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- Single-Point-GPS-for-Heading-Determination
- 05-08-2009
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Traditionally we use two receivers capable of RTK to determine the
heading. However, I heard recently that some researchers were capable
of using two receivers at single point positioning (with carrier phase
smoothing) to determine the heading. With about 1 meter baseline, they
were capable of achieving heading accuracy at 0.1 degree rms. Is it
possible? How can they remove the common errors?
I guess they will synchronize the receiver, so the receiver clock
errors will be removed. Then they might feed both the raw measurements
of both receivers to a central CPU to do the RTK. However, RTK will
still be involved in this case. Is it possible to go without RTK?
codeguru4job@gmail.com wrote:
All RCCL cruise ships use this system to determine heading, you use the
raw signals from each GPS to determine the phase difference for each
visible sat.
With a baseline of just 1m and 1.5 GHz L1 frequency (20 cm wave length),
the maximum difference (for a sat near the horizon, directly ahead or
behind the ship) will be about 5 periods, right?
With all other sats at less than 5 periods away, it seems very feasible
to measure the fractional offset for each sat, and then simply try all
possible directions to find the one that minimizes the error (offset
between measured and calculated from Sat and ship positions).
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
Terje Mathisen wrote:
> codeguru4job@gmail.com wrote:
>> Traditionally we use two receivers capable of RTK to determine the
>> heading. However, I heard recently that some researchers were capable
>> of using two receivers at single point positioning (with carrier phase
>> smoothing) to determine the heading. With about 1 meter baseline, they
>> were capable of achieving heading accuracy at 0.1 degree rms. Is it
>> possible? How can they remove the common errors?
>> I guess they will synchronize the receiver, so the receiver clock
>> errors will be removed. Then they might feed both the raw measurements
>> of both receivers to a central CPU to do the RTK. However, RTK will
>> still be involved in this case. Is it possible to go without RTK?
>> heading. However, I heard recently that some researchers were capable
>> of using two receivers at single point positioning (with carrier phase
>> smoothing) to determine the heading. With about 1 meter baseline, they
>> were capable of achieving heading accuracy at 0.1 degree rms. Is it
>> possible? How can they remove the common errors?
>> I guess they will synchronize the receiver, so the receiver clock
>> errors will be removed. Then they might feed both the raw measurements
>> of both receivers to a central CPU to do the RTK. However, RTK will
>> still be involved in this case. Is it possible to go without RTK?
>
> All RCCL cruise ships use this system to determine heading, you use the
> raw signals from each GPS to determine the phase difference for each
> visible sat.
>
> With a baseline of just 1m and 1.5 GHz L1 frequency (20 cm wave length),
> the maximum difference (for a sat near the horizon, directly ahead or
> behind the ship) will be about 5 periods, right?
>
> With all other sats at less than 5 periods away, it seems very feasible
> to measure the fractional offset for each sat, and then simply try all
> possible directions to find the one that minimizes the error (offset
> between measured and calculated from Sat and ship positions).
>
> Terje
>
Thank you for your reply, Terje,
> All RCCL cruise ships use this system to determine heading, you use the
> raw signals from each GPS to determine the phase difference for each
> visible sat.
>
> With a baseline of just 1m and 1.5 GHz L1 frequency (20 cm wave length),
> the maximum difference (for a sat near the horizon, directly ahead or
> behind the ship) will be about 5 periods, right?
>
> With all other sats at less than 5 periods away, it seems very feasible
> to measure the fractional offset for each sat, and then simply try all
> possible directions to find the one that minimizes the error (offset
> between measured and calculated from Sat and ship positions).
>
> Terje
>
Could you please let me know why 5 periods? Give me a few more details.
Johnson
Johnson wrote:
> Terje Mathisen wrote:
>> With a baseline of just 1m and 1.5 GHz L1 frequency (20 cm wave
>> length), the maximum difference (for a sat near the horizon, directly
>> ahead or behind the ship) will be about 5 periods, right?
>> length), the maximum difference (for a sat near the horizon, directly
>> ahead or behind the ship) will be about 5 periods, right?
> Thank you for your reply, Terje,
>
> Could you please let me know why 5 periods? Give me a few more details.
>
> Could you please let me know why 5 periods? Give me a few more details.
Did you read anything I wrote above?
1m = 100cm
100 cm / 20 cm = 5
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
Terje Mathisen wrote:
> Johnson wrote:
>> Terje Mathisen wrote:
>>> With a baseline of just 1m and 1.5 GHz L1 frequency (20 cm wave
>>> length), the maximum difference (for a sat near the horizon, directly
>>> ahead or behind the ship) will be about 5 periods, right?
>>> length), the maximum difference (for a sat near the horizon, directly
>>> ahead or behind the ship) will be about 5 periods, right?
>> Thank you for your reply, Terje,
>> Could you please let me know why 5 periods? Give me a few more details.
>> Could you please let me know why 5 periods? Give me a few more details.
>
> Did you read anything I wrote above?
>
> 1m = 100cm
>
> 100 cm / 20 cm = 5
>
> Terje
>
Now I understand how 5 periods came out. Sorry I use wavelengths much
> Did you read anything I wrote above?
>
> 1m = 100cm
>
> 100 cm / 20 cm = 5
>
> Terje
>
more often than periods, so I didn't catch your meaning quickly.
"With all other sats at less than 5 periods away, it seems very feasible
to measure the fractional offset for each sat, and then simply try all
possible directions to find the one that minimizes the error (offset
between measured and calculated from Sat and ship positions".
It seems that you have confined the delta integer ambiguities of two
antenna to +-5 wavelengths, which seems reasonable, and then you tried
all possibilities to fix the delta integers, right? That is equivalent
to do RTK in a small region (+-5), right? I guess you still use LS
solutions, right?
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> heading. However, I heard recently that some researchers were capable
> of using two receivers at single point positioning (with carrier phase
> smoothing) to determine the heading. With about 1 meter baseline, they
> were capable of achieving heading accuracy at 0.1 degree rms. Is it
> possible? How can they remove the common errors?
> I guess they will synchronize the receiver, so the receiver clock
> errors will be removed. Then they might feed both the raw measurements
> of both receivers to a central CPU to do the RTK. However, RTK will
> still be involved in this case. Is it possible to go without RTK?