i am using insfilterNonholonomic filter and i wanted to ask how to conver my gps speed to velocity in local NED coordinates

i am using insfilterNonholonomic filter and i wanted to ask how to conver my gps speed to velocity in local NED coordinates my gps data are "lla , speed ,course, horizontal position accuracy". and how to find velocity accuracy ?

Answer 1

[Brian Fanous]

Assuming your device is traveling on the ground (no Z direction velocity, Z position == 0) and we are working in NED....

Your speed is the vector magnitude of your x and y velocity. Your course is the direction of the speed.

speed = sqrt(velx*velx + vely*vely)

course = atan2(vely, velx)

Your velocity accuracy is a function of your GPS device. Perhaps look at the device specification. The tune() method can help you determine the optimal value if you have a ground truth trajectory.

[Junhui]

Hi there: I am also using insfilterNonholonomic filter to predict system trajectory. But what if I need to account for altitude change. How would that affect the formula to compute gps velocity (assuming system altitude varies only a little bit as compared to latitude or longitude of system)? Thanks...