[Qgis-user] Generate Text Labels for USA National Map?

[Bernhard Ströbl]

Hi,
just some thoughts:
- I assume you want to have QGIS create label texts for all your data in 
one go. 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.)
- 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
- Thus the label text is only within QGIS, export may be possible with 
dxf-export
- 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?
- There will be map extracts with "many" labels (city centres) and map 
extracts with "few" labels (boondocks).
- 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)
- 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)
- points are vector features, too, so there is no real difference 
between labelling points, lines or polygons.
- 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#

hope this helps
Bernhard


Am 05.07.2017 um 09:11 schrieb Jeshua Lacock:
>
> Greetings,
>
> I currently have all the base layers for a 1:24k topographic national map of the US worked out. Many many terabytes of data currently all in GRASS.
>
> The last hurdle I have is to figure out the best way for labeling vector features (hydro, roads, contours) and point text (mountain summit names, place names, etc.).
>
> Based on my research so far, it seems that QGIS might be one, if not the most powerful open source software for GIS text labels.
>
> A few questions, if I may. I am new to QGIS so please forgive me if I am asking something that is obvious.
>
> 1. Is text that is created with the Rule-based labeling feature exportable, or is it is only for display in QGIS? If it is exportable, what formats can it be exported to? Anything besides raster?
>
> 2. Would it be possible to generate labels for the entire nation (millions of labels) with the rule-based labels, or would I have to do it in many sections?
>
> 3. For point text, are there any algorithms that help prevent labels from overlapping each other? Such as those outlined at: https://en.wikipedia.org/wiki/Automatic_label_placement
>
> 4. Can point text be used with the rule-based labeling or is it only for vector data with attributes?
>
> If anyone has undertaken a similar task as I am researching, I would certainly appreciate any and all feedback and advice.
>
>
> Many thanks,
>
> Jeshua Lacock
> Founder/Engineer
> <3DTOPO.com>
> GlassPrinted.com
>
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