<div dir="ltr"><div>Hi Jorge Tornero, Bernhard, Matthias, Nyall, All</div><div><br></div><div>Thanks for taking up the scalebar issue. </div><div><br></div><div>I agree that in most cases, the scalebar is more of an academic / customary. It hardly gives a "true" measurement.</div>
<div><br></div><div>Users generally use that as means of comparison and not to measure the exact distance.</div><div><br></div><div>IMO, the scalebar makes sense when you have maps in large scales like 1:100 better. Otherwise, its just an estimation.</div>
<div><br></div><div>Hope QGIS can provide a solution.</div><div><br></div><div>Regards</div><div>Ted</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Jun 27, 2014 at 1:27 PM, Ted <span dir="ltr"><<a href="mailto:tiruchirapalli@gmail.com" target="_blank">tiruchirapalli@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Richard, Matthias, All<br><div><br></div><div>Yes, the crash problem is gone in master (nightly built) version. Thanks a lot for the fix. Tested it on Win 7 x64 and also Win XP x32.</div>
<div><br></div><div>
Just for note, that issue is reported in v2.0.1 and v2.2 releases.</div><div><br></div><div>Will wait for the v2.4 release in July.</div><div><br></div><div><br></div><div>Regards</div><span class="HOEnZb"><font color="#888888"><div>
Ted</div><div><br></div><div><br>
</div><div><br></div></font></span></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Jun 25, 2014 at 5:02 PM, Bernhard Ströbl <span dir="ltr"><<a href="mailto:bernhard.stroebl@jena.de" target="_blank">bernhard.stroebl@jena.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Nyall,<br>
<br>
thanks for clarification!<br>
However I would say that even if using a projected coordinate system (map units m) scalebars are not neccessarily accurate all over the map: if your map covers a small area this may hold true but not if you look at continents.<br>
<br>
Bernhard<br>
<br>
Am <a href="tel:25.06.2014%2000" value="+12506201400" target="_blank">25.06.2014 00</a>:13, schrieb Nyall Dawson:<div><div><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On 25 June 2014 01:20, Bernhard Ströbl <<a href="mailto:bernhard.stroebl@jena.de" target="_blank">bernhard.stroebl@jena.de</a>> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
It does also matter in degrees, depending on the projection. same in<br>
meters: 1 cm on the map represents always a certain distance in<br>
reality (though this distance varies troughout the map depending on<br>
the projection and the area covered). If you look at the Lambert map,<br>
you realize that the distance between two parallels (10 degrees!)<br>
increases towards the pole, although in reality it is always (10*110km<br>
=) 1100 km. In the WGS84 map the distance between the parallels is<br>
constant but so is the distance between the meridians, but this is<br>
false as the distance gets less towards the pole in reality. So a<br>
scalebar (in m) being accurate in the middle of the map becomes less<br>
accurate towards the edges. Hence my question on which base the<br>
scalebar is calculated.<br>
</blockquote>
<br>
<br>
The question absolutely makes sense but I don't know the answer :)<br>
</blockquote>
<br>
<br>
Could you check? or whom would we have to ask?<br>
</blockquote>
<br>
It's calculated this way:<br>
<br>
If you're working in a projected coordinate system (ie, map units are metres):<br>
<br>
- Take the current extent of the map, calculate the width (x max - x<br>
min), divide this by the width on paper of the map<br>
<br>
If you're working in a geographic coordinate system (ie, map units are degrees):<br>
<br>
- Convert the width of the map (map's extent x max - x min) from<br>
degrees to metres, using a variant of the Haversine formula, and<br>
treating the current latitude as the MIDDLE LATITUDE from the map's<br>
extent<br>
- Convert this distance to a scale by dividing by the width on paper of the map<br>
<br>
So, yes, scalebars using m/km/miles/etc are only an approximation when<br>
map units are degrees, and are very inaccurate when used with maps<br>
covering a large area or for areas far from the equator.<br>
<br>
Nyall<br>
<br>
<br>
</blockquote>
<br>
<br></div></div>
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