question about Thunderbolt geo acuracy
Not for survey type accuracy (sub-meter, short measurement time).
The average (over a 48 hour period) was pretty good (about 1.5 meters,
RMS), but the reading over any 1 minute period can be off as much as 3-5
meters, satellite geometry dependent.
I Have two units with good antennas, mounted roughly 40 meters apart, and
after locating one of the antennas I use the second TBolt in a differential
mode and get the 1-2 meter accuracy all the time.
Michael / K7HIL
On Thu, May 10, 2012 at 5:50 AM, swingbyte swingbyte@exemail.com.au 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.
Thanks
Tim
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Attilla,
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
That is relative positions over a baseline of ca 100m. Not absolute
positions.
Björn
Hi
Just how accurate do you need?
The local survey company will get you to ~ 1 cm in roughly an hour with
"real" survey gear.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of swingbyte
Sent: Thursday, May 10, 2012 8:50 AM
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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On Thu, May 10, 2012 at 9:07 AM, Bob Camp lists@rtty.us 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.
It will give "pretty good" height data. Within a few meters but you
have to know how to translate between different definitions of "sea
level" to make best use of the data.
If you live in the USA you can now download for free the USGS
topographic maps. I'm pretty sure thy have full coverage of all of
the US. THese will have 20 foot contour intervals and you can
interpolate to at least half that. So for most normal purposes you
can find your elevation without a GPS. Just look on the topo map.
Most of these maps where made with stereo camera pairs. They get
relative elevation optically by matching the two images and then they
sent survey teams to ground check some points.
Chris Albertson
Redondo Beach, California
On Thu, 10 May 2012 17:01:48 +0200
bg@lysator.liu.se wrote:
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.
That is relative positions over a baseline of ca 100m. Not absolute
positions.
The "Baseline" is definitly larger than just 100m. the current testing
field is spread over the side of a mountain... I haven't looked at the
scale of the map, but i'd say it was somewhere in the range of 2-5km.
I do not know whether they use fixed reference stations. I am not aware
of any.
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
On 5/10/12 9:18 AM, Chris Albertson wrote:
On Thu, May 10, 2012 at 9:07 AM, Bob Camplists@rtty.us 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.
It will give "pretty good" height data. Within a few meters but you
have to know how to translate between different definitions of "sea
level" to make best use of the data.
If you live in the USA you can now download for free the USGS
topographic maps. I'm pretty sure thy have full coverage of all of
the US. THese will have 20 foot contour intervals and you can
interpolate to at least half that. So for most normal purposes you
can find your elevation without a GPS. Just look on the topo map.
Most of these maps where made with stereo camera pairs. They get
relative elevation optically by matching the two images and then they
sent survey teams to ground check some points.
And updated the elevation data with radar measurements from SRTM, as well.
On 5/10/12 9:33 AM, Attila Kinali wrote:
On Thu, 10 May 2012 17:01:48 +0200
bg@lysator.liu.se wrote:
On Thu, 10 May 2012 22:50:15 +1000
swingbyteswingbyte@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.
That is relative positions over a baseline of ca 100m. Not absolute
positions.
The "Baseline" is definitly larger than just 100m. the current testing
field is spread over the side of a mountain... I haven't looked at the
scale of the map, but i'd say it was somewhere in the range of 2-5km.
I do not know whether they use fixed reference stations. I am not aware
of any.
There are "virtual" reference stations available in a lot of places,
where they use data from carefully surveyed geodetic quality receivers
to create a synthetic reference. A common acronym is HARN (High
Accuracy Reference Network). Some are free, others have a user fee of
some sort(depends on where they are, and who set it up.)
And, of course, if you can post process, then things like GIPSY can
help. I believe the GIPSY folks ingest data from all over the world.
Le 10/05/2012 21:50, Jim Lux a écrit :
On 5/10/12 9:18 AM, Chris Albertson wrote:
On Thu, May 10, 2012 at 9:07 AM, Bob Camplists@rtty.us 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.
It will give "pretty good" height data. Within a few meters but you
have to know how to translate between different definitions of "sea
level" to make best use of the data.
I found an online WGS84-MSL converter at:
http://earth-info.nga.mil/GandG/wgs84/gravitymod/wgs84_180/intptW.htm
however for my location this gives the geoid height at 51,89m wrt MSL
and if I apply that to my Z3801A reported height it make the difference
with my TBolt even greater. I had read elsewhere , though I can't find
the reference, that the difference at my latitude is more like 30m which
would make more sense.
Can someone with a Z3801A check the result for their location?
If you live in the USA you can now download for free the USGS
topographic maps. I'm pretty sure thy have full coverage of all of
the US. THese will have 20 foot contour intervals and you can
interpolate to at least half that. So for most normal purposes you
can find your elevation without a GPS. Just look on the topo map.
Most of these maps where made with stereo camera pairs. They get
relative elevation optically by matching the two images and then they
sent survey teams to ground check some points.
And updated the elevation data with radar measurements from SRTM, as
well.
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
On 11/05/2012 00:44, bg@lysator.liu.se wrote:
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.
Well that's disappointing!
I need to measure the height of my house floor to be above the flood
plane contour. I might have a look at some dted from work. Might have
to pay a real surveyor to measure the height datum.
Thanks for all the info though guys
Tim
Go to your local building and planning commission, and get yourself
a copy of the topographical map for your address. They are cheap, and
are the standard by which everyone (insurance, zoning, ...) determines
your flood plane exposure.
-Chuck Harris
...
Well that's disappointing!
I need to measure the height of my house floor to be above the flood plane contour. I
might have a look at some dted from work. Might have to pay a real surveyor to
measure the height datum.
Thanks for all the info though guys
Tim