5

Fairly new to QGIS and searching a method to graphically align my point symbols in the direction of the vector. The symbol represents a water valve in an irregular shape in close proximity to a vector water network--is there a way to align each symbol adjacent/ horizontal to a water network vector layer?

6

Yes, but it's a manual method I read about.

In QGIS 2.0.1 you can set the point symbol to be rotated based on an angle(integer/double) in a field.

Have a look at What is the best way to represent bridges using a point vector layer in QGIS?

In that example, "bridges" which are represented as point features and with a custom symbol on the map are rotated based on a value in a field.

Getting Your Bearings (automatic method)

This is basically a spatial join from a line attribute (the bearing) to the nearest point feature.

lines and points in the flesh

1.) Split line feature into segments based on nodes/vertices with v.split.vert in the processing toolbox (GRASS required):

v.split.vert - splitting based on "2" vertices per segment

2.) Use QGIS field calculator on split_lines to get the bearing for each segment (start editing layer before field calculator can be used):

For convenience: (atan((xat(-1)-xat(0))/(yat(-1)-yat(0)))) * 180/3.14159 + (180 *(((yat(-1)-yat(0)) < 0) + (((xat(-1)-xat(0)) < 0 AND (yat(-1) - yat(0)) >0)*2)))

qgis field calculator used to get bearing of a line segment Stop editing and save changes to retain your newly created [bearing] field.

3.) Use Distance to nearest hub in the Processing toolbox and set the split_lines as the Destination Hubs Layer with [bearing] in the Hub Layer Name Attribute. Measurement Unit can safely be ignored in this example.

Using "Distance to nearest hub" to attach attribute from lines to points in QGIS

4.) Create a new Decimal Number type field in the points_with_bearings file called [bearing] to convert the [HubName] field from a string. [HubName] and [HubDist] can be deleted if they're not needed.

Stop editing points_with_bearings and save changes.

qgis field calculator

5.) Go to the Style tab in the Layer Properties window for the points_with_bearings layer and set [bearing] as the Rotation Field.

setting a point rotation value based on a field in QGIS

rotated points aligned with nearest line segment rendered in QGIS

References:

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.