[gps-talkusers] Re: What is WAAS?

  • From: "Claude Everett" <claudeeverett@xxxxxxxxxxx>
  • To: <gps-talkusers@xxxxxxxxxxxxx>
  • Date: Fri, 23 Sep 2005 20:46:23 -0700

Hi, Michael
,
Thanks for the clarification.
----- Original Message ----- From: "Michael May" <mikemay@xxxxxxxxxxxxxxxx>
To: <gps-talkusers@xxxxxxxxxxxxx>
Sent: Friday, September 23, 2005 7:52 PM
Subject: [gps-talkusers] Re: What is WAAS?



The specs for any GPS receivers will indicate if it has
WAAS or not. These days, most will.

As I indicated in two other emails, the Blue Logger has WAAS. The GlobalSat used on the Pac Mate and other Sirf 3 GPS receivers do not have WAAS turned on by default. You have to enable WAAS with their PC software.

Mike


At 06:41 PM 9/23/2005, you wrote:
Hi, Richard,
That all sounds real great, and I appreciate all of the information. But, the question that is probably burning in the mind of everyone on this list including myself, is:
what GPS receivers are "WAAS", enabled, and how can I tell if my GPS has the "WAAS" enabled?
Using the "Blue Logger",
Claude
----- Original Message ----- From: "Richard Myers" <dkmyers28@xxxxxxxxxxx>
To: <gps-talkusers@xxxxxxxxxxxxx>
Sent: Friday, September 23, 2005 2:57 PM
Subject: [gps-talkusers] What is WAAS?



What is WAAS?


You've heard the term WAAS, seen it on packaging and ads for Garmin®
products, and maybe even know it stands for Wide Area Augmentation
System. Okay, so what the heck is it? Basically, it's a system of
satellites and ground stations that provide GPS signal corrections,
giving you even better position accuracy. How much better? Try an
average of up to five times better. A WAAS-capable receiver can give
you a position accuracy of better than three meters 95 percent of
the time. And you don't have to purchase additional receiving
equipment or pay service fees to utilize WAAS.
The origins of WAAS
The Federal Aviation Administration (FAA) and the Department of
Transportation (DOT) are developing the WAAS program for use in
precision flight approaches. Currently, GPS alone does not meet the
FAA's navigation requirements for accuracy, integrity, and
availability. WAAS corrects for GPS signal errors caused by
ionospheric disturbances, timing, and satellite orbit errors, and it
provides vital integrity information regarding the health of each
GPS satellite.
How it Works
WAAS consists of approximately 25 ground reference stations
positioned across the United States that monitor GPS satellite data.
Two master stations, located on either coast, collect data from the
reference stations and create a GPS correction message. This
correction accounts for GPS satellite orbit and clock drift plus
signal delays caused by the atmosphere and ionosphere. The corrected
differential message is then broadcast through one of two
geostationary satellites, or satellites with a fixed position over
the equator. The information is compatible with the basic GPS signal
structure, which means any WAAS-enabled GPS receiver can read the
signal.
Who benefits from WAAS?
Currently, WAAS satellite coverage is only available in North
America. There are no ground reference stations in South America, so
even though GPS users there can receive WAAS, the signal has not
been corrected and thus would not improve the accuracy of their
unit. For some users in the U.S., the position of the satellites
over the equator makes it difficult to receive the signals when
trees or mountains obstruct the view of the horizon. WAAS signal
reception is ideal for open land and marine applications. WAAS
provides extended coverage both inland and offshore compared to the
land-based DGPS (differential GPS) system. Another benefit of WAAS
is that it does not require additional receiving equipment, while
DGPS does.
Other governments are developing similar satellite-based
differential systems. In Asia, it's the Japanese Multi-Functional
Satellite Augmentation System (MSAS), while Europe has the Euro
Geostationary Navigation Overlay Service (EGNOS). Eventually, GPS
users around the world will have access to precise position data
using these and other compatible systems.
It just keeps getting better
100 meters:Accuracy of the original GPS system, which was subject to
accuracy degradation under the government-imposed Selective
Availability (SA) program.
15 meters:Typical GPS position accuracy without SA.
3-5 meters:Typical differential GPS (DGPS) position accuracy.
< 3 meters:Typical WAAS position accuracy.




(8):[(8)





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Michael G. May

CEO Sendero Group

Developers and distributors of BrailleNote GPS
Distributing BrailleNote, VoiceNote, Miniguide, The Tissot Silen-T tactile watch, and the ID Mate bar code reader


MikeMay@xxxxxxxxxxxxxxxx
http://www.SenderoGroup.com

(1-888-757-6810, Fax (530) 757-6830, Mobile (530) 304-0007
Sendero Group, LLC
1118 Maple Lane, Davis, CA 95616-1723, USA

Latitude, 38 33 9.239 North
Longitude, 121 45 40.145 West




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