Broadcast Orbit File Instead of Rapid?

Jim Frame

Well-Known Member
[Note that I could have sworn I posted this earlier today, but I don't see it showing up on the thread list, so...]

I submitted a file this morning for an observation taken yesterday, and the result used -- as expected -- the broadcast orbit, as the rapid was not yet available. However, I submitted the same file several times throughout the day, well after the rapid orbits went live, but the results still show that the broadcast ephemeris was used. Am I overlooking something?
 

Jim Frame

Well-Known Member
Why would DPOS *not* be programmed to take advantage of the rapid orbit data? That would be throwing away free error reduction.
 

Jim Frame

Well-Known Member
The advantage lies in reducing the SV positional error from about 1 meter to about 2.5 cm. That's a big advantage in my book.
 

Alexey Razumovsky

Well-Known Member
JAVAD GNSS
5PLS
It deals less then 1 mm for Double Difference postprocessing in a range under 100 km. Moreover I do not trust rapid orbits. In PPP we use precise ephemeris and get a good result.
 

Duane Frymire

Active Member
It deals less then 1 mm for Double Difference postprocessing in a range under 100 km. Moreover I do not trust rapid orbits. In PPP we use precise ephemeris and get a good result.
Interesting Alexey, I hadn't heard this before. Are you saying the broadcast has a known/fixed error estimate of predicted location; the rapid is an unchecked measurement of location that could contain errors greater than broadcast and/or mistakes; the precise is the rapid having been checked and errors propagated, mistakes removed? Have you found large errors/mistakes in position from rapid orbits? Not sure if I have my questions correct, just trying to learn more about it.

I replied to wrong message, I was referring your above post about trouble, chaos, confusion.
 

Alexey Razumovsky

Well-Known Member
JAVAD GNSS
5PLS
I meant that Internet source of rapid orbits migrated several times during DPOS life. Different source publish rapid orbits that does not match each others. They update date many time during a week. It's difficult to manage these data. The benefit of rapid orbits is too small. Even 'single difference' eliminates impact of 2 meters orbit error to 1 mm in baseline accuracy.
 

Duane Frymire

Active Member
I meant that Internet source of rapid orbits migrated several times during DPOS life. Different source publish rapid orbits that does not match each others. They update date many time during a week. It's difficult to manage these data. The benefit of rapid orbits is too small. Even 'single difference' eliminates impact of 2 meters orbit error to 1 mm in baseline accuracy.
Thanks for the explanation Alexey!
 

Jim Frame

Well-Known Member
I've had to update my links to the IGS orbits a couple of times in the last year or two, so I understand the frustration. With regard to the accuracy, I do mostly static work and don't like to give up any convenient opportunity to beat down the error sources, so I mostly use the rapid orbits. (I can almost always wait a day to get the rapid, but I often can't wait 2 weeks for the precise.) For RTK I appreciate the insignificance of a 1-mm benefit, but since DPOS is also used for static observations, it seems like a lost opportunity.
 
Top