Question

Device FMB3001

According to the documentation AVL 24 is "Speed Value in km/h, 0 – xxx km/h" and AVL37 is "Vehicle speed km/h". What is the difference between the two?

I can see sometimes only one of the codes and reported by the device, sometimes the other one. Sometimes both codes are reported.

Can anyone explain why is this behavior and which value to use for Vehicle Speed?

Answer 1

Hi,

AVL 24 is vehicle speed derived by GNSS, AVL 37 is vehicle speed according to OBDII data. AVL 37 is generally more accurate and better to use because GPS accuracy can vary.

In the configurator you can choose whether you want to use GNSS or OBD/CAN for speed measurement. One or the other or both can be transmitted for a variety of circumstances like GPS jumps reported as movement, starting/stopping tracking due to ignition being turned off/on (also depends on ignition source settings). If you could describe the context in which you see these differences, maybe I can explain more precisely.

Comments

Hi,

Thank you for your reply!

Generally, what I see is either both values being reported in the same record or a record only containing AVL24. This results in more records containing GNSS speed than records containing OBD speed.

Additionally, in the records containing both values, sometimes there are differences, even up to 15 km/h.

That being said, if the OBD value is more accurate I am inclined to use it for speed reading.

However, how do I ensure the device can read the OBD speed value of the vehicle? Can this be seen in the configurator or it can be verified only by testing?