I have a CSV file with WGS84 trackpoints and visualizing them with QGIS textplugin works fine. The log interval is 1sec and I like to get the current speed to get a visual feedback, how fast the vehicle was between two points (so distance/time). Any idea how I can realize this with a style?
I can imagine a solution using a SpatiaLite database provided each trackpoint has some sequential id number. First import your CSV file into spatialite (plenty of sources available to explain this step) then make it a spatial layer: (I assume the CSV has columns longitude, latitude for the GPS locations, and a column 'id' with the sequential numbering of the trackpoints)
SELECT AddGeometryColumn('trackpoints','geometry',4326,'POINT','XY'); UPDATE trackpoints SET geometry=MakePoint(longitude, latitude, 4326);
Now you have a spatial point layer with each point numbered along the track. Add a column to contain the distance from each point to the next one:
ALTER TABLE trackpoints ADD COLUMN dist real;
Now to get the distance between each pair of points, make a line segment from a pair and use the GeodesicLenght() function to get distance in meters. Here's how it would be done:
UPDATE trackpoints SET dist=( SELECT GeodesicDistance(MakeLine(trackpoints.geometry, tp1.geometry)) FROM trackpoints AS tp1 WHERE tp1.id = trackpoints.id+1;
Now the dist column should contain for each point the distance to the next. Finally. divide dist by the time interval between points, and you should have the speed...