question about Thunderbolt geo acuracy
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and
one of those conical white aerials from china and would like to know if
this combination will give me accurate height data.
Thanks
Tim
How accurate do you need your height?
Remember that height is the least accurate of GPS parameters due to the fact
that you rarely have a GPS satellite directly overhead.
Rob Kimberley
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of swingbyte
Sent: 10 May 2012 13:50
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] question about Thunderbolt geo acuracy
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and one of
those conical white aerials from china and would like to know if this
combination will give me accurate height data.
Thanks
Tim
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and follow the instructions there.
On 05/10/2012 02:50 PM, swingbyte wrote:
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and one
of those conical white aerials from china and would like to know if this
combination will give me accurate height data.
There are many sides to this issue. You will most definitely be best
served by a choke-ring or similar antenna that suppresses multi-path
reflections. In addition to that, you would want Lady Heather to do a 24
hour position averaging. This should give you an OK solution, but really
not the best achievable.
Accurate height data is complex, since besides the receiver and antenna
issues, height data has more uncertainty than longitude and latitude
measures, and also since even if precise WGS84 height is achieved, you
would need to correct it to your datum, your sea-level etc.
You would also like to have better ionspheric correction than a plain
GPS solution gives you, but the Thunderbolt does not give you direct
support for such corrections.
Exactly how much effort you need to do depends on how accurate you need
it, +/- 10 m, 1 m, 1 dm, 1 cm or 1 mm.
Cheers,
Magnus
Not being able to receive signals from GPS satellites anywhere below
the horizon is an even larger problem for vertical accuracy.
On Thu, 10 May 2012 13:59:51 +0100, "Rob Kimberley"
robkimberley@btinternet.com wrote:
How accurate do you need your height?
Remember that height is the least accurate of GPS parameters due to the fact
that you rarely have a GPS satellite directly overhead.
Rob Kimberley
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of swingbyte
Sent: 10 May 2012 13:50
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] question about Thunderbolt geo acuracy
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and one of
those conical white aerials from china and would like to know if this
combination will give me accurate height data.
Tim
On Thu, 10 May 2012 22:50:15 +1000
swingbyte swingbyte@exemail.com.au wrote:
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and
one of those conical white aerials from china and would like to know if
this combination will give me accurate height data.
How fast do you need it?
One project i'm involved with uses a LEA6-T with its phase data output
and averaging over several hours to get x/y resolutions in the 2-4mm range.
I'm quite sure you can do something similar with altitude as well.
Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
On 5/10/12 6:08 AM, Magnus Danielson wrote:
On 05/10/2012 02:50 PM, swingbyte wrote:
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and one
of those conical white aerials from china and would like to know if this
combination will give me accurate height data.
There are many sides to this issue. You will most definitely be best
served by a choke-ring or similar antenna that suppresses multi-path
reflections. In addition to that, you would want Lady Heather to do a 24
hour position averaging. This should give you an OK solution, but really
not the best achievable.
Accurate height data is complex, since besides the receiver and antenna
issues, height data has more uncertainty than longitude and latitude
measures, and also since even if precise WGS84 height is achieved, you
would need to correct it to your datum, your sea-level etc.
You would also like to have better ionspheric correction than a plain
GPS solution gives you, but the Thunderbolt does not give you direct
support for such corrections.
Exactly how much effort you need to do depends on how accurate you need
it, +/- 10 m, 1 m, 1 dm, 1 cm or 1 mm.
If you can get RINEX format files, you can post process them through
GIPSY at JPL and get higher precision, using post determined ionospheric
and other corrections.
My friends in the GPS world say that getting to 1 meter absolute
position is fairly straightforward but once you start getting finer than
that, all the various factors start ganging up on you: ionosphere, solid
earth tides, multipath, phase center shifts, etc.etc.
Likewise, getting 1mm + 1 ppm of separation distance sorts of
uncertainty in a differential measurement is fairly straightforward.
A man with only one GPS ........
Surveys from different receivers I have. All taken at the same
height from prolonged surveys. WGS84 datum.
Oncore UT+ A 207,62m
Oncore UT+ B 209,24m
Z3801A 180,72m
Oncore VP A 229,95m
TBolt 207.00m
Le 10/05/2012 14:50, swingbyte a écrit :
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey
precise geolocation type gps. I was wondering if the precise timing
abilities extend to its precision in position output? I have a
thunderbolt and one of those conical white aerials from china and
would like to know if this combination will give me accurate height data.
Thanks
Tim
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On 5/10/12 6:42 AM, mike cook wrote:
A man with only one GPS ........
Surveys from different receivers I have. All taken at the same height
from prolonged surveys. WGS84 datum.
Oncore UT+ A 207,62m
Oncore UT+ B 209,24m
Z3801A 180,72m
Oncore VP A 229,95m
TBolt 207.00m
That's a pretty big variation (10s of meters), a lot more than I'd
expect (I'd expect variations more like the difference between the two
UT+s and the Tbolt).
I wonder what about the VP and Z3801 fixes pushes them so far away.
Le 10/05/2012 15:51, Jim Lux a écrit :
On 5/10/12 6:42 AM, mike cook wrote:
A man with only one GPS ........
Surveys from different receivers I have. All taken at the same height
from prolonged surveys. WGS84 datum.
Oncore UT+ A 207,62m
Oncore UT+ B 209,24m
Z3801A 180,72m
Oncore VP A 229,95m
TBolt 207.00m
That's a pretty big variation (10s of meters), a lot more than I'd
expect (I'd expect variations more like the difference between the two
UT+s and the Tbolt).
I wonder what about the VP and Z3801 fixes pushes them so far away.
May have an explanation for the Z3801A fix. I have just seen in my
notes that the Z3801A was displaying MSL and not WGS84 .
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Hi Tim,
The answer is NO. Even though decent accuracy can be had with long
averaging. It was discussed a few years ago on this list.
--
Björn
Hi all,
Hope this isn't too chat roomy, however, I have need of a survey precise
geolocation type gps. I was wondering if the precise timing abilities
extend to its precision in position output? I have a thunderbolt and
one of those conical white aerials from china and would like to know if
this combination will give me accurate height data.
Thanks
Tim
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To unsubscribe, go to
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and follow the instructions there.