[OSM-newbies] Detect WAAS/EGNOS mode

Andy Robinson (blackadder) blackadderajr at googlemail.com
Fri Apr 25 00:32:02 BST 2008


Jeffrey Martin
>Sent: 25 April 2008 12:07 AM
>To: newbies at openstreetmap.org
>Subject: Re: [OSM-newbies] Detect WAAS/EGNOS mode
>
>Thanks, I'll look for that D, but is it increasing the accuracy?
>Will the accuracy reading on the GPS change?
>
>

Without SBAS correction (WASS/EGNOS) you typically don't see values on the
old eTrex's below 6m and reality that actually means 10m

With SBAS corrections the value on my old Legend drops to 2m at best,
although more often than not its 4m

When EGNOS was still operating as a test bed in Europe there were times when
accuracy would go down when WASS was enabled. From what I understand this
was due to issues relating to corrections being applied to satellites
emerging/leaving the field of, ie low on the horizon. The timing information
from sats close to the horizon can be influenced and thus correction values
could negatively impact the final result. Perhaps unit firmware updates
improved this, I don't know. Anyway, I haven't seen this as an issue
recently although I have to say generally that I rarely notice much
difference in the accuracy between WASS on or off when using the device on
the bike.

Cheers

Andy





More information about the newbies mailing list