Integrating SPAN with Wheel sensor

We have defined a generic interface that can accommodate any style of sensor that provides a distance traveled input. The SPAN filter accepts wheel sensor updates in the form of the WHEELVELOCITY command. The basic idea is that an external hardware device keeps track of the number of pulses that occur between PPS signal. When the PPS fires this device sends a message back to the receiver with how many ticks have occurred which effectively translates to a distance traveled. All SPAN variants accept the WHEELVELOCITY command, which supplies wheel sensor data to the SPAN filter at 1 Hz. For LN200 and HG1700 users, they must create and send the WHEELVELOCITY command. This usually requires an intermediate piece of software/hardware which is up to the user to develop. Here is the link to our application note about using a wheel sensor with SPAN: http://www.novatel.com/Documents/Bulletins/apn036.pdf