[Marble-devel] Order of latitude and longitude in the UI

[Torsten Rahn]

Hi,

We had discussed this issue years ago (around 2006 IIRC). At that time the 
issue was a vi vs. emacs topic: There were schools which preferred LatLon 
(mostly in GPS circles) and others which preferred LonLat. Back at that time 
there didn't seem to be a clear preference (also Wikipedia articles at that 
time were sparse on geographical data compared to what is there today).

So we settled on Lon-Lat (which is also reflected in our Coding Guidelines):

https://projects.kde.org/projects/kde/kdeedu/marble/repository/revisions/master/entry/CODING

the only exception being namings which follow certain standards that get 
implemented (like KML).

Thinking about it I could even imagine that the preferred lon-lat/lat-lon 
order might be subject to i18n/l10n: Personally I rembember that early at 
school we were taught that the "correct" order would be "Länge, Breite". Then 
again looking into a Diercke World Atlas from 2009 (5th edition, the Diercke 
is a popular school atlas in Germany) I see a description: "Jeder Punkt auf 
der Erdoberfläche ist durch Angabe der Längen- und Breitengrade genau 
festgelegt. Beispiel: La Paz 16°30' Süd, 68°09' West."  (note the order of 
terms vs. actual example).

If you trust Google Fight there is a clear preference:

http://www.googlefight.com/index.php?lang=en_GB&word1=latlon&word2=lonlat

Of course things have surely changed recently with all things geospatial 
becoming more popular for the public (and of course with Google having a big 
influence on the way geo-information gets spread). 
So we definetely should reconsider the choice we've made so far (at least for 
the UI --- API-wise this would be more problematic). It's important that we do 
it in a good way in terms of education as well as standards:

I looked at your web links (some of which were familiar to me already): In 
general think we should follow the OGC standard(s) where ever possible, so 
this is something we need to take into account.  
 
On Monday, 31. October 2011 19:13:53 Friedrich W. H. Kossebau wrote:
> And only this way, no config option. Why?

Because so far nobody has raised a concern with the current way it gets 
displayed. And of course we want to avoid clutter in the user interface, so we 
haven't been keen on making everything configurable (but just those things 
where it makes sense).
  
> At least for the CRS typically used (which is BTW? And also used in
> Marble?).

Well we assume that our data is created following WGS84 (which usually is the 
case). In terms of math we usually expect right-hand coordination systems.
 
> Could that at least be made a configuration option, in which order to
> render the coordinates or copy to clipboard? I would provide a patch for
> this "bug"

The question is how to do this best (i.e. in a way that it doesn't introduce 
clutter).

We could add it to the Marble settings dialog under "View"->"Units".
Currently we have an option there which allows to toggle the angle notation: 

Angle: Degree (DMS) / Degree (Decimal)

Note that in the future we will have e.g. UTM added there which has no 
latitude vs. longitude (so if we add such an option it would probably get 
grayed out for the other cases).


One possible way to do this would be to enhance the dialog with an example 
representation like this:

Angle: 				Degree (DMS)
            				54° 48' N [ <-> ] 9°24' E

... where the "[<->]" would be a button (with a double arrow) that allows to 
toggle the default order. This would hide the (not very important) order 
configuration inside a practical example that can also help the user to 
illustrate what DMS vs. Decimal means.

Of course it would also be possible to do it like this:

Angle: 				Degree (DMS)
Coordinate Order: 	Latitude / Longitude 

But for somebody who is not used to the geographical terms that might be a bit 
too abstract. So I'm currently leaning more to the example-based way to 
configure this. What do you think? Any other suggestions?
 
BR,
Torsten

> :)
> 
> Cheers
> Friedrich
> 
> PS: Some interesting pages I found on this issue:
> http://gis.stackexchange.com/questions/6037/latlon-or-lonlat-whats-the-righ
> t- way-to-display-coordinates-and-inputs
> http://www.directionsmag.com/articles/a-history-of-the-order-of-x-y-and-z-1
> 50- and-why-its-important/122601
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