[Qgis-developer] QGIS Crash - Serious problem in 2x
Bernhard Ströbl
bernhard.stroebl at jena.de
Tue Jun 24 02:06:48 PDT 2014
Hi Matthias,
probably this is academical...
Am 24.06.2014 10:42, schrieb Matthias Kuhn:
> Hi Bernhard,
>
> I wouldn't say no sense at all. It strongly depends on the context, but
> if you have for example a lesson for geography students and are
> introducing CRS/projections and their properties one could want to add a
> scale bar in degrees.
But would that scalebar show the degrees for lon or lat?
If the first (lon) for which latitude?
Either of the two: how do you want to tell people that this scalebar is
only true for North-South (lat) or East-West (lon) measurements and must
not be used in any other direction? IMHO a scale bar is to enable
readers to use their ruler to measure a distance on the map in _any_
direction.
> I agree that it's not very common and most people
> are probably unused, but if you explicitly state the fact that the map
> is in degrees you might even avoid confusion and prevent people from
> trying to compare distances.
But adding a scale bar encourages users to compare distances! The fact
that a map is suitable to measure and compare distances is not decided
by the map units but by the used projection and the covered area. If
your map is in degrees just enable the graticules and (if useful) add a
scalebar in m/km/miles (does that work with degrees? I have not tried.
If not this would be a feature request.)
BTW: for which point of a map is the scale bar currently created
(thinking of non-distance-true projections and large areas e.g. continents)?
regards
Bernhard
>
> Best,
> Matthias
>
> On 24.06.2014 10:24, Bernhard Ströbl wrote:
>> Hi,
>>
>> IMHO a scale bar in degrees doesn't make sense at all apart from being
>> unused to readers of the map. Because one degree in latitude is always
>> (uhmm if I recall correctly) 110 km, in longitude this is only true
>> for the equator, the closer you get to the poles the less km per
>> degree in longitude (until 0 at the pole itself). If you display only
>> a small part of the earth you migth manage with two scale bars
>> (lon/lat) but how would you imagine a scale bar for e.g. north America?
>>
>> Bernhard
>>
>> Am 24.06.2014 10:07, schrieb Jorge Tornero - Listas:
>>> Hi, Ted, Matthias and all,
>>>
>>> If you enable CRS transform on-the-fly, meter/feet/NM scales can be
>>> shown in WGS84 projects.
>>>
>>> About what Matthias said in
>>>
>>>> Concerning the scale-bar issue. I think, that one should always be
>>>> allowed to show a scale-bar, but that the units need to match with the
>>>> one in the projection, so in the case of WGS84, the units should be
>>>> degrees.
>>>
>>> In my opinion, despite this is completely true from a formal point of
>>> view, sometimes you need scales in 'real world' units just to make
>>> possible for people to understand your maps. For the most of the people
>>> I know that see my little work it makes no sense a scale in degrees (in
>>> fact, they could have it in the grid labels) but a scale in nautical
>>> miles (or whatever) makes sense inmediatly for them, even if it is not
>>> accurate. So, providing that the person who is making the map should
>>> know what he/she is doing, it is nice for the user to have the
>>> possibility to show the scale in whatever units he wants. Maybe it could
>>> be corrected just using a projection (I guess that's the proper way),
>>> but sometimes it leads to "weird" (in the sense of people is used to see
>>> *their geography* in a determinate way) maps which somehow annoy people.
>>>
>>> All the best,
>>>
>>> Jorge Tornero
>>>
>>>
>>>
>>>
>>> El 24/06/14 08:59, Matthias Kuhn escribió:
>>>> Hi Ted,
>>>>
>>>> I don't get a crash here (Linux/latest prerelease). It would be much
>>>> appreciated if you could follow Richards advice for testing/reporting.
>>>>
>>>> Concerning the scale-bar issue. I think, that one should always be
>>>> allowed to show a scale-bar, but that the units need to match with the
>>>> one in the projection, so in the case of WGS84, the units should be
>>>> degrees.
>>>>
>>>> Regards,
>>>> Matthias
>>>>
>>>> On 24.06.2014 08:29, Richard Duivenvoorde wrote:
>>>>> Hi Ted,
>>>>>
>>>>> I'm not on Win, but if possible can you test this with latest release
>>>>> candidates, see
>>>>>
>>>>> http://qgis.org/en/site/getinvolved/development/index.html#location-of-prereleases-nightly-builds
>>>>>
>>>>>
>>>>>
>>>>> and if that one is crashing, please file an issue:
>>>>>
>>>>> http://qgis.org/en/site/getinvolved/development/index.html#bugs-features-and-issues
>>>>>
>>>>>
>>>>>
>>>>> Current dev version has a lot of changes under the hood, but also an
>>>>> awfull lot of fixes!
>>>>> So please test the latest version and let us know if that crashes also
>>>>>
>>>>> Regards,
>>>>>
>>>>> Richard Duivenvoorde
>>>>>
>>>>>
>>>>>
>>>>> On 24-06-14 01:30, Ted wrote:
>>>>>> forgot,
>>>>>>
>>>>>> using Windows OS
>>>>>>
>>>>>> Win 7 Professional x64
>>>>>>
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>> Ted
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, Jun 24, 2014 at 7:27 AM, Ted <tiruchirapalli at gmail.com
>>>>>> <mailto:tiruchirapalli at gmail.com>> wrote:
>>>>>>
>>>>>> Hi Developers
>>>>>>
>>>>>> Encountered a very serious problem, looks like this issue is
>>>>>> there
>>>>>> in 2.x
>>>>>>
>>>>>> Ways to reproduce;
>>>>>>
>>>>>> 1. Add a world boundary shp file in wgs84 (you can use other
>>>>>> files too)
>>>>>> http://thematicmapping.org/downloads/world_borders.php
>>>>>>
>>>>>> 2. Open the print composer, add a new map
>>>>>>
>>>>>> 3. add scale bar
>>>>>>
>>>>>> 4. close the composer, return back
>>>>>>
>>>>>> 5 remove the layer from layer list
>>>>>>
>>>>>> 6. boom, qgis crash
>>>>>>
>>>>>>
>>>>>> hope you can fix this soon, thanks
>>>>>>
>>>>>>
>>>>>> The scale bar issue
>>>>>>
>>>>>> 1. When a file is degree (wgs84), the scale-bar in print
>>>>>> composer is
>>>>>> useless since its trying to use the map unit.
>>>>>>
>>>>>> 2. Its logical that, in map composer its always linear map
>>>>>> unit as
>>>>>> in meter, feet, km, etc
>>>>>>
>>>>>> 3. using qgis in schools and this pose a serious issue, since
>>>>>> the
>>>>>> users dont understand projection etc.
>>>>>>
>>>>>> 4. the expected behavior is, immaterial of underlying
>>>>>> projection the
>>>>>> scale-bar should have the option to use linear map unit,
>>>>>> specially
>>>>>> meters, km, mile
>>>>>>
>>>>>> 5. read in stackexchange, this is a known issue. hope the dev
>>>>>> community can help to fix this one.
>>>>>>
>>>>>>
>>>>>> thanks a lot.
>>>>>>
>>>>>> hurt my fingers, not able to type proper :(
>>>>>>
>>>>>>
>>>>>> cheers
>>>>>> ted
>>>>>>
>>
>>
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