QGIS quickest method of calculating distance between multiple points in one layer?

Question

Using Qgis 2.18.3, I am looking for the quickest method of calculating the aggregated distance between multiple points. As the Crow flies would be enough...

I have a point layer in a small area. They have unique and incremented ID's. (in my case these are stops of a truck)

I was using the Points to path plugin to create lines. Then using $length to calculate the length and then basic statistic to aggregate the length. I could build a model to automate this a little. The thing is that I have hundreds of those seperate point layers...

Is there an other method which is quicker?

Answer 1

You could also make a shell script for all your files so you don't have to sit around waiting for QGIS to be ready. In this example the points are shape files and saga_cmd and ogr2ogr is used.

#!/bin/sh

for i in *.shp

do
    f=$(echo $i| cut -d'.' -f 1) 
    saga_cmd shapes_lines 1 -LINES ${f}_line.shp -POINTS ${f}
    ogrinfo ${f}_line.shp -sql "ALTER TABLE ${f}_line ADD COLUMN length integer(5)"
    ogrinfo ${f}_line.shp -dialect SQLite -sql "UPDATE ${f}_line SET length = ST_Length(geometry)"
done

Then you'll get polyline shape file for each point file with a new column showing length of the line. You could also add options to saga_cmd with order of points etc.

Answer 2

You could create a custom script (or a model but I prefer script) which runs the Field Calculator and the Convert points to lines to create an output of a single line joining all points with a Length field containing the aggregated length.

You can create one from:

Processing Toolbox > Scripts > Tools > Create new script

Then use something like the following:

##Example=name
##Point_layer=vector point
##ID_Field=Field Point_layer
##Result=output vector

output_fieldCalculator = processing.runalg("qgis:fieldcalculator", Point_layer, 'Separate', 1, 10, 0, True, '1', None)
output_pointToLine = processing.runalg("saga:convertpointstolines", output_fieldCalculator['OUTPUT_LAYER'], ID_Field, "Separate", None)
output_fieldLength = processing.runalg("qgis:fieldcalculator", output_pointToLine['LINES'], 'Length', 0, 10, 2, True, '$length', Result)

Make sure to save the script into your /.qgis2/processing/scripts directory.

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Example:

When you run the script, you can select the point layer and the ID field:

Result:

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Note: The "Separate" field is only used for the SAGA tool to create the line correctly.