More rational Scales in composer and support for nautical miles on them

[jtornero]

This is a little effort to make QGIS more usable for people related to the sea and marine scientists in particular, but also to provide a more rationale graphical scale system for the composer.

Scales in previous versions look somehow strange, because number of automatic units are sort of random. I propose to make more rationale scales. For instance, an automatic scale will be always be sort of "decimal" multiples, like 10, 20, 30or 25, 50, 75 or 5, 10, 15; The maginitude order of the quantity of the unit displayed in the scale is proportional to the width of the map but also is always multiple of ten.

I've tried to follow the schema provided in the previous code, making it possible to use multiples of the base units (meters and kilometers, for instance). also for imperial units; because I'm a metrical system user (except for nautical miles), I don't know if it's practical to use feet and miles, so please take a view on it, maybe it's better to use feet/yards/miles. In the case of Nautical miles, I don't know about practical uses of submultiples, but the same schema could be implemented.

Best regards,

Jorge Tornero

[gioman]

@nyalldawson @mhugent

[nirvn]

@jtornero would be nice of you to have a look at http://hub.qgis.org/issues/9050 (unable to user non-degree units with scale bar when project's CRS is set to wgs84), seems the issue overlaps with some of the improvements your trying to achieve. Good luck :)

[jtornero]

@nirvn @gioman
Well I've tested my code against what you relate in issue 9050; in fact in fact I opened a feature request http://hub.qgis.org/issues/9065 where I suggest that both issue 9050 and my proposal could be somehow connected. My code works well when OTF projection is on, as you can see in the attached screenshot.

When I use a projected CRS, like ED50 / UTM zone 30N (EPSG:23030), the scale gets mangled and nonsense, wrong magnitudes are shown in the scale.

But in both cases, it looks that if you choose the right numbers, scales in map units (degrees) look good. In the case of Map Units, choosing 1 both for map units by bar unit and segment size renders nice scales in degrees. But for scales in feet/meters/NM it doesn't work.

I'll try to do my best with C++ but I can't promise much. I'd love if someone gets involved with this.

Best regards,

Jorge Tornero

[jtornero]

Sorry about the multiple commits... not a git advanced user... just wanted to notify you

[mhugent]

assigned to @mhugent

[nirvn]

@jtornero thanks for looking into this. It seems to me that the user-friendly behavior here would be to disable non map-based unit on scale item when OTF is off. Or at least add a label mentioning that the scale item's meter unit won't work under non-meter projection when OTF is off.

[nyalldawson]

@jtornero Thanks for this valuable work -- sorry it's taken so long to review. I've manually merged a modified version of this commit to master!

[jtornero]

@nyalldawson Sorry for my little git/developing skills but... does it mean that the feature has been incorporated to qgis and will be available on 2.2 and I can consider the work done???

[NathanW2]

I does indeed.

• Nathan

On Tue, Jan 14, 2014 at 8:04 AM, Jorge Tornero notifications@github.comwrote:

@nyalldawson https://github.com/nyalldawson Sorry for my little
git/developing skills but... does it mean that the feature has been
incorporated to qgis and will be available on 2.2?

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Reply to this email directly or view it on GitHubhttps://github.com//pull/995#issuecomment-32216676
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