Hi Jeshua,
I cannot advice you in how you can achieve your goal :-(
but would like to give some more answers and explanations
Am 05.07.2017 um 23:41 schrieb Jeshua Lacock:
On Jul 5, 2017, at 2:32 AM, Bernhard Ströbl <[email protected]> wrote:
- I assume you want to have QGIS create label texts for all your data in one go.
Hi Bernhard,
That would be ideal.
If that is the case this is a misunderstanding of what labels are (in QGIS):
QGIS creates (and places) the labels at run-time for the map extract currently
on display. Labels thus are no features of their own (GIS only knows
points/lines/polygons) but a way to display GIS features (like e.g. color,
outline etc.)
I was afraid that might be the case. :’(
- This means the labels are valid for this particular map extract in this
particular scale. E.g. imagine a lake (= one polygon) that expands on two map
extracts, it will be labeled in both => one feature, two labels
Understood. I was thinking of generating text at say 4 different scales.
- Thus the label text is only within QGIS, export may be possible with
dxf-export
Is it possible to script or automate setting the view extents and exporting?
(I assume) you may of course use a script that automatically creates map
extracts and exports the labels but you will face the problem of
multiple labels for the same feature (lake example, steet that stretches
over several extracts). If you want labels for an arbitray map extract
IMHO you cannot produce the labels in advance but have to label at run time
- IMHO it doesn't make sense to try to use the labels outside of QGIS; what is
your intended final result? Which software are you planning to use for creating
your final result?
Initially it will be a custom iOS app (with planned android and possibly
desktop computer versions). I might offer printed hard copies too at some point.
This sounds like arbitrary map extracts, so your app should label at run
time; Andreas already commented on that more sophisticated than I could.
- There will be map extracts with "many" labels (city centres) and map extracts with
"few" labels (boondocks).
Yes, that is why I was looking for something that already can deal with crowded
text versus re-inventing the wheel.
- QGIS can prevent overlapping labels; in placement you can assign a priority
to the labels of this layer (so e.g. rivers are always labeled whereas streets
only if not in conflict with rivers)
Nice.
- The rule based labelling works _within_ a layer; a rule is a logical
statement about the feature to be labeled. The logic can be based on the
feature's attribute values or geometry (e.g. label only lakes larger than x)
So essentially, I would want all the text on one layer - so point text doesn’t
overlap with say road or river text, correct?
No, the rule-based labelling sports rules that decide _if_ (and how) a
feature within a layer should be labelled; think of a layer containing
street lines:
Rule 1: Label all major streets at all scales with 10pt bold
Rule 2: Label minor streets only at larger scales with 8pt normal
Rule 3: Do not label residential streets at all
QGIS' labelling algorithm will then collect all labels from all layers
delivering labels for the map extract to be rendered and decides if
labels need to me moved or suppressed because of the settings (e.g.
label priority) to prevent overlapping labels. At this point the rules
have already been applied as the rules deliver a set of labels for a
particular layer.
If you consider your river labels more important than your road labels
simply give them a higher priority.
To be honest: In my experience the automatic labelling works really well
and satisfactory for 99% of the cases, BUT in case you want a certain
"perfect" print out you need to manually adjust or suppress certain
labels because creating a map is a design work and there are always
cases where your notion of the result differs from what the algorithm
provides (e.g. have that highway labeled although the label can only be
placed on the bridge and river labels have a higher priority).
- points are vector features, too, so there is no real difference between
labelling points, lines or polygons.
Great.
- Be sure to have read the doc:
http://docs.qgis.org/2.14/en/docs/user_manual/working_with_vector/vector_properties.html#labels-menu#
Thanks for the link and help!
Best,
Jeshua Lacock
Founder/Engineer
<3DTOPO.com>
GlassPrinted.com
regards
Bernhard
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