HOME
- StartseiteQuestions & Answers
|
Date |
Question |
Raytheon's Response |
| 06/21/2002 | I am in Yakima Washington and have a challenge getting WAAS when I go into the foothills of the Cascade Mountains. Can you comment on "Soon a Pacific satellite will also broadcast the WAAS correction, enabling the Pacific Northwest and Alaska to have full WAAS coverage."? | I'm not sure how
old that statement is ... there has been a transmitting GEO over the Pacific
for several years now. Clearly, all GEOs are relatively low on the horizon,
so it is certainly possible to get signal shielding on the north side of
mountains and in canyons. The FAA is in the process of procuring a 3rd GEO, which may alleviate some of your signal problems. The location of this new GEO has still not been determined, but where ever it is, it will provide additional signals from a different azimuth ... reducing (but not necessarily eliminating) any shielding situations. |
| 04/11/2002 | I recently bought a hand held computer with a NAVMAN GPS receiver and periodically the WAAS indicator will come on. From what I read the signal comes from Brazil and I need to have a clear line of site to the horizon towards Brazil in order to pick up the signal. Why is it so hard to pick up the signal and why does it eat the battery so quick when it does pick it up? And will the signal always come from the same location....South East. | The WAAS signals
are broadcast from 2 Geo Stationary satellites (AOR-W and POR). The WAAS
signal, like GPS signals, are line of site, and so an unobstructed view of
the GEO satellite is needed to receive the WAAS signals. The direction to
the GEOs is obviously dependent upon your location. The AOR-W satellite is
located above Brazil. As to battery consumption, you will need to contact the manufacturer of the GPS receiver. We are not aware of any reason why the battery life should be shortened by the reception of the WAAS signal. |
|
09/19/2001 |
I'm curious what could happen during the upcoming events around the world as far as WAAS availability for agricultural purposes. Can/Will the WAAS signal be shut off during US military events for Ag use? | WAAS includes a
capability called "Military Emergency Mode". In this mode, the WAAS signal
is broadcast, but there are no fast corrections. This mode is invoked at the
prerogative of the US Air Force. There have been no discussions that I am
aware of to date regarding using this mode in the near future. In general,
Raytheon views this as an unlikely possibility.
If we are requested to change to Military Emergency Mode, we will update the WAAS Web page with an indication that the signal is intentionally being degraded. If we can, we will also post to the web page when we expect the system to be returned to Normal mode. |
|
08/25/2001 |
How did the WAAS system respond to the PRN22 incident on 28 July 2001? Did the system flag PRN22 as unhealthy before it was SatZap'ed? | WAAS immediately detected and corrected for the problems PRN 22 was experiencing on July 28th. WAAS supplied appropriate corrections until the correction value no longer fit into the message format. At that point, WAAS set PRN 22 to "Do Not Use." |
|
08/23/2001 |
I receive AOR-W signal very strong here in Caracas, Venezuela and the other GPS satellites with the "D" symbol indication of correction (including the AOR-W). Why the accuracy does not change dramatically? Normaly with the WAAS disabled the accuracy is around 6 to 7 meter, and with WAAS enabled the accuracy is around 7 meters without any significant change. I am thinking my Garmin unit is not working properly or the WAAS system does not have IONO correction of South America specifically Venezuela and surroundings. Please keep me in touch regarding this situation, I don't want trying to work the unit with the WAAS enabled if the system is not yet designed to be used outside the US. | Thanks for the
e-mail. It's great to hear from WAAS user's outside of the United States.
Most likely your Garmin is working just fine. WAAS does not broadcast iono
correction information for South America. This will limit the accuracy a
WAAS capable receiver, but will not degrade it, and in-fact should give you
greater confidence in the accuracy estimation that the unit is providing you.
We have seen situations were a GPS satellite goes "haywire", WAAS immediately flagged it as bad and notified WAAS users. If the Garmin recognizes these messages, the bad satellite would be dropped from the solution set and a better accuracy would be achieved. Raytheon is hoping that in the near future, WAAS will be expanded to cover all of North and South America or a separate WAAS-like system will be in place for South America. |
|
07/11/2001 |
Why can't I receive WAAS on my handheld GPS receiver, from the n=map it "appears" I should be able to receive POR and AOR-W? | Many of the handhelds on the market today do not include the capability to receive or process the WAAS messages. Are you sure your unit is WAAS capable? |
|
07/11/2001 |
When will more geostationary satellites be available to provide better WAAS coverage for northern California? | The FAA is preparing a request for additional WAAS GEO satellites. It takes roughly three years to define, build, orbit, and commission a new satellite, so the earliest a new satellite is expected is 2004. |
|
06/22/2001 |
What is the current coverage of the two satellites? Is there a map somewhere? | The link below will
get you to the Inmarsat coverage maps. WAAS is using the AOR-W and POR
satellites. http://217.204.152.210/support_maps.cfm The maps show where the theoretical coverage areas where the WAAS signal could be received. Towards the edges, the satellite is viewed low on the horizon and the possibility of signal blockage increases. |
|
12/15/2000 |
Is there a way that your system can be used with a Garmin Chart plotter? I heard that an antenna can be added to get the signal. | In general, any GPS
antenna will work with the WAAS signal; it is the same type of signal the
GPS satellites broadcast. The receiver must have the capability to decode
the WAAS message and apply the corrections. We do not have information from
receiver manufactures as to when they plan to add a WAAS capability. I would
recommend you contact Garmin directly regarding their products.
The Raychart 320 is a Raytheon Marine product that provides a WAAS capable GPS chartplotter. Raychart web site: http://www.raymarine.com/recreational/products/index/navaids/index.html |
|
09/26/2000 |
I have just purchased a Raynav 300 GPS Plotter. Does the transmission of the "O" test signal mean that I will not be able to use my plotter in the WAAS mode? | Even though the
WAAS system is still in the testing phase for the FAA the signal can be used
for non-aviation applications. The RN300 will display an SD (Satellite
Differential) indication when it is receiving the WAAS signal. The SD will
disappear if WAAS is not being received. Currently the WAAS signal is being transmitted almost continuously. |
|
09/07/2000 |
Request from the
European Space Agency to update our EGNOS information.
|
Please note that
today EGNOS is transmitting through what we call the EGNOS System Test Bed
(ESTB) which is similar to the US NSTB. This ESTB is only for testing and it
is currently using AOR-E (in the near future, there will also be
broadcasting through the Inmarsat IOR). Please note the EGNOS website
address and the ESTB schedule address: EGNOS website: http://www.esa.int/navigation/ESTB schedule website: http://www.esa.int/navigation/pages/indexEST.htm
|
|
09/07/2000 |
I own a Beech Bonanza with a Garmin 530 GPS installed. I would like to know what the WAAS system will do for me and will it be automatically in use on my GPS. | When the FAA
certifies WAAS for IFR operation, a couple of changes will be possible in
your flight planning and operation. First, RAIM checks will no longer be
required, since GPS/WAAS availability will far exceed GPS/RAIM availability
(which is already very good). Second, and perhaps most importantly, you will
be able to conduct approaches with vertical guidance even to runways that
are not equipped with an ILS. The FAA is currently charting these
three-dimensional approaches in anticipation of WAAS commissioning, and
intends over time to replace virtually all existing non-precision approaches
with WAAS-based precision approaches. By the time they are done, 4000
airports will be charted for these vertical-guidance approaches, with almost
all thresholds at each airport having their own 3-D approach----no more need
to conduct "fly-and-dive" step-down or circling approaches.
Current plans call for a phased delivery of WAAS, both from a system capability perspective and approach publication. At commissioning, we expect WAAS to support approaches with vertical guidance down to minimums ranging from as low as 250 feet (optimum terrain) to approximately 350 feet and about 1 mile visibility (unusual obstacles could require higher minimums.) This capability will exist with at least 95 percent availability over about 50 percent of the lower 48 states. Subsequent phases of the program will 1.) expand approach capability throughout the lower 48 states, much of Alaska, southern Canada, and Mexico, and 2.) progressively lower the approach minimums that the system will support until a WAAS approach is essentially the same as a Category I ILS approach. Concurrent with this system enhancement and coverage expansion, the FAA will add system redundancy (especially additional geostationary satellites) so that WAAS will be declared the sole means of navigation required for installation in the airplane. The FAA plans to maintain a minimum number of existing navigation aids for the indefinite future, but as the decade progresses, navigation in the national airspace system will become increasingly dependent upon WAAS. The WAAS upgrade path for different receivers will likely vary by model and manufacturer. We suggest you contact directly the manufacturer of your receiver for information on what will be required to activate or upgrade the receiver to WAAS capability. |
| 8/21/00 | Raytheon does not
transmit message #12 (WAAS-UTC time difference). Why? Is it possible to use
a GEO satellite like an additional GPS satellite (using only the GEO
navigation message #9 for satellite position and time delay computation)? Assuming that WAAStime == GPStime we have range residual for GEO satellite sometimes approaching 10 meters. Does this seem right? |
Raytheon does not
broadcast the type 12 message because the data for that message is not yet
provided to WAAS by the USNO.
The type 12 message is not needed to use a GEO as a GPS ranging source. The GEO ranging data and the WAAS type 9 message provide sufficient information. The assumption is made that WAAS Network Time is equivalent to GPS time. (WAAS has a requirement to maintain WAAS Network Time to within 50 ns of GPS time. A range residual of 10 meters for a GEO does occur (more often for POR than for AOR-W). |
|
08/16/2000 |
I was thinking of
purchasing the Raychart 420 or the Raychart 320. It sounds as though the 320
will be more accurate than the 420. At the WAAS website it states the
corrections made by WAAS will be sent to GPS receivers - I get the
impression all GPS will be sent more accurate info.
I would like to know if the new WAAS signal will be picked up by regular GPS receivers (not differential recievers). Will the 420 be able to receive the WAAS corrections? |
While the WAAS
messages are broadcast in a manner consistent with GPS messages, the content
of a WAAS message is different. The WAAS messages contain correction and
integrity information. The receiver must be designed to accept and process
the WAAS messages in addition to the regular GPS messages.
The Raychart 420 is not a WAAS capable receiver. The Raychart 320 is a new product and includes a WAAS capable receiver. The 320 will be more accurate. |
|
06/12/2000 |
Where can I obtain information about the certification of WAAS? | Certification information about WAAS can be obtained from the FAA WAAS program office. For more information, please refer to the FAA WAAS web page at http://gps.faa.gov/Programs/WAAS/waas.htm. |
|
06/12/2000 |
When will WAAS be transmitting a Type 2 message? | It is not expected that WAAS will transmit a Type 2 message until WAAS is certified. The current Type 0 message contains the same data in the data fields as the Type 2 except that the message header is labeled as a Type 0. |
|
05/30/2000 |
What is the difference between AOR-W (PRN 122) and POR (PRN 134)? | The signal over the Atlantic Ocean Region - West (AOR-W) is identified with a Pseudo Random Noise (PRN) of 122. The Pacific Ocean Region (POR) uses PRN 134. |
|
01/14/2000 |
...I would like to know if the MESSAGE 17 of WAAS message is currently broadcasted and usable to compute satellite visibility? | We are not aware of any previously discontinued broadcast of Type 17 Message to WAAS SIS, and as far as we know, it is currently being broadcast. |
|
12/22/1999 |
...we are seeing the receiver periodically do a "locktime reset".....and ocassional go into a "reacq" mode.... My question to you is are you seeing similar results with your receivers and is this behavior due to some problem at the ground station? | Please refer your questions to the FAA Tech Center. They should be able to have answers for you. |
|
12/20/1999 |
I visited your WAAS broadcast schedule site and found it very useful. Do you know of a similar site for EGNOS? In particular, I am interested in scheduling information for AOR-E. Thank you. | I am not sure if a
web page containing AOR-E schedule exists. Sorry. See 09/07/00 for updates. |
|
12/15/1999 |
I inspected the WAAS Broadcast Web Site and found that on Oct 9,17, and 28 Type 2 messages had been broadcast. Could you please advise as to when the next Type 2 message broadcasts will occur. | Although a planned Type 2 Message is not an outage of signal, it will still be listed under the Planned Broadcast Outage Schedule Table. The web site also contains a 7 days historical data of SIS and is updated daily (except for holidays) to reflect the most current data. |