  Context: Studying the motions on the solar surface is fundamental for
understanding how turbulent convection transports energy and how magnetic
fields are distributed across the solar surface.
  Aims: From horizontal velocity measurements all over the visible disc of the
Sun and using data from the Solar Dynamics Observatory/Helioseismic and
Magnetic Imager (SDO/HMI), we investigate the structure and evolution of solar
supergranulation.
  Methods: Horizontal velocity fields were measured by following the proper
motions of solar granules using a newly developed version of the coherent
structure tracking (CST) code. With this tool, maps of horizontal divergence
were computed. We then segmented and identified supergranular cells and
followed their histories by using spatio-temporal labelling. With this dataset
we derived the fundamental properties of supergranulation, including their
motion.
  Results: We find values of the fundamental parameters of supergranulation
similar to previous studies: a mean lifetime of 1.5 days and a mean diameter of
25~Mm. The tracking of individual supergranular cells reveals the solar
differential rotation and a poleward circulation trend of the meridional flow.
The shape of the derived differential rotation and meridional flow does not
depend on the cell size. If there is a background magnetic field, the diverging
flows in supergranules are weaker.
  Conclusions: This study confirms that supergranules are suitable tracers that
may be used to investigate the large-scale flows of the solar convection as
long as they are detectable enough on the surface.
