Geometrics G-858BP User Manual

G-858BP Backpack Mag Operators Manual
Modes of Operation
The following section discusses an overview of the modes of operation, along with their
advantages and when each should be used.
GPS Survey Mode
Used in conjunction with either Simple Survey or Mapped Survey mode described below, the
magnetometer receives GPS transmissions at regular intervals (typically every 1 second) and stores those
positions along with the magnetometer data acquired at up to a 10 Hz rate. After download into the
supplied MagMap2000 program, the GPS positions are interpolated so that each magnetometer reading is
assigned a GPS position. A GPS Wizard in MagMap2000 can reassign GPS time to both the roving
magnetometer and the base station magnetometer so that all interpolations are done with $GGA string time
in the GPS data. Reception of GPS data is signaled by a blinking RS-232 display on the Console. Quality
of GPS data is also signaled by an audio alarm if out of specification.
Search Mode
In Search mode, the magnetometer operates with analog oscilloscope-like trace of the magnetic
field data and with an audible sound whose pitch indicates changes in the field reading (the "woo-wee"
indicator). Data is not stored in memory. This is useful for manually identifying anomaly locations, much
as with a metal detector. It is also useful to check for proper sensor operation, ambient magnetic noise and
the magnetic cleanliness of survey operator accessories such as shoes, belt buckles, keys, etc.
Simple Survey Mode
This is the recommended mode for use with the Novatel GPS. In simple survey mode, the unit
keeps track of MARK (start line, and waypoints) and END LINE (end of line) key presses, and the
direction of each line. This allows a full and complete survey map to be constructed from a laid out grid.
Later, after downloading the data into the PC, after the MagMap2000 program is given the mark and line
spacing information, it will create an interpolated x and y coordinate for each reading.
Simple survey mode provides basic operation of the G-858BP, enabling the operator to easily
assign X-Y positions in the supplied MagMap2000 software. The console keeps track of which survey line
you are on, which mark position you are presently on. Operator should verify the console position and later
enter the line and mark spacing information into the MagMap2000 software to locate the readings.
Simple survey mode lends itself to interfacing to the integrated Novatel GPS system which
transmits position data as a $GPGGA string to the G-858BP Console. MagMap2000 allows positioning of
the data in either rectilinear X-Y or GPS mode.
Mapped Survey Mode
Mapped survey allows you to visualize the survey area more completely than in simple survey
mode and move around within the area in a non-contiguous fashion. Using the arrow keys, you may
position the cursor anywhere within the map and acquire data. Default cursor movements are programmed
into the unit, so if you follow a normal path across the survey area, you may simply press the MARK and
END LINE keys as if you were doing a simple survey.
This method allows the most direct positioning in the PC host software. You must enter more
information into the G-858BP console, however. This mode will track your X-Y position for you
automatically, assuming you are following a simple path, while also allowing you to change your position
manually, when, for example, you reach an obstruction and wish to start again on the other side. A Pause
Key mode may also be used for this purpose.
Base Station Mode
In base station mode, the unit will not log changes in position in either X-Y or geographic GPS
coordinates. This is most useful when the unit is being used to collect data for diurnal correction. Both
data and the time of the readings are stored in internal memory. If however you will use the GPS Base
Station wizard in MagMap2000 to reassign GPS time to both the roving and base station systems, then you
should operate the system in Simple Survey mode so that the $GPGGA time is recorded in the file.
Base station mode also supports a real-time transfer of data out of the RS-232 port as it is being
acquired. This is useful if you are using another PC to collect and process the data, for instance, when
using the G-858BP from a mobile platform. Of course, you may also store the data inside the G-858BP,
with or without real-time transfer.
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Geometrics G-858BP Specifications

General

Brand	Geometrics
Model	G-858BP
Category	Measuring Instruments
Language	English