Navigation technology for posting speed limit

[Eusbls]

What technology is used to display the speed limit? Usually it is pretty accurate, but I recently Driving on (a very widely used road) and the speed limit displayed was over by 15 miles.

 

[Beefer]

GPS map info.

 

[MrMegadeth]

Part of the underlying data in the maps.

some cars, e.g. Volvo, use the camera to read the signs and show them or change the speedlimit. The Genesis does not do this. Use Waze or Google if you want real, up-to-date info.