I found this report on the etrex 20 (same as etrex 30 other than some
missing features (baro/compass)).

This screen shot:
http://gpstracklog.com/wp-content/up...Trex_thumb.jpg

Shows that it appears to be (at least) a 12-GPS-channels and 12-GLONASS
channel unit.

As shown it's got 12 GPS "in view" and 11 GLONASS "in view" while
tracking 9 GPS and 6 GLONASS sats (total 15). No WAAS sats in the GPS
line ... maybe tracked on another channel, not listed?

The "error" calc (9 ft) seems optimistic since the best contributors to
horizontal accuracy were not being tracked (esp. to the north) and there
is no sure indication of WAAS tracking at the time either.

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On Oct 27, 1:56*pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:
> I found this report on the etrex 20 (same as etrex 30 other than some
> missing features (baro/compass)).
>
> This screen shot:http://gpstracklog.com/wp-content/up...SS-on-eTrex_th...
>
> Shows that it appears to be (at least) a 12-GPS-channels and 12-GLONASS
> channel unit.

Appears to use the NMEA convention for numbering satellites:

a) GPS satellites are identified by their PRN numbers, which range
from 1 to 32.

b) The WAAS system has reserved numbers 33 – 64 to identify its
satellites.

c) The numbers 65 – 96 are reserved for GLONASS satellites. GLONASS
satellites are identified by 64+ satellite
slot numbers. The slot numbers are 1 through 24 for the full GLONASS
constellation of 24 satellites, thus giving a
range of 65 through 88. The numbers 89 through 96 are available if
slot numbers above 24 are allocated to on-orbit
spares.

--- CHAS

On 2011-10-27 17:09 , HIPAR wrote:
> On Oct 27, 1:56 pm, Alan Browne<alan.bro...@FreelunchVideotron.ca>
> wrote:
>> I found this report on the etrex 20 (same as etrex 30 other than some
>> missing features (baro/compass)).
>>
>> This screen shot:http://gpstracklog.com/wp-content/up...SS-on-eTrex_th...
>>
>> Shows that it appears to be (at least) a 12-GPS-channels and 12-GLONASS
>> channel unit.
>
> Appears to use the NMEA convention for numbering satellites:
>
> a) GPS satellites are identified by their PRN numbers, which range
> from 1 to 32.
>
> b) The WAAS system has reserved numbers 33 – 64 to identify its
> satellites.
>
> c) The numbers 65 – 96 are reserved for GLONASS satellites. GLONASS
> satellites are identified by 64+ satellite
> slot numbers. The slot numbers are 1 through 24 for the full GLONASS
> constellation of 24 satellites, thus giving a
> range of 65 through 88. The numbers 89 through 96 are available if
> slot numbers above 24 are allocated to on-orbit
> spares.
>

Sure - like I said - no WAAS on that display. But that doesn't mean WAAS
wasn't being tracked.


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gmail originated posts filtered due to spam.

Sure - like I said - no WAAS on that display. But that doesn't mean
WAAS wasn't being tracked.

On my Etrex Vista HCx, I dimly recall that the default was to disable
WAAS. Once enabled, I see "PRN" 48 or 51 and D in many of the
satellites. This receiver is obviously in default mode because the
first thing anyone would do is set it to metric :-)

One has to wonder how the combined GPS/GLONASS solution is done in the
presence of WAAS, in terms of the GPS+D vs GLONASS a priori error
estimates. This is arguably a similar situation to GPS vs GPS+D, but it
seems likely to have eg 8 GPS+D and 6 Glonass over long periods of time.


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On 2011-10-27 19:58 , Greg Troxel wrote:
>
> Sure - like I said - no WAAS on that display. But that doesn't mean
> WAAS wasn't being tracked.
>
> On my Etrex Vista HCx, I dimly recall that the default was to disable
> WAAS. Once enabled, I see "PRN" 48 or 51 and D in many of the
> satellites. This receiver is obviously in default mode because the
> first thing anyone would do is set it to metric :-)

Only in the real world. Americans have metric paralysis unless they
were in the military or have a general science education.

Note that the _primary_ system of weights and measures in the US _is_
the metric system since the 1890's. Unfortunately, due to a lot of
trade with Britain, the US put an exception clause in the law.

> One has to wonder how the combined GPS/GLONASS solution is done in the
> presence of WAAS, in terms of the GPS+D vs GLONASS a priori error
> estimates. This is arguably a similar situation to GPS vs GPS+D, but it
> seems likely to have eg 8 GPS+D and 6 Glonass over long periods of time.

You'd get mostly WAAS'd GPS + un-SBAS'd GLONASS in the solution. A
clever algorithm might, post acquisition, kick out the GLONASS from the
solution so that it doesn't pollute it.

IAC, I know several ground truth points that are easy to identify and
that register well on Google Earth - I'll be testing the etrex 30 at
those points when I get it.

Note that in Europe the EGNOS signal covers GLONASS as well as GPS, so
performance there could be even better than in N.A. (Speculative).

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On Oct 28, 1:43*pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:
> On 2011-10-27 19:58 , Greg Troxel wrote:
>
>
>
> > * *Sure - like I said - no WAAS on that display. But that doesn't mean
> > * *WAAS wasn't being tracked.
>
> > On my Etrex Vista HCx, I dimly recall that the default was to disable
> > WAAS. *Once enabled, I see "PRN" 48 or 51 and D in many of the
> > satellites. *This receiver is obviously in default mode because the
> > first thing anyone would do is set it to metric :-)
>
> Only in the real world. *Americans have metric paralysis unless they
> were in the military or have a general science education.
>
> Note that the _primary_ system of weights and measures in the US _is_
> the metric system since the 1890's. *Unfortunately, due to a lot of
> trade with Britain, the US put an exception clause in the law.
>
> > One has to wonder how the combined GPS/GLONASS solution is done in the
> > presence of WAAS, in terms of the GPS+D vs GLONASS a priori error
> > estimates. *This is arguably a similar situation to GPS vs GPS+D, butit
> > seems likely to have eg 8 GPS+D and 6 Glonass over long periods of time..
>
> You'd get mostly WAAS'd GPS + un-SBAS'd GLONASS in the solution. *A
> clever algorithm might, post acquisition, kick out the GLONASS from the
> solution so that it doesn't pollute it.
>
> IAC, I know several ground truth points that are easy to identify and
> that register well on Google Earth - I'll be testing the etrex 30 at
> those points when I get it.
>
> Note that in Europe the EGNOS signal covers GLONASS as well as GPS, so
> performance there could be even better than in N.A. *(Speculative).
>
> --
> gmail originated posts filtered due to spam.

The most important factor that SBAS brings to single frequency users
is IONO corrections, GPS CDMA L1 is centered on 1575 MHz while GLONASS
L1 is 1602 MHz + n X 0.5625 (where n is the FDMA channel), so with the
neighboring frequency characteristics, I don't see why GPS IONO
couldn't be used for GLONASS IONO corrections without adjustment (with
the accuracy gain of adding IONO corrections to GLONASS completely
making up for any tiny diference in aprox 30 MHz spacing between GPS
and GLONASS).

If your unit receives SBAS and applies the IONO grid for GLONASS
satellites as well, <3 meter accuracy @ 80% probability would be
totally doable.
I read in some SBAS papers studying triple frequency + multi
constellation SBAS that since GPS and Galileo use the same L1 and L5
frequencies, that IONO measurements are completely interchangeable
between them.

The same paper explains that if the SBAS reference stations use
multiple constellations even without broadcasting corrections for
those extra constellations the extra IONO measurements will improve
IONO accuracy and certainty substantially. For instance considering
WAAS with GPS+Galileo+EGNOS with users using current single frequency
+ single constellation receivers would benefit from a more precise
IONO grid. Also using L1+L5 for IONO calculations is substantially
better than semi codeless due to the larger frequency spacing and
capability to track L1 and L5 at lower angles than P(Y) signals in
semi codeless mode.

I wonder if someone with more precise understanding could confirm /
correct me.

On 2011-10-28 13:05 , macpacheco wrote:
> On Oct 28, 1:43 pm, Alan Browne<alan.bro...@FreelunchVideotron.ca>
> wrote:
>> On 2011-10-27 19:58 , Greg Troxel wrote:
>>
>>
>>
>>> Sure - like I said - no WAAS on that display. But that doesn't mean
>>> WAAS wasn't being tracked.
>>
>>> On my Etrex Vista HCx, I dimly recall that the default was to disable
>>> WAAS. Once enabled, I see "PRN" 48 or 51 and D in many of the
>>> satellites. This receiver is obviously in default mode because the
>>> first thing anyone would do is set it to metric :-)
>>
>> Only in the real world. Americans have metric paralysis unless they
>> were in the military or have a general science education.
>>
>> Note that the _primary_ system of weights and measures in the US _is_
>> the metric system since the 1890's. Unfortunately, due to a lot of
>> trade with Britain, the US put an exception clause in the law.
>>
>>> One has to wonder how the combined GPS/GLONASS solution is done in the
>>> presence of WAAS, in terms of the GPS+D vs GLONASS a priori error
>>> estimates. This is arguably a similar situation to GPS vs GPS+D, but it
>>> seems likely to have eg 8 GPS+D and 6 Glonass over long periods of time.
>>
>> You'd get mostly WAAS'd GPS + un-SBAS'd GLONASS in the solution. A
>> clever algorithm might, post acquisition, kick out the GLONASS from the
>> solution so that it doesn't pollute it.
>>
>> IAC, I know several ground truth points that are easy to identify and
>> that register well on Google Earth - I'll be testing the etrex 30 at
>> those points when I get it.
>>
>> Note that in Europe the EGNOS signal covers GLONASS as well as GPS, so
>> performance there could be even better than in N.A. (Speculative).
>>
>> --
>> gmail originated posts filtered due to spam.
>
> The most important factor that SBAS brings to single frequency users

I don't care about the principles of WAAS. I know plenty enough.

I care about the implementation in this particular device.

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