I did a simple math and derived frontal acceleration from speed data (just subtract two consecutive speed values and divide to time interval, then convert to G-value) to compare with screen outputs. I choosed two points: with bigger acceleration and bigger braking.
Acceleration: Both Dashware and RR speed data gave close results - DW 0.464G, RR 0.484, but acceration outputs on the screen differs: DW gives almost exact 0.46G, RR more than two times smaller 0.19G (pictures 1 and 2).
Braking: Again, deceleration, calculated from speed data are comparable: DW 0.84G, RR 0.76G, but screen outputs differs: DW 0.73G, 10% difference from calculated, and RR 0.23G, more than three times less than calculated from speed (pictures 3 and 4).
Here we see, that frontal acceleration values, clculated from DW and RR data are in good agreement. Dashware output on the screen differs within 10%, but RR data differ 2 or 3 times. That shows, that DW and RR both use accelerometer sensor data, but Dashware output is much closer to the results, given from speed data.
Initially I had intent to do similar calculation with lateral acceleration data too, but quit. The math behind is not too complicated but it is time consuming for calculations by hand. There latitude/logitude data have to be converted to coorinates on the surface (which in program is anyway done for track map). Then three consecutive points are approximated as part of circle and calculated radius of this circle. Then by formula A=v*v/R (where v is linear speed and R calculated radius) we will have lateral acceleration A. But It will take too much time using just calculator.
CONCLUSION (so far): I do not know, what causes this big difference in accelerations data, but RaceRender acceleration data look to me incorrect and these comparisons and calculations are not only reasons. Therefore until I will know reasons of this difference and have a way to fix this problem, I unfortunately have to use a workaround - use Dashware to extract GPS data from video to scv file and then use these csv data with RaceRender