SBAS Tracking?

At least from a topcon stand point . SBAS when setup uses 1 or 2 sat to fix to around 1 to 3 feet . I think it's the waas satallites .Use it for recon maybe. That's what the GIS folks use to do their work..

Ashtech Receivers Can Use SBAS For Ranging

SBAS broadcast on the L1 frequency so a range to the almost stationary satellite can be included in the mix for positioning. The methods could be used by any receiver and I believe the right to that specific algorythm may already be sold to other's.

Paul in PA

There are tube videos setting up SBAS on a Topsurv collector . Look up Hollaman
Will give you Gis quality readings and tell you fixed like you are using RTK .

Ashtech Receivers Can Use SBAS For Ranging

Hi Paull. The Epoch 35 is sold under the Spectra Precision brand, which is owned by Trimble who also owns Ashtech. The documentation for the reciever states that it can track GPS, Glonass and 2 SBAS satellites and manaul states that the SBAS tracking setting is specific for the Epoch 35 reciever. If this is the case would one want SBAS tracking toggles on for VRS? ...or would it only apply when you are using a base and rover setup that were both utilizing the SBAS signal/ satellites?

Thanks
Kelly

Ideal To Have It On For Both

but it is my understanding that it can still aid the rover in a faster fix. No actual experience. Just what I learned from following all the new developments.

Paul in PA

Ideal To Have It On For Both

Thanks Paul, I'll try turning it on. It does seem like it takes longer than necessary, sometime 10 to 15 mins, for initial fix with good conditions.

Ideal To Have It On For Both

I don't know what the SBAS tracking would do on an Epoch 35. I think that receiver has a Novatel board in it and where they are with that, I don't know.

When Ashtech (then Thales Navigation) introduced the Promark3, SBAS tracking was to be an option, used in both static and RTK functions. When you download static data from a Promark3, you get the usual Ashtech B, D & E files, the B file containing the range data from the satellites, the D file containing the Receiver ID and setup information and the E file containing the ephemeris data broadcast by the satellites. You also get a W file that contains data from the WAAS satellites (the US SBAS system) which can be ranged and included in your post-processed solutions.

The Promark3 also uses this data in its RTK process. It is my understanding that the Ashtech Z-Max and Promark 500 also include SBAS data in their RTK solutions.

I do not know if anyone else does or not.

Ideal To Have It On For Both

I dont know. The Survey Pro manual speaks about toggling the setting specificaly for the Epoch 35. When SBAS tracking is toggled on the receiver shows a W on the screen until it is set then it shows a A, D or F depending if the unit is autonumous, floating or fixed.

There Is No Technology Block To SBAS Ranging

Receivers already can receive L1 signals. It is a matter of the additional algorythm to turn that signal into range distances. Ashtech or other board should make no difference.

What I have not found out is how the receiver calulates the SBAS position. Perhaps each SBAS satellite broadcasts it's own ephemeris.

What the future bodes is amazing, SBAS satellites broadcasting an L1 and L5 signal. Whether or not there are enough GPS satellites broadcasting L5, because of the positional stabilty of the SBAS satellites L1/L5 can be resolved on 1 or 2 SBAS satellites independant of the L1/L2 GPS.

In the future the limit on SBAS can be increased to 3 or 4. An ideal configuration is 1 each, SE, S and SW. Then add in a 4th on a geosynchronous orbit over the center of the USA heading for the North Pole. This geosynchronous orbit does not have to be circular. A highly elliptical orbit with apogee over Kansas would keep a satellite in view over the US for 12 hours of a 24 hour circuit. When this comes about the central geostaionary satellite becomes redundant. Currently SBAS are payloads on typical communications satellites. I believe the geosynchronous would be dedicated but that is not neccessary. The SBAS package could also be a payload on a US weather satellite. Some of this may have to wait until the US expands GPS beyond 32 PRN numbers.

Paul in PA