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Dear
Colleague:
Welcome to Quantum, a periodic e-newsletter for
professionals working with magnetic technologies. Quantum
is designed to keep you up to speed on applications, case
histories, and evolutions of quantum magnetometers in a variety
of disciplines.
In this
issue:
Case Histories – Win a GEM Golf Shirt for
Your Contribution
(Top)
GEM is
seeking case histories from our users regarding magnetometers
and their applications to real-world earth science challenges or
research projects. Submissions can be very short (two to three
paragraphs), preferably with an image of data acquired in the
field.
Now is your
chance to contribute and inform your fellow earth science
professionals about the creative work that you are conducting or
interesting projects in which you have been involved.
GEM will
enter you in a drawing for a GEM Golf Shirt (1 shirt per
newsletter issue). Odds of winning are good, so please
consider contacting us at
info@gemsys.ca with your
submission!
Customer Service
- Update Your Warranty Online for Fast
Access to Updates
(Top)
GEM is pleased to offer the
longest warranty in the geophysical instrumentation industry as
a demonstration of its confidence in the quality of its
products. All GEM products are waranteed to the original
purchaser against defective parts and workmanship for two (2)
years from the date of original shipping. A summary document of
the precise TERMS and CONDITIONS is provided at
http://www.gemsys.ca/GEM_warranty_card.htm
As part of its customer service
program, GEM recently implemented an Online Maintenance
capability for all customers using its magnetometers. Click the
link above and you will also see a series of entry fields at the
bottom of the form. Simply complete the form and submit and your
warranty will be forwarded directly to us.
Then, you will be all ready for
any updates that GEM prepares – a timely way to acquire new and
upgraded features via the Internet.
With the increased activity in
airborne geophysics, earth science professionals are seeking
solutions for acquiring high-quality helicopter airborne data at
minimal cost. GEM is pleased to be able to offer such as
solution based on its optically pumped Potassium technology.
Main benefits include:
- Cost effective installation
via an integrated set of acquisition components
- Easy operation using GEM's
proven GSMP-30A acquisition console
- Elimination of costly data
systems with GSMP-30A console
- Reliable acquisition of high
resolution data via the most sensitive commercial airborne
magnetometer / gradiometer on the market
- Accurate positioning of
survey measurement locations via integrated radar and GPS data
- Rapid downloading of results
via high-speed RS-232 connection
The system can also be adapted
to fixed-wing aircraft. For details on the helicopter system,
click
here.
The following section provides a short summary of
useful / interesting links related to archaeology.
-
Benefits of Geophysics for
Archaeology
www.enviroscan.com/html/archaeological_geophysics_tabl.html#TableI
-
Geophysical Techniques for Archaeology
www.enviroscan.com/html/archaeological_geophysics_tabl.html#TableII -
-
Geophysical Guide for Good Practice (NEW)
ads.ahds.ac.uk/newsletter/issue10/geophys.html
www.archaeologic.com
archaeology.about.com
- Commercial
Site with References and
Case Histories
www.archaeophysics.com
- Leading
Archaeological Journal
http://www.archaeology.co.uk
- Internet
Archaeology Journal
intarch.ac.uk
Earthquake Prediction
- GEM Presents Paper at SEG
(Top)
GEM recently
delivered a technical paper at the Society of Exploration
Geophysicists’ meeting in Denver. This paper describes the
state-of-the-art in (electro) magnetic measurements for
earthquake research. Existing methods have met with limited
success due to limited sensitivity and long-term stability of
instruments; imperfect elimination of environmental noise; and
in the case of induction coils, to limited low frequency
features and the skin effect for their bandwidth of
measurements.
We also
analyze dipolar magnetic fields and gradients of magnetic
moments generated by earthquakes with emphasis on their strongly
local character. The magnetic moments of two measured
precursors are calculated as well as the maximum distances at
which those earthquakes can be detected with both present
methods and a new proposed method (i.e. short base Potassium
gradiometer).
Due to the
extreme sensitivity of the Potassium SuperGradiometer, the new
method is at least one order of magnitude more sensitive than
presently used induction coils. SuperGrad features and
installations are described. To access your copy of the slides
for the presentation, click
here.
Increasingly, explorationists
are seeking to use multiple combinations of sensors for
performing more complex and comprehensive magnetometer and
gradiometer surveys. This demand is based on recognition of a
number of factors, including:
- Platform options -
snowmobile, boat, towed cart, hand-operated cart
- Enhanced resolution -
closely spaced data
- Efficient definition -
structural features
- Augmentation of mapping -
sub-vertical contacts
- Determination of location -
off-line magnetic sources
- Detection and delineation -
pipe-like sources
- Integration - use of
multi-parameter surveys
The following image shows one
platform used by a major mining company for base metal
exploration and detection of pre-existing iron well-heads under
a lake.
The system employed 4 sensors
recording data to a GSM-19 rover unit. GPS information was
recorded separately in this application and then merged.
The United States Geological Survey has initiated
what is referred to as the
USGS Geomagnetism Program. The most important product of this
program is a time series record of stable
magnetometer data
having high accuracy and resolution. These requirements are key
reasons that the USGS is upgrading their systems to GEM
Overhauser magnetometer (GSM-90 EUROMAG) products.
For a description of how the USGS collects,
transports, processes, manages and disseminates magnetic
results, select
http://geomag.usgs.gov/operations.html.
To access a talk that was delivered in Mexico in October 2004
outlining the USGS’ Personal Computer Data Collection Platform,
click
here.
The multi-sensor unexploded ordnance (UXO)
detection system (MUDS) developed by Geophysical Solutions, Inc.
simultaneously deploys both the GEM Advanced Magnetometer's
GSMP-40 optically-pumped Potassium vapor magnetometer and the
Geonics EM-63 electromagnetic system in very close proximity
(1.5 meters) to one another. The system is tracked with the
receiver a high precision (sub decimeter) real-time GPS
positioning system and all data are monitored with a real-time
data acquisition system. Data from the electromagnetic,
magnetic, and positioning systems are recorded with a laptop
computer in real-time, and available on a visual display as
profile data plots, and tracking using a map-type display.
The MUDS was
developed by Geophysical Solutions to simultaneously collect
geophysical sensor data expressly for the detection of UXO. The
MUDS is capable of quickly detecting and precisely locating both
surface and subsurface UXO and will increase the safety and
efficiency of characterizing UXO contaminated sites. All
components can easily be containerized for shipment by standard
couriers and rapidly deployed to extremely hazardous sites on an
emergency response basis with a minimum of personnel.
The MUDS is
equipped with a real-time data visualization and sensor tracking
system that incorporates interactive navigation and field survey
design capabilities. All geophysical sensor data is collected
at essentially the same time and position to increase the
probability of discriminating individual UXO targets.
This innovative
approach of collecting magnetic and electromagnetic data
concurrently at small sensor separation is a significant
advancement over other systems currently deployed. The NavCom
SF-2050M is currently being deployed to track each sensor and
re-acquire anomaly positions. The NavCom receiver uses the
StarFire satellite-based augmentation system (SBAS) to obtain
sub decimeter accuracies or sub-centimeter accuracies using
real-time kinematic corrections.
Field testing
of the platform and sensors took place at two locations near
Albuquerque,
New Mexico, and at the U.S. Army Corps of Engineers UXO test bed
in Vicksburg, Mississippi. The instrument platform proved to be
robust in these field-scale tests, and the value of multi-sensor
datasets was apparent upon analyses of these data.
Figure 1. Multi-sensor
UXO Detection System (MUDS).
Figure
2: The MUDS platform in the field in February 2004.
As part of
our service to our customers, GEM regularly performs searches on
the Internet to familiarize our clients with the latest
developments in magnetics (regardless of Magnetometer supplier).
Here are some of our recent results:
Overview of WAAS Coverage
Introduction to WAAS and its Predicted
Performance
GPS World Journal
GPS Technology Plays Important Role in
Excavation of Roman Fort
GPS has
become a much-desired and valued capability among magnetometer
users. For users operating stationary observation systems, the
key value is the GPS time value used to synchronize the
magnetometer. For users of mobile magnetometers and
gradiometers, position information (in 3D) is also important.
GEM has
recently implemented new capabilities designed primarily for
mobile magnetometers. Enhancements include:
-
New data values.
Altitude and number of satellites are now reported. Altitude
is a key value for numerical modeling programs that typically
require some kind of an elevation surface (i.e. which can now
be recovered directly with the magnetometer). The number of
satellites value is ideal for the operator who wants to
evaluate the integrity of the satellite network while making
measurements.
- Standard
GPS with <1.5m resolution.
This resolution applies to the Space Based Augmentation System
(SBAS). SBAS includes the
Wide-Area Augmentation
System (WAAS), the Eurpoean
Geo-Stationary Navigational System
(EGNOS) and the MTSAT Satellite
based
Augmentation System (MSAS).
For operators who are working outside of the SBAS network
(i.e. in the far North or South), the resolution for single
point readings is 5m (Circular Error of Probability)
-
Centimetre UTM table.
GEM’s GPS values are based on WGS-84. The underlying UTM table
used to calculate GPS values now adds two extra digits. This
alleviates a problem noted when performing “walking” surveys –
consecutive measuring stations could have the same value,
making interpretation difficult. Now, each station has an
additional two digits so that each station is resolved
uniquely.
The
following are short-form notes describing typical issues to
consider before carrying out a field survey. They were written
by Dr. Francis Jones, University of
British Columbia
and have been used with permission of the author.
1. Is the Target Detectable?
2.
Search Pattern
*
Mapping of regional
behavior - do a large grid
* Rough
location - do 1 point per target size
* Precise
location - do a careful grid + secondary lines over anomalies
* Target
characterization - do >3 points per target dimension
- Probably
target geometry. For example:
* 2-D
with known orientation, or small "3-D" object
* Try to
survey lines perpendicular to long dimensions
- Usually,
the ideal survey is tempered by economics.
3. Consider Noise and Error
Sources
- Temporal variations and
instrument drift:
* Use continuously recording
base station instrument, or
* Re-occupy one station at
least once every 10 to 20 minutes
- Keep sensor clear of
magnetic objects, clothing, pockets, etc.
* Note proximity of
error-signal sources (ex. fences, power lines, etc.)
* Use acquisition procedures
that maximize consistency of readings
As an
example, imagine your task is to locate the buried pipes under
small flat field. Here some issues to consider:
- Assume for example that the area of interest is
about 100m x 30m.
-
Pipes are 2-D, and orientation may or may not
be well known.
-
What lines, line spacing, and station spacing
would be appropriate given that you have a limited amout of
time?
-
What features of the site will cause anomalies
that may interfere with the target anomalies? Buildings for
example.
-
Good note-taking is always critical,
especially if you are using older manual instruments. Don't
forget detailed comments on the site.
-
What base-station recording interval is
appropriate? Does the base station instrument have the same
sensitivity as the survey instrument?
-
Are there likely to be temporal noise sources
that are not smoothly varying? This can be a problem in urban
settings if traffic is near one area of the survey site.
-
Ideally, generate rough plots to assess regions
for more detailed surveying; either more lines or tighter
spacing?
-
Consider cross (or "tie") lines, especially if
there might be targets parallel to survey lines.
-
"Iterative survey design" is easier if the
instrument has a graphing capability built in. Then you can
start with a course grid, then survey at tighter spacings in
anomalous regions.
Magnetometer Hardware and
Firmware
- v6.0 Upgrade Delivered
(Top)
GEM is pleased to report that its Research and Development group
has recently completed an upgrade of the CPU, analog board,
backplane board and LCD. The upgrade delivers a number of
benefits to users:
-
Lower power consumption - 10 to 15% decrease
-
Reliable CPU – Fewer components, greater
reliability
-
Robust operation - Even in the most demanding
conditions
-
Lower noise – 4 times better noise
characteristics. Note that this level may or may not be
achievable in the field due to operator noise (i.e. at this
level of sensitivity, any magnetic contamination will play a
role in readings)
The v6.0 upgrade is available for new purchasers. Existing
purchasers will not be able to upgrade as entirely new
components are required.
The Last Word – Comments from Our
Customers
(Top)
As usual,
we leave the last word to our customers – our key focus in
ensuring that we continue to serve the market effectively and to
our customers’ satisfaction.
"We have recently purchased the GSMP-40
Potassium Gradiometer from GEM Advanced Magnetometers for the
Colorado School of Mines. The GSMP-40 has proven valuable for
both independent research applications and especially for
educational purposes. The ability of the GSMP-40 to rapidly
gather high quality data has helped Mines keep our students on
the leading edge of both applied and theoretical aspects of
magnetic and magnetic gradient methods for geophysical
exploration. Likewise, the gradiometer has proven valuable for
quickly identifying underground utility targets on the Mines
campus, where construction plans require knowledge of these
targets in advance.
In addition to the quality of the GSMP-40 gradiometer, I have
found the quality and service of GEM Advanced Magnetometers
staff to be wonderful. They have taken all comments, questions,
concerns and requests seriously and have acted in a timely maner
on each. In particular, they have gone above and beyond
traditional support center obligations by immediately modifying
the magnetometer's software design at our request to improve
data output quality and ease of teaching for large numbers of
students."
Richard Krahenbuhl
Ph.D. Candidate
Colorado School of Mines
"We took our GSMP-40 to North Dakota for a field project this
summer and
it worked wonderfully. Our intent was to compare the data
recovered with the
GSMP-40 to that recovered with a fluxgate gradiometer earlier.
The GSMP-40
was MUCH faster and collected the data in a fraction of the
time."
Dr. Tommy Ike Hailey
Northwestern State University
"We have four of your Overhauser magnetometers, GSM-19
(Standard Overhauser) and GSM-90 (EUROMAG). We are very
satisfied
with them, and are now considering buying more."
Bjorn Ove
Auroral Observatory
University of Tromso
"We have had the GSM-19T (Proton) instrument for
the last 5 years. It is giving very good results."
Dr.Vinit
C. Erram
Indian Institute of Geomagnetism
"Good website!"
Jamal
Mbarak
Shatry Gems Ltd.
Important Note: Our goal is
to only communicate with people who would like to hear from us.
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Copyright 2004. GEM Systems, Inc. Advanced Magnetometers.
All rights reserved with the exception of organizations that
have contributed links to this issue. Our thanks to the contributors who have
made this edition possible, and who are identified in the text of related articles
or through their company websites. Note that some quotes relating
to industry-specific trends may have been obtained from public-domain
sources, and are not intended to promote GEM Systems,
Inc. Other examples may not necessarily reflect GEM products;
rather these examples are intended to illustrate the use of
magnetics and magnetometry for selected applications.
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