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Author Topic: BU-353 - WAAS Enabled?  (Read 3997 times)

GS_TECH01

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BU-353 - WAAS Enabled?
« on: February 24, 2011, 07:42:13 pm »

By default, the BU-353 is WAAS Enabled if you bought it directly from us or from one of our authorized resellers.

Another way to determine that your unit is WAAS Enabled is by using the GPSInfo program (http://www.usglobalsat.com/store/download/62/vista_32bit_gps_info_utility.zip).
Plug-in the device to your computer. Open up the said program, select the correct com port, and leave the baud rate to 4800. Click Start GPS. After a few seconds, press the Cold Start button. The box besides the WAAS/EGNOS will be automatically checked.

After the Cold Start button is pressed, you can also check the messages coming out from the device which is something like this:

$PSRFTXT,Version:GSW3.5.0_3.5.00.00-SDK-3EP2.01 *46
$PSRFTXT,Version2:F-GPS-03-0904011*20
$PSRFTXT,WAAS Enable*66
$PSRFTXT,TOW:  0*25
$PSRFTXT,WK:   1519*69
$PSRFTXT,POS:  6378137 0 0*2A
$PSRFTXT,CLK:  96250*25
$PSRFTXT,CHNL: 12*73
$PSRFTXT,Baud rate: 4800*65
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mmaarrkk

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Re: BU-353 - WAAS Enabled?
« Reply #1 on: May 31, 2011, 03:09:53 pm »

I recently purchased four BU-353s from an authorized reseller and I have confirmed that the $PSRFTXT,WAAS Enable*66 message is displayed following a cold start using the gps_info utility.  However, I don't see any indication in the "fix quality" field in the GGA message.  On other GPS units I see this field change from 1 to 2.
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GS_TECH01

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Re: BU-353 - WAAS Enabled?
« Reply #2 on: May 31, 2011, 11:09:17 pm »

Regarding the 'fix quality' in the GGA message, do you mean the Position Fix Indicator? For more info, please refer to this NMEA document (pg. 1-2 - 1-3): http://www.usglobalsat.com/store/downloads/NMEA_commands.pdf
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mmaarrkk

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Re: BU-353 - WAAS Enabled?
« Reply #3 on: June 01, 2011, 11:44:06 am »

Yes, the Position Fix Indicator.  Shouldn't it be set to 2 when the position solution is differentially corrected using WAAS.  I am testing in multiple locations with a good view of the sky and I never see the Position Fix Indicator change from 1 to 2.   
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GS_TECH01

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Re: BU-353 - WAAS Enabled?
« Reply #4 on: June 03, 2011, 07:07:40 pm »

Can you please check the firmware version of your device? In order to do that, please refer here: http://www.usglobalsat.com/forum/index.php?topic=3514.msg8979#msg8979
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DSUStechnical

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Re: BU-353 - WAAS Enabled?
« Reply #5 on: June 09, 2011, 12:06:19 pm »

Having just bought several GlobalSat BU-353 units with the expectation for the capability of the devices to compute an SBAS corrected 'differential' (DGPS) 3D position fix, it has been found that at no time do any of the units do so...

Each BU-353 unit only computes a 'standalone' 3D position fix despite using the 'factory default' settings etc...

      $PSRFTXT,Version:GSW3.5.0_3.5.00.00-SDK-3EP2.01 *46
      $PSRFTXT,Version2:F-GPS-03-1006231*2A
      $PSRFTXT,WAAS Enable*66
      $PSRFTXT,TOW:  0*25
      $PSRFTXT,WK:   1519*69
      $PSRFTXT,POS:  6378137 0 0*2A
      $PSRFTXT,CLK:  96250*25
      $PSRFTXT,CHNL: 12*73
      $PSRFTXT,Baud rate: 4800*65 


Sample NMEA data is:-

$GPGGA,203901.000,2950.5123,N,09533.9439,W,1,11,0.9,32.5,M,-23.7,M,,0000*51
$GPGSA,A,3,23,20,07,16,03,06,32,19,13,10,08,,1.6,0.9,1.3*3A
$GPGSV,3,1,12,23,74,157,37,13,67,321,37,03,52,086,36,19,44,136,35*7F
$GPGSV,3,2,12,06,40,069,33,16,33,038,34,07,29,305,32,10,16,298,29*78
$GPGSV,3,3,12,20,15,202,26,08,08,288,25,32,06,180,18,11,02,168,*77
$GPRMC,203901.000,A,2950.5123,N,09533.9439,W,0.07,42.56,080611,,,A*49
etc...

The results seen are that the while the units are computing a 3D fix:-
    o NMEA GGA telegram message Mode Indicator field always equals ‘1’
    o NMEA GGA telegram message differential correction age field always ‘null’
    o NMEA GGA telegram message Reference Station ID field always equal to ‘0000’
    o NMEA RMC telegram message Mode Indicator field always equals ‘A’
    o NMEA GSV telegram messages never show tracking of any SBAS PRN IDs

So delving deeper into the BU-353 SiRFIII operation by using the 'SirfDemo' application, it was found that the SBAS PRN ID for North Americas (WAAS) was being tracked (Channel #12), however the device was not using the WAAS PRN for any differential correction 3D position fix solution, or reporting the WAAS PRN ID in the NMEA GSA or GSV telegram messages...  The question is; WHY?

It appears that the GlobSat BU-353 device requires "a strong" SBAS PRN satellite tracking signal in order to compute a differential GPS 3D position fix as advertised (ie; WAAS enabled default unit)...  Placement of the unit outside with a clear view of the sky is required.  Placing near a window may not work very well to obtain a DGPS 3D fix solution.


« Last Edit: June 10, 2011, 01:03:01 pm by DSUStechnical »
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GS_TECH01

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Re: BU-353 - WAAS Enabled?
« Reply #6 on: June 28, 2011, 01:33:00 pm »

Hi DSUStechnical,

Per your email discussions with Jesse, the BU-353 does support WAAS/EGNOS. For the optimal location, just place the unit outside with a clear access to an open sky and observe the data.

Feel free to ask us if you have any questions. Thanks.
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