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| Subject: | RE: GISList: GPS and powerline question |
| Date: |
02/13/2003 05:00:32 PM |
| From: |
Dan McIntyre |
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Apart from personal observations, are there any published studies that demo=
nstrate a clear relationship between the proximity of electromagnetic sourc=
es and compromised GPS performance? Seems like a cloudy issue.
Regards
Dan
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Dan McIntyre
Research Associate (GIS Analysis)
Key Centre for Tropical Wildlife Management
Northern Territory University
Darwin NT 0909
Australia
www.wildlife.ntu.edu.au
e-mail: dan.mcintyre@ntu.edu.au
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-----Original Message-----
From: Mohammad A Rajabi [mailto:marajabi@hotmail.com]
Sent: Friday, 14 February 2003 02:05
To: Gislist (E-mail)
Subject: Re: GISList: GPS and powerline question
Hi,
I have worked with both handheld and geodetic GPS receivers for over a
decade as well. In few occasions (not always) I have had problems with
powerlines.
Powerlines can be a source of trouble or not depending on the relative
position of the receiver, satellites, and the powerlines as well as the
powerline electrical specifications and the type of GPS measurement (code or
carrier phase). In other words, sometimes you can even have GPS measurement
right under powerlines without any problem provided the satellite signals is
not passing through the powerline electromagnetic (EM) field. Moreover,
carrier phase measurements are more disturbed by powerline EM field than the
code measurements as the EM field can cause a random jump in phase of the
satellite signals.
Regards
Mohammad
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Dept. of Geomatics Eng.
University of Calgary
2500, University Dr., NW
Calgary, Alberta
Canada T2N 1N4
Tel: 403-210-9497
Fax: 403-284-1980
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
----- Original Message -----
From: "Neil Havermale" <neilh@redhensystems.com>
To: "'Mohammad A Rajabi'" <marajabi@hotmail.com>: "virginia michelin"
<vmichelin@hydroqual.com>: "Gislist (E-mail)" <gislist@geocomm.com>
Sent: Wednesday, February 12, 2003 10:03 PM
Subject: RE: GISList: GPS and powerline question
I have worked with GPS for over a decade and I have never seen powerlines of
any type disrupt GPS. High power microwaves on the other hand are known to
create problems as will vegetation. The newer units are much more refined
these days in this regard. If the GPS is handheld, your body as well can
block satellites between the unit and through your body. My opinion on the
GPS "jump" you may be seeing is likely related to partial antenna blockage
by your body, i.e. a best solution satellite is blocked and a less optimal
one comes into the solution and a "jump" occurs. Best to put it on a pole
or staff as high as you head.
Temperature will also have strong affects on batteries. In some cases GPS
receivers can have temperature calibration drift but these tend to sort
themselves out the more the unit is used under various temperature regimes.
If the powerline are up there in the 15,000 volt region, there is all sorts
of leakages especially in high humidity conditions that may indeed affect
memory (operators included).
Best drop a message to Magellan directly as well.
MidNight Mapper
Aka neil
-----Original Message-----
From: Mohammad A Rajabi [mailto:marajabi@hotmail.com]
Sent: Thursday, February 13, 2003 6:07 AM
To: virginia michelin: Gislist (E-mail)
Subject: Re: GISList: GPS and powerline question
Hi,
It is the powerlines which create this problem. Try to stay away from them
as much as you can.
Mohammad
----- Original Message -----
From: "virginia michelin" <vmichelin@hydroqual.com>
To: "Gislist (E-mail)" <gislist@geocomm.com>
Sent: Wednesday, February 12, 2003 12:56 PM
Subject: GISList: GPS and powerline question
Hello All,
We use a Magellan Meridian GPS unit to gather locations and up until
recently it has worked fine. One project we are working on has us working
under powerlines, which causes data (waypoints) to be erased or shifted (we
haven't been able to determine what the shift is as the area is heavily
vegetated (low lying) and we couldn't mark points on a map). Does anyone
know whether powerline could cause these problems or if cold 20=B0 F weather
is problematic? Thanks in advance.
Virginia
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