball it and says it's about 
> 3 meters wide and we record it. What's the best way to make a note that 
> this was acquired through visual inspection so that it can be 'flagged' 
> in later efforts for measurement with a ruler or laser or offset 
> satellite imagery, etc?

on the object it-self height=3
group all objet with this source, and put on the changeset : 
source=survey source:height=estimated or eyeball

> (2) Bartholomew is armchair mapping an area they are personally familiar 
> with and wants to estimate the width using JOSM's built-in distance 
> calculation tool. The tool tells them that it is 3.465839124 meters 
> wide, and they write that down in the tag. Of course, their error range 
> probably only justifies writing down "3.7 meters" at best, but we can't 
> ask Bart to know that for sure. How do we know that Bart's width 
> estimate is only from aerial imagery + a tool, and temper expectations?

let's assume that Bart is naive enough to believe that he has such accuracy
On the object it-self height=3.465839124
group all objet with this source, and put on the changeset : 
source=imagery imagery_used=the_name_of_this_aerial_imagery
but Bart being an osm contributor, we can hope he doesn't be so stupid 
and so he can round his own measure.
one day editors may be more advanced and will automatically
add a changeset tag like imagery_used:resolution=10cm/pixel
one day also one can expect that editors + evolved automatically shows 
next to each tag the changeset and the source of the changes and who 
last modified it

> (3) Katie is high tech and uses fancy laser and computer vision to get 
> centimeter-precision readings. How does she know which places are in 
> need of more accurate measurements, and how do we know her measurements 
> should be given the appropriating weighting vs. guessed numbers? i.e., 
> how do we know which height/width/etc values need accuracy improvements?

it's currently impossible given the lack of quality tags on the 
changeset (we still see too often changeset without even a source tag). 
but if the contributors added them, we could easily analyze them, a bit 
like geocropping to determine the poi that probably need to be confirmed.
but if tags are missing for this analysis, please don't try to solve 
this by encouraging source tags on objects that are in no way the 
guarantor of the current source of the object. Neither do you invent
a new tag to describe exactly the same thing as what exists like 


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