[OSM-talk] Azimuth measurement

[colliar]

On 08.04.2014 11:45, François Lacombe wrote:
> Hi,
> 
> Here is a topic discussed with a few people during State Of The Map FR
> last week end in Paris.
> 
> Some features mapping would require to tag their azimuth as for knowing
> how they are really installed in the environment.
> 
> For instance, benches mapped with nodes may be tagged with azimuth=*
> because nodes don't tell which direction the bench follows.

Think the tag is direction=* [1] but there is no explanation how to
measure.

> But how contributors can measure it ?
> 
> Common devices like smart phones carry compass captors, used by compass
> applications.
> These captors only sense the magnetic north to determine the azimuth of
> the device. The magnetic north is continuously diverting from the
> geographic north.
> Using the magnetic north isn't a good idea since the azimuth will be
> continuously changing instead from the geographic azimuth.
> There will be the same question regarding standard compasses.
> 
> Magnetic diversion is mathematically known and such azimuth could be
> converted into geographic ones.
> 
> Is there a solution to that issue ?

Take a photo to have a reference point either to adjust your compass
results later or to completely measure later.


Cheers colliar

[1] https://wiki.openstreetmap.org/wiki/Key:direction

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