ROS Answers: Open Source Q&A Forum - RSS feedhttps://answers.ros.org/questions/Open source question and answer forum written in Python and DjangoenROS Answers is licensed under Creative Commons Attribution 3.0Fri, 22 Nov 2019 04:43:10 -0600How to find reasonable values for NavSatFix position covariance?https://answers.ros.org/question/338310/how-to-find-reasonable-values-for-navsatfix-position-covariance/ I have a GPS sensor whose driver doesn't report any info on positioning accuracy. Basically, what we have is lon, lat, alt only.
Is there a way to make up reasonable values for the position covariance in order to feed the data into a Kalman filter? (I assume that robot_localization's EKF/UKF doesn't insert useful default values in case the covariance is reported all zero...)
I'd be interested in any insights, from ballpark estimates to calibration methods or anything else.Fri, 22 Nov 2019 03:54:54 -0600https://answers.ros.org/question/338310/how-to-find-reasonable-values-for-navsatfix-position-covariance/Answer by davekroezen for <p>I have a GPS sensor whose driver doesn't report any info on positioning accuracy. Basically, what we have is lon, lat, alt only.</p>
<p>Is there a way to make up reasonable values for the position covariance in order to feed the data into a Kalman filter? (I assume that robot_localization's EKF/UKF doesn't insert useful default values in case the covariance is reported all zero...)</p>
<p>I'd be interested in any insights, from ballpark estimates to calibration methods or anything else.</p>
https://answers.ros.org/question/338310/how-to-find-reasonable-values-for-navsatfix-position-covariance/?answer=338320#post-id-338320You could estimate the covariance matrices using trial and error. If not outrageously wrong, the covariances will converge eventually if my memory serves me right. Another method would be to apply the Autocovariance Least-Squares (ALS) technique (or possible other techniques) to estimate the noise covariances directly from sampled data. A quick search resulted in this paper which talks about the technique: [Paper Link](https://www.sciencedirect.com/science/article/pii/S0959152407001631)Fri, 22 Nov 2019 04:43:10 -0600https://answers.ros.org/question/338310/how-to-find-reasonable-values-for-navsatfix-position-covariance/?answer=338320#post-id-338320