get lat/lon values of every start and end point of polyline

Question

I have a polyline shapefile with 166 different line features. How would one populate the attribute table with x and y values of the start and end points of each line?

Answer 1

You have your four columns: X-start; Y-start; X-end; Y-end. Using the field calculator for each column update using:

$x_at(0)
$x_at(-1)
$y_at(0)
$y_at(-1)

This asks for the coordinate at the start of the line (the zero) and the end of the line (the negative one). This will provide you with a decimal latitude and longitude, so ensure the columns are floats.

EDIT: Thanks to the_darkside's comments please note this won't work on multi lines, due to the multiple beginnings and ends.

Answer 2

In the attribute view create your new columns as decimal (floats).

Then enable editing, and use expressions to update the columns.

To get the latitude (x-coordinate) of the start of a line feature, use the expression x_at(0). To get the end of a line feature use x_at(-1). Repeat for your longitudes (y-coordinates). You select the column, type in the expression, and hit "Update All".

This assumes your data is in lat-long (ESPG:4326 most likely). If not, transform to that and save, or transform within the expression. Here my data is in EPSG:27700 and I want lat-long (EPSG:4326):

x(
start_point(
 transform( $geometry, 'EPSG:27700', 'EPSG:4326' ) 
 )
 )

Replace x with y and start_point with end_point for your four columns.