NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Error ellipse proportions
From: Robin Jouan
Date: 2017 Jun 12, 02:08 -0700
From: Robin Jouan
Date: 2017 Jun 12, 02:08 -0700
Regarding the accuracy of a n sight fix, a double approach can be considered:
- a posteriori, through error ellipse or circle projection into a local plane template (which is mostly geometric);
- a priori, through DOP computation (which is mostly algebraïc).
DOP concept was introduced first for LORAN navigation, and cannot be avoided with GPS-GNSS, but also with hybrid navigation.
I published some basic results about celestial DOP in 2004. See the attached slide for a 3 sight fix.
We can check that the optimum is flat around a regular azimuth shift of 120°, with an HDOP of 1.155.
Furthermore, we see that we loss an order of magnitude in accuracy if the azimuth angles are less than 30°.
BR
