Calibrated airspeed (CAS) is the speed shown by a conventional airspeed indicator after correction for instrument error and position error. Most civilian EFIS displays also show CAS. At high speeds and altitudes, calibrated airspeed is further corrected for compressibility errors and becomes equivalent airspeed (EAS).
When flying at sea level under International Standard Atmosphere conditions (15°C, 1013 hPa, 0% humidity) calibrated airspeed is the same as equivalent airspeed and true airspeed (TAS). If there is no wind it is also the same as ground speed (GS). Under any other conditions, CAS may differ from the aircraft's TAS and GS.
Calibrating the airspeed is one thing I can't do, it is related to the builder choice to place the Pitot tube. One have to flight runs in still air and compare GPS and airspeed to see if it need correction or find a better place. On my DG there is no integration issue. I didn't have any issue either with the low speeds on my EasyGlider (low 30 km/h), Pitot was in the nose. Instrument calibration is done when the module start for a few ms. The Pitot need to be protected during this period, this is the zeroing.
I think I'll have the time to race with a pilot who use my system late August. I'll use my FrSky/android smartphone App and he will use the PDA/2.4Ghz radio modem I did before. We will race at a slope, arround a 5 or 6 waypoints on few laps . Waypoints windows will vary in altitude so we can have a 3D race. My budy will use either a 5m Vortex or a 5m Pegase. He sure will win because he is a very tallented pilot