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TESTING THE ARCHER…
We are in the final phases of testing the Archer™ from Juniper Systems:
http://www.junipersys.com/main.cfm
So far it seems to do the job as well as the Trimble Recon™ we have been using
until now. Send us your opinion…
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SURVEY NEWS:
• Canadian
Differential GPS Service Secures Funding (March 13, 2007)… see hereunder…
• Announcement concerning the publication of the NAD
83 (NSRS2007) National Readjustment Coordinates.
NGS recognizes that the primary method by which NSRS monument coordinates are
accessed is via the NGS datasheet format. However, the software for making the
re-adjusted coordinates and their associated local and network accuracies is
not yet ready for public use. Rather than provide a sub-standard service to
its stakeholders, NGS has decided to release the re-adjusted coordinates with
local and network accuracies in a simple text-based format for immediate use.
NGS expects this data to be available on datasheets before the end of March
2007. An announcement will be made on the NGS home page when this service
becomes active.
www.ngs.noaa.gov/NationalReadjustment
• KML Search now available
in Google. KML Search means that Google, in addition to searching many other
file types (DOC, PDF and PPT, for example), can now search inside KML/KMZ
files. (KMZ is a compressed form of KML. For most purposes, they are
interchangeable.) KML files are basically text files with a certain structure
–ID & position -, nothing more…
www.directionsmag.com
• Need to locate a place in the USA, and know
only its name? use the USGS Geographic Name Information System:
http://www.geonames.usgs.gov
SEISMIC NEWS:
• Wonder how seismic companies
stocks compare? It’s a breeze thanks to the PGS website (check each
company’s box).
www.pgs.com
• See our own Seismic Crew Locator on our
web site, or email us to get a kml format file of
seismic crews and vessels. If you want us to provide a more accurate position
for your crew, please contact us…
www.zupt.com
OTHER NEWS:
• Draper’s
Inertial Stellar Compass is now fully operational… this represents the
first use of a MEMS gyro in a complete spacecraft attitude determination
system…
www.draper.com
• D-TRADE
Web Site of the US
State Department… has had some hiccups since January.
In short, the change to Electronic Forms such as DSP-74 to Amend a DSP-73
temporary Export License crashed the system in January. So you still have to
use the ELLIENet electronic system to file a
DSP-119 to amend export licenses until the problem is fixed…
http://www.pmddtc.state.gov
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SURVEY TIPS:
How to use the NGS NOAA OPUS web site to establish high quality GPS
control with only one GPS receiver.
• For short datasets we can now use
the new “OPUS Rapid Static” (Jan-2007) option except during high ionospheric
disturbances (Geomagnetic Storms)…
• The classic OPUS using the
“Pages” program requires more than 2 hours of static data on the point to
survey.
• Antenna height must be measured
in meters to the “Antenna Reference Point” of your GPS antenna and not to
your L1 phase center! The difference is important and ARP differs for every
antenna.
• “The ARP is almost always the
center of the bottom-most, permanently attached, surface of the antenna”… (basically it is the bottom of the metallic 5/8” nut).
• See their site for your own
antenna calibration values: www.ngs.noaa.gov/ANTCAL
• For the rest just punch in your
email address and upload your file, and they will send you the results with a
few centimeters accuracy within a few minutes (it is impressive)…
www.ngs.noaa.gov/OPUS
How not to use GPS with Inertial Navigation…
• It is very important to remember
the negative effects of multipath on GPS solutions. Multipath is a deflection
of the radio signal coming from the satellites caused by trees, vehicles and
buildings etc… Your GPS receiver will be unable to warn you of the presence
of multipath and therefore will show a good QC value for your position even
if it is off by 10, 20 meters or more!...
• A GPS point is not good because
it has an internally computed QA/QC code that is good. It has to be surveyed
following very careful rules and procedures: correct Antenna Height (measured
2 or 3 times), enough data, good constellation and no temporary or permanent
obstacle around or above the antenna. Bad control means bad inertial survey…
The necessary art of the check shot…
• Any GPS receiver will provide a
correct position within a few meters or tens of meters if used correctly in
an “open” area in non differential mode. It is true if I use a $15000 or a
$100 receiver. That’s good.
• An inertial system on the other
hand can give a position that is 2000 km off or more when initialized on the
wrong point. That’s bad.
• The reason is that a GPS receiver
by itself is an “absolute” positioning system: its accuracy is rarely
worse than 20m except close to a cliff or in urban canyons where all bets are
off (these are Stand alone accuracies).
• The inertial system on the other hand
can be centimetric but it is a relative system: if you feed it a start
position that is wrong (in particular in longitude) it will align and
navigate happily in the wrong place, and you won’t know anything about it,
unless you do a check shot!
• So always do a
check shot on a point surveyed from a separate traverse than the start
point. Even better: surveyed with a different technology (Static GPS or RTK,
Optical or another INS traverse). The check doesn’t have to be extremely accurate, we are just trying to avoid blunders…
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IN THIS ISSUE:
• News
• The Backpack today
• Suggestions
• Inertial & other survey tips
• Seismic info
• The rest of the World
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ZEST - A
monthly newsletter providing information, tips, insights and commentaries on
the use of Zupt inertial navigation systems, other inertial systems, and
their software, bug tracking, navigation in general, seismic survey, the use
of GP Seismic™, and internet links etc
To subscribe,
email us at:
jg@zupt.com
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SUGGESTIONS FOR IMPROVEMENT:
• Upgrade to the latest version
of GPSeismic™ and interface directly with QuikLoad for the creation
of zgw files and QuikView
for the processing of zgs
files.
( www.gpseismic.com ).
• Maxie
Phillips of M&N Services already suggested an improvement to the ZUPT
INS viewer in GPSeismic, it will now show meters and feet.
• ATTRIBUTES… soon we plan to implement the
optional creation of automatic attributes in the comment field of our
records.
An attribute is a fixed code, which can be interpreted by a GIS or Mapping
software or referred to within QUERIES in the Microsoft Access™ database
for example (i.e. GPSQL™).
Here is a sample of attribute codes suggested by John Curkan
and Doug Wiggill:
NP = No Permit, BLDG = Building, CRK = Creek (stream etc…), TRRN = Terrain,
PWL = Power line, HZD = Hazard, OPL = Oil Pipeline
, WW = Water Well, FNC = fence, TRAIL = trails & dirt roads etc…
Please send us your own suggestions.
• The Bluetooth wireless
connection between the B-PINS (our backpack) and our data collector has
been improved recently when we switched to a
Virtual Port
on the DC to handle the communication. This will be available in upcoming
version 2.0 of Zing™…
• Ultra Mobile PC (UMPC) computers
are possibly becoming a standard in mobile computing, in particular after
their success at the CES 2007 show in Vegas. They have a larger screen than
PDAs, they are designed to run on batteries and
some of them are quite rugged.
These UMPCs
might have some advantages when operating in a boat, an aircraft
(helicopter) or land vehicle (truck, 4-wheeler, buggies)… The driver can
see their screen better than with the Trimble Recon™ etc…
If you are interested in a larger
display please contact us…
We can send you the excellent article
“The UMPC at the end of 2006” by Geoff Walker on demand…
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INERTIAL SURVEY TIPS:
Inertial Integration. The difference between loosely coupled and
tightly coupled navigation systems is paralled in computer and server designs
as in this text from the IBM Informix Dynamic Server web site:
http://www.publib.boulder.ibm.com
Of course in Inertial Navigation, an Integrated system (say INS / Acoustic)
is loosely coupled if the solutions are shared (i.e. acoustic
positions sent to the INS), which implies that each system has enough beacons
or sensors to be able to work independently (enough acoustic beacons to triangulate).
The system is tightly coupled if the raw data are shared and
integrated properly into the navigation solution (i.e. the acoustic ranges or
line of position). In this case a single LOP would aid the INS navigation,
while it wouldn’t be useful to the acoustic system independently.
Of course there is the deeply coupled solution as well, where the
navigation system in turn helps to acquire or improve the raw data
from the sensor...
SEISMIC INFO…
• Source Point Offsets. Some
seismic 3D grids can be defined in complex terms by the client and his
intentions may seem rather obscure to the surveyor, until the problem is
looked at from the usual inline / lateral offset situation, and everything
becomes clearer…
it used to be that 3D seismic grids were all perpendicular (source lines were
oriented at 90 degrees from receiver lines), and if a source point couldn’t
be located in its preplot location, it had to be moved “right” or “left” and
“up line” and “down line” in integer numbers of intervals.
For example if source and receiver intervals were 220ft, you could offset a
point 440ft right and 220ft up line, or 660ft left and 880ft down line…
More and more 3Dseismic grids are oblique now, and that means that the
receiver line doesn’t intersect the source line perpendicularly but at other
angles (i.e. 45deg or other angles).
Here is a recent example were the client stipulated the following rules if a
source point had to be offset (in order of preference):
Rule 1: move the SP 27.5ft in any direction.
Rule 2: move “inline” along a 55ft corridor to within 3 stations
spaces of the next source line, up to 1017.5ft.
Rule 3: move “crossline” 880ft and inline
(following inline
rule)......
Turns out these offsets can easily be done following the usual inline /
lateral offset rules for oblique grids where we move the SP inline (in the
direction of the source line) and laterally (in the direction of the receiver
line) by the allowed distances.
By the way, our new field software Zing™ v2.0 can now handle inline/lateral
offsets for all types of grid.
Save money, save the environment, be safe…
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Lake Tests of Zupt Underwater Vehicle Navigation
system…
Canadian Differential GPS Service Secures Funding
(March 13, 2007)
Canada’s Differential GPS (CDGPS) correction service
received a timely commitment from federal, provincial and territorial government
sponsors to continue its nation-wide broadcasts improving GPS accuracy until
at least 2010. CDGPS typically
improves mobile GPS horizontal accuracy to about one metre
at 95% confidence across the entire Canadian land mass and adjacent offshore as
far north as 75º. It is the only such
service covering Canada
from coast to coast to coast.
For more information,
visit http://www.cdgps.com/e/index.htm or
contact general.manager@cdgps.com
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The rest of the world…
GPS Denied Navigation Research with SLAM (U. Of Sydney):
www.acfr.usyd.edu.au
…did you know that inertial technology can be used for positioning
firefighters and other first responder crews inside buildings with no
visibility, no comms and no RF…
Useful site of the month (to compute GEOID03 separations):
www.ngs.noaa.gov
Graphically cool site of the month (high speed connection):
www.foret-bleue.com
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Last word
You can find our previous newsletter
on our web site. Please let us know what you would like to see in a
newsletter. Send us info, tips, suggestions, links,
pictures etc… let us know if you want your questions or comments to remain
private or to appear in the newsletter. Circulate it around, and /or give us
email addresses of others who would like to receive it.
No images? visit our online newsletter
@: zupt.com
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Find our link “Feedback” under Contacts on our web site. Please use it to
send us any info, not only on bugs in our software, but suggestions etc…
www.zupt.com/feedback
See you soon!
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