[STL Geocaching] Re: New cache, needs boat
- From: "Dan Eubanks" <deubanks@xxxxxxxxxxxxxxxx>
- To: <geocaching@xxxxxxxxxxxxx>
- Date: Wed, 10 Apr 2002 10:23:25 -0500
This warning was issued today from Raytheon for those using WAAS in flight
navigation:
Safety Issue
WARNING: The Wide Area Augmentation System is currently under development
and test prior to FAA certification for safety-of-flight applications.
Raytheon is currently broadcasting a Type 0 (test mode) message to preclude
use of the signal for Instrument Flight Rule operations. During this period
Raytheon cannot guarantee the accuracy, integrity, continuity, or
availability of the WAAS signal. Raytheon accepts no responsibility for the
use of the signal for other than the above stated purpose. It is the user's
responsibility to exercise common prudence and navigational judgment while
using the WAAS signal.
Users are reminded that the WAAS has not been commissioned for use in safety
of life applications.
Today a Type "2" augmentation message is not being broadcast so all you
Geocachers who are WAAS ready keep in mind that you will not get the
accuracy you are accustom to. For more details go to
http://wwws.raytheontands.com/waas/.
Dan
-----Original Message-----
From: geocaching-bounce@xxxxxxxxxxxxx
[mailto:geocaching-bounce@xxxxxxxxxxxxx]On Behalf Of Paul Becker
Sent: Tuesday, April 09, 2002 3:27 PM
To: geocaching@xxxxxxxxxxxxx
Subject: [STL Geocaching] Re: New cache, needs boat
>>From: Dan Eubanks
>>WAAS stands for Wide Area Augmentation System. This is a series of ground
based antenna signals that
>>are placed in North America. They are similar to GPS signals. If your GPS
Unit is set up to receive
>>WAAS signals then your accuracy goes from about 20' to 2' on a good day.
This system is still under
>>development and promised to get better as time goes by. Soon all GPS units
will be WAAS capable as
>>a standard feature.
Minor nit-pick...
WAAS uses 25 ground-based reference stations for error measurement data
collection ONLY. These stations do not transmit the actual WAAS signal as
received by the GPS receivers. They measure pseudorange errors for each
satellite as well as other sources of timing error (such as ionospheric and
tropospheric signal propogation delays). The measurements are sent to a
master control station, where they are processed and transmitted up to a set
of geostationary satellites which broadcast the actual WAAS signals to all
listening WAAS-capable receivers.
For it to be most effective, though, the GPS must be within a region
serviced by at least one of the monitoring stations. Why? Because
ionopheric delays are constantly changing and relatively local in nature.
It is possible to have MORE error using WAAS than without it.
This is unlike the DGPS (RTCM) network operated by the Coast Guard, which
require a DPGS receiver and a DGPS-capable GPS. In addition, you must be
within range of a DGPS transmitting station (there's one in St. Louis). In
the case of DGPS, the ground station both measures the errors AND transmits
the signals.
I told you I was just nit-picking, but I thought someone might be
interested. For more information:
http://wwws.raytheontands.com/waas/
http://waas.stanford.edu/tmslive/
Yes, I do wear a propeller cap.
Paul
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