I have a layer with the coordinates of animals from a field experiment. Apart from other attributes the layer also contains the animals' unique ID and a timestamp. I want to know the travelled distance for each individual in a given time frame (e.g. 1 - 5 days).
I tried the points to paths tool but was only able to create paths between all points.
How can I measure the travelled distance and add that information to my attribute table?
Points to path has a 'group' expression optional setting
Use this as your unique Id
Order expression being the timestamp.
Using this, you should get one line for each Id with the Id as an attribute
You can use spatialite.
Make sure you are using a projected coordinate system, if not reproject or the distances will be measured in degrees.
Export the point layer to a spatialite database by right-click - Export - Save features as.
Connect to the database in DB Manager:
Execute this query in the SQL Window, after you have changed tracking to the name of your layer and 3006 to the srid you are using:
with cte as (
select tag_id, datum,
lag(datum,1,0) over(partition by tag_id order by datum) previous_date,
st_distance(lag(geometry,1,0) over(partition by tag_id order by datum), geometry) distance_traveled,
SetSRID(makeline(lag(geometry,1,0) over(partition by tag_id order by datum), geometry), 3006) as geometry
from tracking)
select row_number() over() as id, *, distance_traveled/((julianday(datum)-julianday(previous_date))*86400) as speed_mps
from cte
where distance_traveled is not null
I would have thought that Kasper's answer would be correct, Simon, but I also find that your question is a little confusing. Perhaps you should try the PointsToPaths plugin (note the plural "Paths"). It has added functionality beyond the installed "Points to path" tool.
In particular, try the plugin's "Line per Vertex" checkbox. For more details on PointstoPaths see my previous answer.
