The mystery of the 12 second latency in the dynamic response of the EM406 GPS is solved.

Recently, I stirred up a debate about whether or not the EM406 has a 12 second latency or not. A few of us were seeing a 12 second latency. The majority of EM406 users were not seeing it.

It turns out that the dynamic performance of the EM406 depends on which interface you use, NMEA or binary. If you use binary, there is a 12 second latency, then a 3 second "smoothing" transient.

If you use NMEA, there is a smoothing transient only. The NMEA interface to the EM406 provides dynamic performance as good as the LOCOSYS or the ET312.

It is my speculation that "track smoothing" is turned on in the EM406 for the binary interface, and either it is always on, or I have not figured out how to turn it off. If anyone knows how to turn track smoothing off in the binary interface for the EM406, please let me know so that I do not have to scrap my binary interface and start over on a NMEA interface.