Re: [Tagging] Waterway length

[Werner Hoch]

Hi,

it is an optional tag an it is useful for quality checks of the data.

Am Dienstag, den 29.01.2019, 18:37 +0300 schrieb Eugene Podshivalov:
> Hi all,
> The relation:waterway wiki page recommends using "distance" tag for
> "the total length of river in km". Was there any discussion of this
> choice?
> It seems a bit incorrect and confusing, because "distance" is more
> suitable for routes as discribed on its proper page. The existing
> "length" tag would fit better, woudn't it?

length vs. distance is only a wording issue.

The tag just enables you to compare the geometric length with the
lenght tag. If they are close (maybe within 5% of error) the river is
mapped fine.

As many length tags might have been taken from wikipedia (or wikidata)
it is redundant as soon as you add a wikidata tag.
see https://www.wikidata.org/wiki/Q584 (Rhine on Wikidata with its
lenght 1232.7 km).

Geometrical analyses of the river: 1160.34 km.

Not a precics match, but close enought that no major parts of the river
is missing.

Regards
Werner


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Re: [Tagging] Waterway length

[Eugene Podshivalov]

It is not possible to calculate length of an international river when
working with country extracts.

Eugene

пн, 18 февр. 2019 г. в 07:00, André Pirard :

> On 2019-02-16 23:00, Markus wrote:
>
> On Sat, 16 Feb 2019, 20:06 Eugene Podshivalov 
>> What is the best way to correct this, so that all other langauge pages
>> got the correction as well?
>>
>
> I'm not aware of any other way than correcting it on each page. I've just
> done this and also added a note that this tag lacks verifiability.
>
>>
> In June 2013, the notes help page was saying
>
> Leave a short message on the map if something is missing or obviously
> wrong, like "oneway in wrong direction"...
>
> I made a correction in English, French and Russian and asked the linguists
> to translate it to other languages.
> I suggested *thinking twice* to the persons who write notes as follows:
>
> Leave a short message on the map if something is missing or obviously
> wrong, like "oneway goes northbound" or "bridge or level_crossing?".
> These reports can be processed by map editors. Add the message
> understandably and thoughtfully, e.g. not "oneway in wrong direction"
> because someone could have flipped the direction before the note is read.
>
> I see that, English people are requested to stop *thinking twice*
> because, as it often happens to what one does for OSM, that advice has been
> removed from the English version, that French and Russian people must
> continue to think twice because the text remained and that German people
> and probably others were always requested to continue making errors because
> the text never changed:
>
> Gib einen kurzen Hinweis auf der Karte, wenn etwas fehlt oder falsch ist,
> z.B. ein "*Einbahn in der falschen Richtung*" ...
>
> Removal happened to other corrections I made, that's the way OSM goes.
> I hope I have answered your question, Eugene.
>
> All the best,
>
> André.
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Re: [Tagging] Waterway length

[André Pirard]

On 2019-02-16 23:00, Markus wrote:
On Sat, 16 Feb 2019, 20:06 Eugene Podshivalov  wrote:


What is the best way to correct this, so that all other langauge
pages got the correction as well?


I'm not aware of any other way than correcting it on each page. I've 
just done this and also added a note that this tag lacks verifiability.




In June 2013, the notes help page was saying
Leave a short message on the map if something is missing or obviously 
wrong, like "oneway in wrong direction"...
I made a correction in English, French and Russian and asked the 
linguists to translate it to other languages.

I suggested _thinking twice_ to the persons who write notes as follows:
Leave a short message on the map if something is missing or obviously 
wrong, like "oneway goes northbound" or "bridge or level_crossing?". 
These reports can be processed by map editors. Add the message 
understandably and thoughtfully, e.g. not "oneway in wrong direction" 
because someone could have flipped the direction before the note is read.
I see that, English people are requested to stop _thinking twice_ 
because, as it often happens to what one does for OSM, that advice has 
been removed from the English version, that French and Russian people 
must continue to think twice because the text remained and that German 
people and probably others were always requested to continue making 
errors because the text never changed:
Gib einen kurzen Hinweis auf der Karte, wenn etwas fehlt oder falsch 
ist, z.B. ein "*Einbahn in der falschen Richtung*" ...

Removal happened to other corrections I made, that's the way OSM goes.
I hope I have answered your question, Eugene.

All the best,

André.


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Re: [Tagging] Waterway length

[André Pirard]

On 2019-02-17 12:55, Eugene Podshivalov wrote:
вс, 17 февр. 2019 г. в 00:11, André Pirard >:


It's easy to make a script to total up all the segments of a
waterway or any way.


It will work but only if the entire river from its spring to mouth is 
drawn precisely enough, all relation roles are labeled properly and 
nobody breaks the labeling by intent or mistake some day.
The more side streams a river has the greater probabily is to break it 
one day.
Here is an example of such complex river which name means "a river of 
a hundred waterways"

https://www.openstreetmap.org/relation/5561722#map=13/51.4077/25.2271

Cheers,
Eugene

The method I describe has the advantage that the length written in an 
OSM relation would be the only, or almost, number that shows exactly 
what it measures instead of other measures said better than others for 
no explained precise reason. The relation makes a consensus of what the 
river is, the number is right, and anyone having another conception of 
the river can explain it and compute the length difference the same way 
as the relation does.
Imprecision is to be corrected, just as I'm spending much time using 
JOSM to improve to a 20 cm precision errors of 3 to 5 m or more made 
with other editors.
I saved as a GPX file the relations that I found for rivers Le Rhône 
, La Meuse 
 and Байкал road 
 (going to Иркытск where 
a guy tried to sell me confiscated material such as cranes, lorries and 
railway wagons).
Anyone can use JOSM to make routes and save them as *.osm and *.gpx 
files without modifying OSM.


I tried to upload them to RouteYou , but it 
would limit the length.
I uploaded them to GPSies 
 but the lengths are 
bogus, apparently multiplied by a strange factor.


GPSies
real
×
GPSies name (by PapoudeOSM)
12,275.62 	614 	18 	OpenStreetMap La Meuse 
 (FR+BE)

15,052.41   812 20
	OpenStreetMap Rhône 


33,926.12   1 113   30
	OpenStreetMap Байкал road 




(Turn off waypoint display)

Anyway, that's the idea.

All the best,

André.


вс, 17 февр. 2019 г. в 01:18, Sergio Manzi >:


Sorry for the typo: of course Wikip_*a*_dia was meant to be
Wikip_*e*_dia!

On 2019-02-16 23:15, Sergio Manzi wrote:

Then why don't you submit a paper to the CNFG (http://www.cnfg.fr/) and 
correct the Wikipadia articles?

Sergio


On 2019-02-16 23:07, marc marc wrote:

Le 16.02.19 à 22:32, Sergio Manzi a écrit :

A static value for a river length in OSM, without any information about
its source

every tag you add into osm have a changeset with a source tag, isn't it?
so adding the lenght should/must also have a source (extrapolation (sum
of all way of a relation) of osm data is a source)

a few month ago, I have checked the length of Rhône [1]
the french wikipedia list 2 sources for the lenght... both are very fair
away of the lenght found after some work on osm data.
which one to choose? osm without hesitation. maybe it is not fair but at
least it is verifiable (everyone can load the relationship, see the
result and correct errors if necessary) while the other 2 sources
(including the official French source) are totally unverifiable.

unfortunately I did not send in osm the result of the cleaning because
it concerned partly errors in osm (mainly roles in the relationship)
but I started by purging everything that didn't interest me in the
relationship before fixing. it will have to be done again

[1]https://en.wikipedia.org/wiki/Rh%C3%B4ne
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Re: [Tagging] Waterway length

[Eugene Podshivalov]

>
> it is wrongly named (distance instead of length)

Has already been corrected (at least in the english wiki)

> it can assume multiple different values according to different sources

"length:source" can resolve this if needed.

> it is unverifiable "on the ground"

it is IMNSHO useless (*just point to a Wikipedia article to get this
> information*)

Let me ask you a question please: how do you verify "name:es" of a river
which flows in France?
Should we delete all "name:" tags and direct users to wikipedia
instead?

For that I guess  a better solution would be to use the fixme=* tag:
> "fixme: check that this river length is between 5499 and 7088 Km", for the
> Nile.

This would mean keeping fixme=* tag in every waterway relation forever
which contradicts its purpose.

Cheers,
Eugene

вс, 17 февр. 2019 г. в 16:36, Sergio Manzi :

> I think I know understand what usage you want to do of that "waterway
> length" datum (*or at  least that's what I'm reading in your last message*):
> use it as a "control" for checking if the waterway's segments add up to the
> "official" (*whatever that can mean...*) waterway length.  Or at least in
> part: that datum will be close to useless to check waterways with the
> complexity of the "*river of a hundred waterways*" and many similar ones.
>
> For that I guess  a better solution would be to use the fixme=* tag:
> "fixme: check that this river length is between 5499 and 7088 Km", for the
> Nile.
>
> TBH I see A LOT of issues with this tag:
>
>- it is wrongly named (*distance instead of length*)
>- it is unverifiable "on the ground"
>- it can assume multiple different values according to different
>sources
>- it is IMNSHO useless (*just point to a Wikipedia article to get this
>information*)
>
> Personally I'm leaning to propse to deprecate the usage of this key and
> subject that to a vote. What is the process for that?
>
> Sergio
>
>
> On 2019-02-17 14:07, Eugene Podshivalov wrote:
>
> вс, 17 февр. 2019 г. в 15:18, Sergio Manzi :
>>
>>   That's as old as data processing: "*garbage in, garbage out*". Let's
>> fix the data.
>
> Fixing data is a good thing but from utilization in production point of
> view the choice between unstable and stable data is not questioned.
> Competeness of data is even more important than its stability, and that
> unfortunately cannot be achieved that quickly. One can create a waterway
> relation with a length defined and then there may be a long run until all
> waterway segments are drawn properly to finally be able to compare it to an
> official length.
>
> You'll probably can find many different estimations about its length.
>> Which one are you going to choose?
>
>  I would take one from any encyclopedia (subject to its license) and that
> figure will at least serve other mappers as a guidence when searching for
> incomplete or broken rivers.
>
> Cheers,
> Eugene
>
>
> вс, 17 февр. 2019 г. в 15:18, Sergio Manzi :
>
>> On 2019-02-17 12:55, Eugene Podshivalov wrote:
>>
>>
>> It will work but only if the entire river from its spring to mouth is
>> drawn precisely enough, all relation roles are labeled properly and nobody
>> breaks the labeling by intent or mistake some day.
>>
>> That's as old as data processing: "*garbage in, garbage out*". Let's fix
>> the data.
>>
>> And yes, the river you pointed at is particularly complex and probably
>> geographers are pulling each other's hairs about computing its length.
>> You'll probably can find many different estimations about its length. Which
>> one are you going to choose?
>>
>> Sergio
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Re: [Tagging] Waterway length

[Sergio Manzi]

I think I know understand what usage you want to do of that "waterway length" 
datum (/or at  least that's what I'm reading in your last message/): use it as 
a "control" for checking if the waterway's segments add up to the "official" 
(/whatever that can mean.../) waterway length.  Or at least in part: that datum 
will be close to useless to check waterways with the complexity of the "/river 
of a hundred waterways/" and many similar ones.

For that I guess  a better solution would be to use the fixme=* tag: "fixme: 
check that this river length is between 5499 and 7088 Km", for the Nile.

TBH I see A LOT of issues with this tag:

  * it is wrongly named (/distance instead of length/)
  * it is unverifiable "on the ground"
  * it can assume multiple different values according to different sources
  * it is IMNSHO useless (/just point to a Wikipedia article to get this 
information/)

Personally I'm leaning to propse to deprecate the usage of this key and subject 
that to a vote. What is the process for that?

Sergio


On 2019-02-17 14:07, Eugene Podshivalov wrote:
> вс, 17 февр. 2019 г. в 15:18, Sergio Manzi  >: 
>
>   That's as old as data processing: "/garbage in, garbage out/". Let's 
> fix the data. 
>
> Fixing data is a good thing but from utilization in production point of view 
> the choice between unstable and stable data is not questioned.
> Competeness of data is even more important than its stability, and that 
> unfortunately cannot be achieved that quickly. One can create a waterway 
> relation with a length defined and then there may be a long run until all 
> waterway segments are drawn properly to finally be able to compare it to an 
> official length.
>
> You'll probably can find many different estimations about its length. 
> Which one are you going to choose? 
>
>  I would take one from any encyclopedia (subject to its license) and that 
> figure will at least serve other mappers as a guidence when searching for 
> incomplete or broken rivers.
>
> Cheers,
> Eugene
>
>  
> вс, 17 февр. 2019 г. в 15:18, Sergio Manzi mailto:s...@smz.it>>:
>
> On 2019-02-17 12:55, Eugene Podshivalov wrote:
>>
>> It will work but only if the entire river from its spring to mouth is 
>> drawn precisely enough, all relation roles are labeled properly and nobody 
>> breaks the labeling by intent or mistake some day.
>
> That's as old as data processing: "/garbage in, garbage out/". Let's fix 
> the data.
>
> And yes, the river you pointed at is particularly complex and probably 
> geographers are pulling each other's hairs about computing its length. You'll 
> probably can find many different estimations about its length. Which one are 
> you going to choose?
>
> Sergio
>
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Re: [Tagging] Waterway length

[Eugene Podshivalov]

вс, 17 февр. 2019 г. в 15:18, Sergio Manzi :
>
>   That's as old as data processing: "*garbage in, garbage out*". Let's
> fix the data.

Fixing data is a good thing but from utilization in production point of
view the choice between unstable and stable data is not questioned.
Competeness of data is even more important than its stability, and that
unfortunately cannot be achieved that quickly. One can create a waterway
relation with a length defined and then there may be a long run until all
waterway segments are drawn properly to finally be able to compare it to an
official length.

You'll probably can find many different estimations about its length. Which
> one are you going to choose?

 I would take one from any encyclopedia (subject to its license) and that
figure will at least serve other mappers as a guidence when searching for
incomplete or broken rivers.

Cheers,
Eugene


вс, 17 февр. 2019 г. в 15:18, Sergio Manzi :

> On 2019-02-17 12:55, Eugene Podshivalov wrote:
>
>
> It will work but only if the entire river from its spring to mouth is
> drawn precisely enough, all relation roles are labeled properly and nobody
> breaks the labeling by intent or mistake some day.
>
> That's as old as data processing: "*garbage in, garbage out*". Let's fix
> the data.
>
> And yes, the river you pointed at is particularly complex and probably
> geographers are pulling each other's hairs about computing its length.
> You'll probably can find many different estimations about its length. Which
> one are you going to choose?
>
> Sergio
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Re: [Tagging] Waterway length

[Sergio Manzi]

On 2019-02-17 12:55, Eugene Podshivalov wrote:
>
> It will work but only if the entire river from its spring to mouth is drawn 
> precisely enough, all relation roles are labeled properly and nobody breaks 
> the labeling by intent or mistake some day.

That's as old as data processing: "/garbage in, garbage out/". Let's fix the 
data.

And yes, the river you pointed at is particularly complex and probably 
geographers are pulling each other's hairs about computing its length. You'll 
probably can find many different estimations about its length. Which one are 
you going to choose?

Sergio



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Re: [Tagging] Waterway length

[Eugene Podshivalov]

вс, 17 февр. 2019 г. в 00:11, André Pirard :

> It's easy to make a script to total up all the segments of a waterway or
> any way.
>

It will work but only if the entire river from its spring to mouth is drawn
precisely enough, all relation roles are labeled properly and nobody breaks
the labeling by intent or mistake some day.
The more side streams a river has the greater probabily is to break it one
day.
Here is an example of such complex river which name means "a river of a
hundred waterways"
https://www.openstreetmap.org/relation/5561722#map=13/51.4077/25.2271

Cheers,
Eugene

вс, 17 февр. 2019 г. в 01:18, Sergio Manzi :

> Sorry for the typo: of course Wikip*a*dia was meant to be Wikip*e*dia!
> On 2019-02-16 23:15, Sergio Manzi wrote:
>
> Then why don't you submit a paper to the CNFG (http://www.cnfg.fr/) and 
> correct the Wikipadia articles?
>
> Sergio
>
>
> On 2019-02-16 23:07, marc marc wrote:
>
> Le 16.02.19 à 22:32, Sergio Manzi a écrit :
>
> A static value for a river length in OSM, without any information about
> its source
>
> every tag you add into osm have a changeset with a source tag, isn't it?
> so adding the lenght should/must also have a source (extrapolation (sum
> of all way of a relation) of osm data is a source)
>
> a few month ago, I have checked the length of Rhône [1]
> the french wikipedia list 2 sources for the lenght... both are very fair
> away of the lenght found after some work on osm data.
> which one to choose? osm without hesitation. maybe it is not fair but at
> least it is verifiable (everyone can load the relationship, see the
> result and correct errors if necessary) while the other 2 sources
> (including the official French source) are totally unverifiable.
>
> unfortunately I did not send in osm the result of the cleaning because
> it concerned partly errors in osm (mainly roles in the relationship)
> but I started by purging everything that didn't interest me in the
> relationship before fixing. it will have to be done again
>
> [1] https://en.wikipedia.org/wiki/Rh%C3%B4ne
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Re: [Tagging] Waterway length

[Sergio Manzi]

Sorry for the typo: of course Wikip_*a*_dia was meant to be Wikip_*e*_dia!

On 2019-02-16 23:15, Sergio Manzi wrote:
> Then why don't you submit a paper to the CNFG (http://www.cnfg.fr/) and 
> correct the Wikipadia articles?
>
> Sergio
>
>
> On 2019-02-16 23:07, marc marc wrote:
>> Le 16.02.19 à 22:32, Sergio Manzi a écrit :
>>> A static value for a river length in OSM, without any information about 
>>> its source
>> every tag you add into osm have a changeset with a source tag, isn't it?
>> so adding the lenght should/must also have a source (extrapolation (sum 
>> of all way of a relation) of osm data is a source)
>>
>> a few month ago, I have checked the length of Rhône [1]
>> the french wikipedia list 2 sources for the lenght... both are very fair 
>> away of the lenght found after some work on osm data.
>> which one to choose? osm without hesitation. maybe it is not fair but at 
>> least it is verifiable (everyone can load the relationship, see the 
>> result and correct errors if necessary) while the other 2 sources 
>> (including the official French source) are totally unverifiable.
>>
>> unfortunately I did not send in osm the result of the cleaning because 
>> it concerned partly errors in osm (mainly roles in the relationship)
>> but I started by purging everything that didn't interest me in the 
>> relationship before fixing. it will have to be done again
>>
>> [1] https://en.wikipedia.org/wiki/Rh%C3%B4ne
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Re: [Tagging] Waterway length

[Sergio Manzi]

Then why don't you submit a paper to the CNFG (http://www.cnfg.fr/) and correct 
the Wikipadia articles?

Sergio


On 2019-02-16 23:07, marc marc wrote:
> Le 16.02.19 à 22:32, Sergio Manzi a écrit :
>> A static value for a river length in OSM, without any information about 
>> its source
> every tag you add into osm have a changeset with a source tag, isn't it?
> so adding the lenght should/must also have a source (extrapolation (sum 
> of all way of a relation) of osm data is a source)
>
> a few month ago, I have checked the length of Rhône [1]
> the french wikipedia list 2 sources for the lenght... both are very fair 
> away of the lenght found after some work on osm data.
> which one to choose? osm without hesitation. maybe it is not fair but at 
> least it is verifiable (everyone can load the relationship, see the 
> result and correct errors if necessary) while the other 2 sources 
> (including the official French source) are totally unverifiable.
>
> unfortunately I did not send in osm the result of the cleaning because 
> it concerned partly errors in osm (mainly roles in the relationship)
> but I started by purging everything that didn't interest me in the 
> relationship before fixing. it will have to be done again
>
> [1] https://en.wikipedia.org/wiki/Rh%C3%B4ne
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Re: [Tagging] Waterway length

[Eugene Podshivalov]

Thank you, Markus.

Cheers,
Eugene

вс, 17 февр. 2019 г. в 01:01, Markus :

> On Sat, 16 Feb 2019, 20:06 Eugene Podshivalov 
>> What is the best way to correct this, so that all other langauge pages
>> got the correction as well?
>>
>
> I'm not aware of any other way than correcting it on each page. I've just
> done this and also added a note that this tag lacks verifiability.
>
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Re: [Tagging] Waterway length

[Markus]

On Sat, 16 Feb 2019, 20:06 Eugene Podshivalov  What is the best way to correct this, so that all other langauge pages got
> the correction as well?
>

I'm not aware of any other way than correcting it on each page. I've just
done this and also added a note that this tag lacks verifiability.

>
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Re: [Tagging] Waterway length

[Sergio Manzi]

TBH, I'm all with you (/and maybe I'm seen as an eccentric too.../) and I see 
the tagging of waterways length as egregiously useless.

Beside, I smell a lack of verifiability [1] in this waterways property: I'm not 
a geographer, by far, but in the years I made up my mind that this is one of 
those things that experts debate in their congresses and can be object of 
accademic thesis.

On the other hand a tool to compute the total length of waterways from their 
source (/once you have pinpointed it/) to their mouth (/again, once you have 
pinpointed it/), could be really interesting.

A static value for a river length in OSM, without any information about its 
source (/pun not intended, but valid anyway.../), is the kind of information I 
will usually route to /dev/null and for which I'll seek more autortiative 
sources (/again.../)

Sergio


[1] https://wiki.openstreetmap.org/wiki/Verifiability

On 2019-02-16 22:10, André Pirard wrote:
> It's easy to make a script to total up all the segments of a waterway or any 
> way.
> ...
> But I seem like not well understood or maybe seen as eccentric.


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Re: [Tagging] Waterway length

[André Pirard]

On Sat, 16 Feb 2019, 15:26 Andy Mabbett  wrote:


   I would suggest that values entered by human mappers are more likely
   to be "error prone"; and that we should be more concerned with
   on-the-ground reality than "offical" figures.


It's easy to make a script to total up all the segments of a waterway or 
any way.
It would be already done if the routers added "by boat" to my suggested 
"by plane" ("as the crow flies").
I suggested that real routes can be made of multiple segments of those 
various kinds.

Like a car travel followed by a hike including a canoe trip.
Like the Tour de France (some parts by plane).
But I seem like not well understood or maybe seen as eccentric.

All the best,

André.


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Re: [Tagging] Waterway length

[Eugene Podshivalov]

What is the best way to correct this, so that all other langauge pages got
the correction as well?

Cheers,
Eugene

сб, 16 февр. 2019 г. в 21:57, Markus :

> On Sat, 16 Feb 2019, 00:43 Eugene Podshivalov 
>> The use of "distance" for river length distracts me as well.
>> But I'm trying to find its origin on this wiki page
>> https://wiki.openstreetmap.org/wiki/Relation:waterway
>> distance  * (optional) 
>> Total
>> length of river in km
>>
>
> This has been added more than four years ago, see:
>
>
> https://wiki.openstreetmap.org/w/index.php?title=Relation:waterway=1120648
>
> Regards
>
> Markus
>
>
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Re: [Tagging] Waterway length

[Markus]

On Sat, 16 Feb 2019, 15:26 Andy Mabbett  I would suggest that values entered by human mappers are more likely
> to be "error prone"; and that we should be more concerned with
> on-the-ground reality than "offical" figures.
>

I agree. Besides, official figures may not be compatible with OSM's licence.

>
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Re: [Tagging] Waterway length

[Markus]

On Sat, 16 Feb 2019, 00:43 Eugene Podshivalov  The use of "distance" for river length distracts me as well.
> But I'm trying to find its origin on this wiki page
> https://wiki.openstreetmap.org/wiki/Relation:waterway
> distance  * (optional) Total
> length of river in km
>

This has been added more than four years ago, see:

https://wiki.openstreetmap.org/w/index.php?title=Relation:waterway=1120648

Regards

Markus
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Re: [Tagging] Waterway length

[Andy Mabbett]

On Sat, 16 Feb 2019 at 13:46, Eugene Podshivalov  wrote:
>
> сб, 16 февр. 2019 г. в 16:30, Andy Mabbett :

>> Why would we tag either, when software can calculate them?

> Calculated value may differ from the official one and is error-prone

I would suggest that values entered by human mappers are more likely
to be "error prone"; and that we should be more concerned with
on-the-ground reality than "offical" figures.

-- 
Andy Mabbett
@Pigsonthewing http://pigsonthewing.org.uk

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Re: [Tagging] Waterway length

[Daniel Koć]

W dniu 16.02.2019 o 15:00, Sergio Manzi pisze:
> On 2019-02-16 14:46, Eugene Podshivalov wrote:
>> Calculated value may differ from the official one ...
>
> Official according to whom?
>
Good question - who can we trust?

The question is also how to calculate them? If a river has a fork (or
even multiple forks in its delta), what should we do - add all their
length (the simplest code would do it using database entries), choose
one (which and how?), make an average or maybe something else?...

Which also means we have to know exactly which parts carry the same
name, which is also not always easy to determine, since most of the
waters on Earth are connected and people just name some of them, but not
in a precise way and the name is not visible on the surface.

So adding official length tag makes sense for me, just like the official
population or borders, however source is needed then.


-- 
"I see dead people" [Sixth Sense]



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Re: [Tagging] Waterway length

[Sergio Manzi]

On 2019-02-16 14:46, Eugene Podshivalov wrote:
> Calculated value may differ from the official one ...

Official according to whom?

From https://en.wikipedia.org/wiki/Nile#cite_note-length-1 :

/"The length of the Nile is usually said to be about 6,650 km (4,130 mi), 
but reported values lie anywhere between 5,499 km (3,417 mi) and 7,088 km 
(4,404 mi). The length measurements of many rivers are only approximations and 
differ from each other because there are many factors that determine the 
calculated river length, such as the position of the geographical source and 
the mouth, the scale of measurement, and the length measuring techniques"/

From https://en.wikipedia.org/wiki/Amazon_River :

"/The Amazon River ... in South America is the largest river by discharge 
volume of water in the world, and //*by some definitions*//it is the longest./" 
(/my emphasis/)

Encyclopedias are the preferred source for this kind of information, not maps 
(or GIS databases).

Sergio



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Re: [Tagging] Waterway length

[Eugene Podshivalov]

сб, 16 февр. 2019 г. в 16:30, Andy Mabbett :
Why would we tag either, when software can calculate them?
Calculated value may differ from the official one and is error-prone, e.g.
when a segment is deleted by mistake or when a segment role is changed
between main and side stream.

Cheers,
Eugene

сб, 16 февр. 2019 г. в 16:30, Andy Mabbett :

> On Fri, 15 Feb 2019 at 23:31, Graeme Fitzpatrick 
> wrote:
>
> > The Nile rises in Lake Victoria & travels to the Mediterranean with
> > a length of ~6695km (depending on reference used), but the distance
> > between Kampala, on the north shore of Lave Victoria & Cairo is only
> > 3300km.
>
> Why would we tag either, when software can calculate them?
>
> --
> Andy Mabbett
> @pigsonthewing
> http://pigsonthewing.org.uk
>
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Re: [Tagging] Waterway length

[Andy Mabbett]

On Fri, 15 Feb 2019 at 23:31, Graeme Fitzpatrick  wrote:

> The Nile rises in Lake Victoria & travels to the Mediterranean with
> a length of ~6695km (depending on reference used), but the distance
> between Kampala, on the north shore of Lave Victoria & Cairo is only
> 3300km.

Why would we tag either, when software can calculate them?

-- 
Andy Mabbett
@pigsonthewing
http://pigsonthewing.org.uk

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Re: [Tagging] Waterway length

[André Pirard]

  
  
On 2019-02-16 00:41, Eugene Podshivalov
  wrote:


  
The use of "distance" for river length distracts
  me as well.
  But I'm trying to find its origin on this wiki page
https://wiki.openstreetmap.org/wiki/Relation:waterway
  

  

  distance
  * (optional)
  Total length of river in km

  

  

  

не
знаю, почему это так
это
как, it's just like

  

  speed
  
  * (optional)
  height of the  building
  

  

it should be changed as well (re-written)
and other distances for lengths if there is


  

  Cheers,
  Eugene

  
  
  
сб, 16 февр. 2019 г. в 02:33,
  Graeme Fitzpatrick :


  



  On Sat, 16 Feb 2019 at
01:38, Eugene Podshivalov 
wrote:
  
  

  
André, that's correct but do you happen to know
  why "distance" was selected for route and waterway
  length then?
  

  
  
  
  No idea why, but rivers should certainly be shown
with a length.
  
  
  EG The Nile rises in Lake Victoria & travels to
the Mediterranean with a length of ~6695km (depending on
reference used), but the distance between Kampala, on
the north shore of Lave Victoria & Cairo is only
3300km.
  
  
  OSM shows it fairly accurately as 6853km but as a
distance, when it should clearly be a length - may be a
re-write required?
  
  
  Thanks


Graeme
  

  
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Re: [Tagging] Waterway length

[Eugene Podshivalov]

The use of "distance" for river length distracts me as well.
But I'm trying to find its origin on this wiki page
https://wiki.openstreetmap.org/wiki/Relation:waterway
distance  * (optional) Total
length of river in kmCheers,
Eugene

сб, 16 февр. 2019 г. в 02:33, Graeme Fitzpatrick :

>
> On Sat, 16 Feb 2019 at 01:38, Eugene Podshivalov 
> wrote:
>
>> André, that's correct but do you happen to know why "distance" was
>> selected for route and waterway length then?
>>
>
> No idea why, but rivers should certainly be shown with a length.
>
> EG The Nile rises in Lake Victoria & travels to the Mediterranean with a
> length of ~6695km (depending on reference used), but the distance between
> Kampala, on the north shore of Lave Victoria & Cairo is only 3300km.
>
> OSM shows it fairly accurately as 6853km but as a distance, when it should
> clearly be a length - may be a re-write required?
>
> Thanks
>
> Graeme
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Re: [Tagging] Waterway length

[Graeme Fitzpatrick]

On Sat, 16 Feb 2019 at 01:38, Eugene Podshivalov  wrote:

> André, that's correct but do you happen to know why "distance" was
> selected for route and waterway length then?
>

No idea why, but rivers should certainly be shown with a length.

EG The Nile rises in Lake Victoria & travels to the Mediterranean with a
length of ~6695km (depending on reference used), but the distance between
Kampala, on the north shore of Lave Victoria & Cairo is only 3300km.

OSM shows it fairly accurately as 6853km but as a distance, when it should
clearly be a length - may be a re-write required?

Thanks

Graeme
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Re: [Tagging] Waterway length

[Eugene Podshivalov]

André, that's correct but do you happen to know why "distance" was selected
for route and waterway length then?

Cheers,
Eugene

вт, 29 янв. 2019 г. в 22:41, André Pirard :

> On 2019-01-29 16:37, Eugene Podshivalov wrote:
>
> Hi all,
> The relation:waterway wiki page
>  recommends using
> "distance" tag for "the total length of river in km". Was there any
> discussion of this choice?
> It seems a bit incorrect and confusing, because "distance" is more
> suitable for routes as discribed on its proper page
> . The existing "length"
> tag would fit better, woudn't it?
>
> Cheers,
> Eugene
>
> A *distance* is the length of the straight line between two points or,
> for that matter, the two ends of any line.
> They can be *far* or *near*.
> The *length* of a line is the number of meters that your odometer
> measures if you follow every bend of it.
> Mathematically, it is the sum of the lengths of tiny slices of the line
> that can be taken as straight (and the shorter the straighter, that's
> "infinitesimal analysis" but don't tell anybody).
> That is what is called "traveling a *long* road".
> So, to go from one point to another, you may follow two routes one of
> which is *longer* than the other and, yet, you won't have moved any
> *farther* (no more *distantly* if I may say).
>
> So, it is a mistake to talk of the distance of a *route*, it is a *length*
> .
> And be it macadam, water, rail or cycling or footing etc., it doesn't
> change anything to that.
>
> All the best,
>
> André.
>
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[Tagging] Waterway length

[Eugene Podshivalov]

Hi all,
The relation:waterway wiki page
 recommends using
"distance" tag for "the total length of river in km". Was there any
discussion of this choice?
It seems a bit incorrect and confusing, because "distance" is more suitable
for routes as discribed on its proper page
. The existing "length"
tag would fit better, woudn't it?

Cheers,
Eugene
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