lineqgisvertical
I create a new shapefile layer as a line. Then I activated editing mode and want to draw vertical or horizontal lines with add feature but holding shift does not allow to draw a horizontal or vertical line (I used QGIS 2.14.4).
How can I draw horizontal or vertical lines as a shapefile?
You can use a QGIS expression in the label expression.
"Date" || '\n' || "Size" || '\n' || "name"
You can even wrap the expression over multi lines to do the same thing
"Date" || '
' || "Size" || '
' || "name"
Note the ' at the end and start of each line. The first is clearer with its intentions so I would use that.
If one of the fields can contain NULL values, you can use concat() instead of || concatenator:
concat("Date",'\n',"Size",'\n',"name")
First, you don't really want to make the lines to overlap, but only to reflect in the attributes the number of flights that are using the same path. This can be done following these steps:
Make sure you create a new column for your lines, call it "flights" and use the value 1 for all of them. I used the name "Count" which is not the best.
Then, perform a buffer operation with the desired proximity, you will have to play with the distance that you consider appropiate for your analysis: (my QGIS is in Spanish but I am sure you can figure it out)
Then, you have buffered lines that are most likely touching each other, like sausages. Your last step is to perform a spatial join, under vector, data management menu. Use the options intersect, as follows:
Make sure you add the summary option with the sum. The result will be a new column in every attribute, adding the number of other flights that are intersecting. If the lines have an ID you can join this new column to your original lines, or you can turn the buffered polygons back into lines.
If you want to simplify and remove the extra lines is a different problem, but I hope I could have helped you to start at least.
Best Answer
The CADTools plugin has a feature named
Orthogonal Digitizing.While in editing mode of a line or polygon layer, holding ctrl allows to draw orthogonal lines.
Furthermore, the QAD plugin snaps to the horizontal or vertical axis when drawing a
LINEobject.