Adding Timestamp to attribute table in QGIS

Question

I have the project where, in one part of it, I need to add the timestamp to uniform generated points along the line (road, in my project). There is a road and uniform distributed points on it, which represent the trajectory of a car. Each point represents the car's location at certain time on the road.

How can I add dynamic timestamp that if, let's say, I need to decrease the speed of the car, the timestamp of the certain point will change as well?

Answer 1

Using the QGIS field calculator you can create an expression on a Time type field, with the speed as a variable. Changing the speed and re-calculating the expression will adjust the times accordingly. For the example I used 14 m/s (approx 50 km/h) as the initial speed and 20:00 as an arbitrary start time, the points are 250 m apart (created with the Points along Geometry tool on a line. The tool automatically adds a distance column to the point layer).

Assuming distance is meters and speed is meters per second:

with_variable('speed', 14,                             -- set the speed variable
    with_variable('start_time', make_time(20, 0 ,0),   -- set a start time variable
        CASE 
            WHEN "distance" = 0                        
            THEN @start_time                           -- input the start time at zero distance
            
            ELSE @start_time + to_interval(to_string("distance" / @speed) || ' seconds')  -- add the elapsed interval (distance/speed) to the start time and calculate the remaining rows 
        END
    )
)

Change speed to 20 m/s:

Note: for the labels in the images, I removed the milliseconds component from the time.