If your not bean counting for a commercial product you can take a look at particle filtering, its like a real-time monte-carlo simulation.
The location estimate in NEMA is also heavily filtered and referenced to its utc time estimate (PPS). Conceivably could be filtered to a bandwidth of Fs/2, 500 milliHz. On Thu, Jul 21, 2016 at 12:00 AM, Chris Albertson <[email protected] > wrote: > I might have been the one who brought up the problem of the NMEA > message not being right on the UTC send tick. But now I'm thinking > of another problem this might create. It is slightly off topic > because it has to do with location. > > Let's say I have a mobile robot (or a self driving car) that wants to > know where it is. I have a three axis gyro, three axis accelerometer > and a three axis magnetometer (acting as a magnetic compass. I also > have rotational encoders on the wheels to count millimeters of travel. > In theory I can dead recon from any known point but all of those > sensors drift or are otherwise imperfect. So I add GPS. GPS's > problem is it's on order 10 meter level accuracy and I need > centimeters or better. The combination works. Each sensor makes up > for the faults in the others. > > But up until now I have forgotten that the NMEA location data is > likely some tens or hundreds of milliseconds old before it is output > on the wire. This "noise" was hidden in the large location > uncertainty inherent in GPS. Accounting for this should make my GPS > more accurate. > > Now an off topic question that I bet many in this group can answer. > I'm a total novice when it comes to Kalman Filters. I need to > expertly combine all this data using one. Anyone got a good > (hopefully on-line) tutorial or a cheap book on Amazon. (yes I used > Google, got 1,000+ hits) I'm trying to do this myself and have found > I forgot most of my Linear Algebra (it's been 30 years) and I doubt I > ever really understood Kalman Filters completely > > On Tue, Jul 19, 2016 at 10:20 AM, Mark Sims <[email protected]> wrote: > > I ran some tests on the message timing of some V.KEL gps receivers in > both NMEA and binary mode. These receivers are the cheapest ones I have (3 > for $15 - $20, shipped). They use a SIRF III chip and have an on-board > ceramic patch antenna. They performed amazingly well. No problems > tracking sats indoors in a very poor location. Message jitter was less > than 20 msecs peak-peak, standard deviation less than 2 milliseconds. > ADEVs at tau 10000 after an overnight run in NMEA mode (hardware serial > port) were in the 1E-7 range! They also have a 1PPS signal on the > connector so no need to go digging for a place to bodge on a wire like with > some of the other cheap GPS modules out there. > > > > V.KEL also makes a Ublox based version of the module (around $22 for > one)... mine reports that it has a Ublox 7 chip, though V.KEL's part number > implies that it a Ublox 6. > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
