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Geometrics Geode EM3D Operation Manual

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Geode EM3D
p/n 68002-01 REV. D
Operation Manual
For
Geode EM3D running
GeodEM
Ver. 3.0
COPYRIGHT © 2018
GEOMETRICS, INC.
2190 Fortune Drive, San Jose, CA 95131, USA
Phone: (408) 954-0522
Fax: (408) 954-0902
support@mail.geometrics.com
www.geometrics.com
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Summary of Contents for Geometrics Geode EM3D

  • Page 1 Geode EM3D p/n 68002-01 REV. D Operation Manual Geode EM3D running GeodEM Ver. 3.0 COPYRIGHT © 2018 GEOMETRICS, INC. 2190 Fortune Drive, San Jose, CA 95131, USA Phone: (408) 954-0522 Fax: (408) 954-0902 support@mail.geometrics.com www.geometrics.com...

  • Page 2: Table Of Contents

    Network Interface Box (NIB)-------------------------------------------------------------------1 GEM3D Receiver----------------------------------------------------------------------------------3 Magnetic induction coils------------------------------------------------------------------------5 Electrodes------------------------------------------------------------------------------------------6 Ethernet cables-----------------------------------------------------------------------------------6 Chapter 2: Geode EM3D PC Controller setup------------------------------------------------------8 Chapter 3: GEM3D receiver setup-------------------------------------------------------------------11 Chapter 4: Software-------------------------------------------------------------------------------------18 Chapter 5: SAS (System Acquisition Software) --------------------------------------------------31 Chapter 6: Interface to a controlled-source transmitter -------------------------------------33...
  • Page 3 Appendix 2: GPS Setup Software -------- -----------------------------------------------------69 -----------------------------------------------------------------69 Appendix 3: MT Theory...

  • Page 4: Chapter 1: System Components

    Chapter 1: System Components A. Introduction: basic theory of operation, networking, and data acquisition The Geode EM3D is a distributed network of EM receivers. Each receiver has six channels which can be configured with up to three magnetic (H) channels and from three to six electric (E) channels, depending on the number of magnetic channels used.
  • Page 5 Fig. 3: GEM3D receiver box 4. Magnetic Induction Coil: The Geometrics G20K coils operate on a band width of 0.1 Hz to 20k Hz. The operation range of the Geode EM3D CSAMT system is 0.1 Hz to 10 kHz. Coils specifications are available at www.geometrics.com...

  • Page 6: Electrodes

    Geometrics. Fig. 5 Stainless steel electrode and cable 6. Ethernet Cables: The Geode EM3D uses a proprietary Ethernet cable that is specially ruggedized for field use. It also has an isolated “trigger” wire to synchronize all receiver channels on the network without concern for any delay...
  • Page 7 Fig. 6: Ethernet cable with 10-pad connectors on each end. GPS with cables: Synchronization between the CSAMT transmitter and the Geode EM3D receivers is through scheduler software using GPS time on the transmitter and PC Controller. There is only one GPS unit to control all GEM3D...

  • Page 8: Chapter 2: Geode Em3D Pc Controller Setup

    GPS with antenna and USB cable and GPS driver software, a Network Interface Box (NIB), an Ethernet cable to the nearest GEM3D receiver, and the controller software. Ruggedized PC: The Geode EM3D uses a commercial laptop computer specially adapted for field use operation.
  • Page 9 Figure 8: Network Interface Boxes; single-line (left). Figure9: Front panel of Network Interface Box. In addition to being an adaptor, the NIB performs the function of powering the GEM3D receivers up and down. Refer to the above figure. Prior to starting SAS, switch to the Enable Power Up position. This will power up a portion of the acquisition board on the first GEM3D on each line, enabling them to respond to software commands.
  • Page 10 Installation of required software onto Controller: All required software should have been pre-installed on the PC Controller from the Geometrics factory. The following information is only required if the software must be re-installed. e. SAS (System Acquisition Software) GPS software and drivers g.

  • Page 11: Chapter 3: Gem3D Receiver Setup

    Chapter 3: GEM3D receiver setup. Connecting to the GEM3D receiver: The GEM3D receivers have panel connections for the power, Ethernet cables, ground, E-field dipoles, and magnetic sensors. We will look at each individually: A. Panel-1 Electric field terminals Fig 10: GEM3D receiver E-field (telluric) connectors Perhaps the most difficult part of setting the connections to the GEM3D receiver is properly connecting the electric dipole cables to the terminals.
  • Page 12 Fig. 11: connecting telluric lines (E field) B. Panel-2 Magnetic field terminals Fig. 12 Channel 4 = Hz, Channel 5 = Hx, Channel 6 = Hy...
  • Page 13 Fig. 13: Hy and Hx connected disabling E channels 6 and 5 respectively There are three magnetic field channels on the GEM3D Receiver box. These are labeled from left to right as Hz/CH4, Hx/CH5, and Hy/CH6. If a coil is plugged into Hy the E-field channel CH6 is disabled and the H-field channel Hy/CH6 is enabled.
  • Page 14 There are two 12V power connectors. There is no internal battery so all power must be supplied by an external 12V battery. Having two power connectors allows the operator to swap batteries without turning off power to the receiver. The blue Ethernet LEDs flash at a rate of once per second when the Ethernet board is powered up (fast flash powered up mode).
  • Page 15 D. Electrodes and electrode cables: Non-polarizing porous pot electrodes are recommended. The Geode EM3D does not use electrode buffers since calibration is done real-time in the field. There are nine electrode terminals as pictured in Fig. 10. The red terminals are considered to be positive by the software.
  • Page 16 The function of the GPS receiver is to synchronize the CSAMT transmitter with the GEM3D receiver acquisition. It is also used to set the PC Controller clock. The Geode EM3D scheduler software creates a file that sets all the transmission parameters including the start time of the transmission.
  • Page 17 H. Data acquisition: See section K.2. Software/GEM3D Controller Software. Transmitter: See the manufacturer’s manual or the make and model of the CSAMT transmitter you are using.

  • Page 18: Chapter 4: Software

    Chapter 4: Software There are three software programs that must be installed for Geode EM3D acquisition operation. These are SAS (System Acquisition Software), GeoEM2010 which is the user interface software, and the GPS driver software. The current GPS is manufactured by GlobalSat, but this may change as GPS technology changes so contact Geometrics, Inc.
  • Page 19 operator to use a previous setup as the starting template for the new survey. iii. Open GTS file: The GeodEM2010 software creates a data file from a series of SEG2 files. The extension of the data file is .GTS . Opening a GTS file will display time series on the screen.
  • Page 20 Fig. 19: GeoEM 2010 Setup menu i. General 1. Survey block: General information about the survey site. 2. Coordinate System/Coordinate Parameters: General GPS coordinate information 3. Line Frequency: Set powerline harmonic filter (50 or 60 Hz) 4. Auto Line Freq Detection: Automatically sets powerline frequency filters.
  • Page 21 ii. Frequency stepping: This screen allows the operator to set up a frequency schedule for both the CSAMT transmitter operation and the receivers’ acquisition. Fig. 21: Setup menu – Frequency stepping 1. Maximum frequency (Hz) 2. Minimum frequency (Hz) 3. Frequencies per octave 4.
  • Page 22 7. Stepping cycle: This is the amount of time to go through all the frequencies. It needs to be set to provide at least the minimum time to run through all the frequencies. If it is not set with enough time for all frequencies the lowest frequencies will be truncated or dropped.
  • Page 23 Fig. 22: Setup menu –Patch Setup Patch Setup is to configure each channel on each GEM3D receiver in the active survey section 1. Patch Name: This is the name of the survey and is used to name the acquired data files. NOTE: In order for the GeoCSAMT or MTPro processing software to create a continuous line when the stations are rolled to a new position the Patch Name must be change for the new...
  • Page 24 in a serpentine shape to create multiple parallel lines. No LTU modules are used. 7. Geode Configuration of Segment 1: Allows the user to set or view the channel configuration for each GEM3D receiver in the segment (line). There is only one segment for the GEM3D setup.
  • Page 25 Fig: 30: GPS menu The menu displays the supported GPS for synchronized triggering of acquisition to the CSAMT transmitter. In this example “UBlox GPS but other GPS receivers can be used. v. Start SAS: Starts the background acquisition software: This will load the receiver acquisition software and display a noise monitor as pictured below: Fig 23: SAS Noise monitor menu...
  • Page 26 ix. MT Acq. and Processing Fig. 25: Acquisition menu 1. Sample rate of 24 kHz, 3 kHz, and 93.75 Hz defines the number of samples per second for the three acquisition frequency bands. The “Record Length” specifies how long, in seconds, each time series will be at the specified sample rate.
  • Page 27 9. Use CTL-DEL to remove a time series. How to review and edit time series after acquisition:  To read in a previously recorded data set start GeodeEM and go to “File-Open GTS File”.  Navigate to the folder where the acquired data is stored and select the desired .GTS file.
  • Page 28 xiii. CSAMT Acquisition: This starts CSAMT acquisition based on the schedule set up in the “Setup/Frequency Stepping” menu. Once CSAMT acquisition is started the following screen is displayed. The number of channels displayed was set up in the “View/Display Parameters” menu. If there are more channels acquired than displayed the left-right arrow keys will display additional channels.
  • Page 29 You can mask out a set of time series simply by pressing the DEL key. In older versions of the software it greyed out the time series traces. In newer versions the masked time series traces become red xiv. View: 1.
  • Page 30 to set both E-field gains the same and both H-field gains the same. ii. CSAMT Acquisition Simulation: This injects a predetermined test signal into each channel for acquisition simulation. Starting a true acquisition will stop simulated acquisition. This feature is disabled in the current software version.

  • Page 31: Chapter 5: Sas (System Acquisition Software)

    Chapter 5: SAS (System Acquisition Software) The SAS noise monitor allows you to view activity on the selected channels before, during, and after acquisition. Also refer to section “Chapter 4 Software, 2 GEM3D Controller setup, b Setup, IV Start SAS” Fig 32: SAS noise monitor Clicking on “System”...
  • Page 32 SAS commands available from SAS noise monitor window: There are a number of useful functions available through the System Operating Software (SAS) that can be accessed through the SAS Noise Monitor window. The SAS noise monitor is the only SAS window seen in the EM version of SAS.

  • Page 33: Chapter 6: Interface To A Controlled-Source Transmitter

    Chapter 6: Interface to a controlled-source transmitter Interface to a controlled-source transmitter a. Geode EM3D schedule software: The GEM3D Scheduler file is created under the “Setup/Frequency Stepping” menu in GeodEM 2010 software. The details of the frequency stepping menu is discussed in section “K-2-b-ii” of this manual.

  • Page 34: Chapter 7: Csamt Processing

    Chapter 7: CSAMT Processing with CSAMTPro GeoCSAMT processing software is used to process the CSAMT raw acquisition data to impedance and phase. Installing GeoCSAMT: Fig.34: CSAMT processing software menu Processing Steps: After acquisition of either scalar or tensor CSAMT data the results can be processed to create impedance, phase, and other parameters.
  • Page 35 4. Navigate to the data files previously set up in the Data Folder field in the Geode EM2010 program under Patch Setup. 5. Select anywhere from 1 to multiple CSAMT data files by doing a Ctrl-click on each one. Then click “Open”. The following window will be displayed. Fig35: Adding file for processing menu NOTE: In order for the GeoCSAMT or MTPro processing software to create a continuous line when the stations are rolled to a new position the Patch Name must be different for each...
  • Page 36 6. To change the array type click on “Array Type” to select any of Scalar, Tensor, Vector, or 2H Scalar array for processing. 7. Click “OK”. Fig.36: Sample CSAMT processed impedance curve 8. Apparent resistivity, impedance phase, and a number of other processed displays can be chosen by clicking on the “Plot Type”...
  • Page 37 These edits only mask out the selected data points. They are not deleted. In order to save the edits the data must be exported by clicking on “File” and selected the desired export format, as explained below. You can also edit the individual stacks for each frequency. Right click on any frequency to see the individual stacks.
  • Page 38 Exporting CSAMT data from CSAMTPro to third-party inversion program.: After importing the GTS file(s) and seeing the impedance curve click on “File”. You will see a list of possible file types for export. To export a GeoCSAMT data file to Zonge Geophysics’ SCS2D inversion program for CSAMT data select “Export to Zonge “.AVG file”.
  • Page 39 Figure 1 Assuming we got 2 GTS files (GuanCSAMTTensorTest.GTS and GuanCSAMTTensorTest(1) ) . Run CSAMTPro program and select “Add GTS files…” menu (Fig2). Make sure the Patch Names are identical for same setup, array type is “CSAMT Tensor” and the Tx No. is correct for each GTS file.
  • Page 40 Figure 2 Figure 3: Note that Zxy impedance (X-direction) are the red squares and Zyx (Y-direction) are the blue diamonds. : Note that X-direction resistivites are the red squares and Y-direction resistivities are the blue diamonds. Bostic transformation The Bostic transformation of CSAMT data is a point-by-point conversion of apparent resistivity and depth to true resistivity and depth.
  • Page 41 2) Similar to MTPro, database save and open features are added to CSAMT program ( Figure 4).
  • Page 42 1. Click on HELP then ABOUT MTPRO. You will see a menu pop up with the fields “Computer ID” and “License key”. There will be a code “Computer ID” field. Copy and Paste this code into an email message and send it to support@geometrics.com and/or wfei@geometrics.com 2.
  • Page 43 Fig. 37: AMT processing software menu After acquisition of AMT data using GeoEM2010 the results can be processed to impedance, phase, and other parameters. Do the following: 1. Click on “File”, “Add GTS Files”. 2. A new window will pop up. Click on “Add GTS Files” 3.
  • Page 44 Fig. 38: Select files to be processed NOTE: In order for the GeoCSAMT or MTPro processing software to create a continuous line when the stations are rolled to a new position the Patch Name must be different for each setup. If the Patch Name is the same, the processing software will average them together. You will see a list of soundings based on the number of Ex stations in the file.
  • Page 45 The station Easting, Northing, and Elevation are the center of the E-field dipoles and the position of the H-field sensors. 5. Click on OK. To see the following display. 6. Apparent resistivity, impedance phase, and a number of other processed displays can be chosen by clicking on the “Plot Type”...
  • Page 46 7. The edit button to the far left of the screen will allow editing of the displayed data. After selecting the edit button a right mouse click will swap the X-direction (Zxy) and Y-direction (Zyx) points. Clicking the left mouse button on a data point will mask out the that data point.
  • Page 47 Bostick transform of AMT data to true resistivity and depth: Note that X-direction resistivites are the red squares and Y-direction resistivities are the blue diamonds. Parallel Test Noise Calculation: The parallel test noise calculation allows the user to do a basic field test of the noise level comparing any two pairs similar parallel sensors.
  • Page 48 However, the most commonly viewed tipper functions are the magnitude and phase, as shown below. For the Geode EM3D the vertical magnetic field, Hz, is generally measured by the G100K high- frequency coil. The lowest practical frequency of the G100K coils is 10 Hz. Therefore, the practical range of tipper values is between 10 to 20,000 Hz.
  • Page 49 Tipper phase: Note that Tx (X-direction) are the red squares and Ty (Y-direction) are the blue diamonds. How to combine two files with different names to process them as a single file: If you have two files with different patch names but you want to combine them as a single sounding you need to rename one of the files to they both match.
  • Page 50 Selected files After editing array names...
  • Page 51 Result of both files processed together Sensor Noise Test: In order to do a sensor noise test you must compare the sensors parallel to one another. For example if you have two receivers and Hy1 and Hy2 you can do a noise test for Hy1 and Hy2. It is the same for Hx1 and Hx2 or for Ex1 and Ex4 (if you have three Ex channels on each receiver).
  • Page 52 The relatively high low frequency noise in the graph above is the result of using metal stakes in the ground instead of porous-pot electrodes. At low frequencies below 1 Hz porous-pot electrodes are preferable for noise measurements.

  • Page 53: Scalar Processing

    Scalar Processing To process the data as scalar data when adding GTS files change the click the “Array Type” menu arrow and select “Scalar MT”. This will allow MTPro to process the data as scalar only. Example above of processed scalar data. Exporting EDI files from MTPro...
  • Page 54 In order for MTPro to export Edi files it must be at least version 3.0 The GTS file must have been acquired in GeodeEM version 3.0 or greater. If the GTS file came from an older version it can be opened in version 3.0 or greater and edited to add the correct offset. AA.
  • Page 55 The 10 character limit is unique to WinGLing. Other programs reading EDI files may have be able to accept longer file names. 4) Enter a latitude and longitude reading for one of the stations. Use the negative singe (-) for latitudes in the southern hemisphere, and longitudes in the western hemisphere.
  • Page 56 6) Click “Export EDI Files” 7) Navigate to the folder and location where you want the EDI files stored and click OK. The save file name will be the will be the EDI Data ID with a “.EDI” extension, for example “day1- Ex1.EDI”.

  • Page 58: Chapter 9: Factors Determining Good Versus Bad Data For Controlled-Source Audio Magnetotellurics

    Natural-field telluric currents can also be considered noise. The Geode EM3D CSAMT acquisition software uses a proprietary filtering technique to narrowly band limit the acquired frequencies to match the frequencies of the transmitter. Data quality determinates can be: A.

  • Page 59: Chapter 10: General Survey Principles And Typical Survey Operation

    Chapter 10: General survey principles and typical survey operation: A. There are three general areas of running a Geode EM3D survey. Planning, laying out the survey line(s), and data acquisition. It is important to note the following: On starting a survey line the first Ex electrode should be positive side of the dipole.
  • Page 60 Chapter 11: Notes on AMT (natural field) versus CSAMT (controlled source) The difference between CSAMT and AMT acquisition is that in MT (magnetotellurics) or AMT (audio magnetotellurics) only natural field signals are used. In CSAMT (controlled-source audio magnetotellurics) only the transmitter signals are used. Details of the mathematical basis of MT theory is given in Chapter 12 below.
  • Page 61 1. The use of a controlled-source transmitter will provide signal without worrying about the time of day, weather conditions, etc.. It is always available and tends to be relatively strong compared to natural-field signals. 2. Because the receiver can be band limited to acquire only the exact frequency of the transmitter, you can work in more noisy environments than is possible with traditional MT and AMT.

  • Page 62: Appendix 1: File And Data Structure

    1; Byte 6(Unsigned Integer): Number of segment. The segment concept comes from 3D seismic layout. It is normally 1 and a maximum 2 without an LTU in Geode EM3D. Byte 7(Unsigned Integer): Number of Boxes in the layout.
  • Page 63 Byte 33,34,35,36(Unsigned Integer): Minimum seconds of per frequency; Byte 37,38,39,40(Unsigned Integer): Minimum cycles of per frequency; Byte 41,42,43,44(Unsigned Integer): Minimum records of per frequency; Byte 45,46,47,48(Unsigned Integer): Requested Frequency stepping reference seconds from 00::00::00 of current date; Byte 49,50,51,52(Unsigned Integer): Frequencies per octave( either 1 or 2) Byte 53, 54, 55,56,57,58,59,60(Unsigned Integer): Actually reference time in seconds from 00::00::00 of 1/1/1970 Byte 61, 62,63,64,65,66,67,68 (8 bytes IEEE Float, sign bit, 11-bit exponent, 52-bit mantissa):...
  • Page 64 Byte 157, 158, 159,160,161,162,163,164,165, 166, 167,168,169,170,171,172 (ASCII character string): The latitude string from GPS near controller in format “HDDMM.mmmmm”, i.e. N40°56.93172' Byte 173,174, 175,176,177,178,179,180,181, 182, 183,184,185,186,187,188 (ASCII character string): It is the longitude string from GPS near controller in format “HDDDMM.mmmmm”, i.e. W140°56.93172’.
  • Page 65 Freq1_RealRsp1_Imag_Rsp1…. Freq2_RealRsp2_Imag_Rsp2” Byte 6(Unsigned Integer): Number of segment. The segment concept comes from 3D seismic layout. It is normally 1 and maximum 2 without LTU in Geode EM3D. Byte 7(Unsigned Integer): Number of Boxes in the layout. Byte 8(Unsigned Integer): Number of channels in the layout.
  • Page 66 Byte 0 (unsigned integer): Number of channels used in the box. Byte 1 (unsigned integer): Box configuration type: 0- unknown, 1-6Ex, 2-5Ex1H, 3-5Ex1Ey, 4- 3Ex1Ey2H, 5-2Ex1Ey3H Byte 2 (unsigned integer): Number of Ex channels used in the box. Byte 3 (unsigned integer): Number of Ey channels used in the box. Byte 4 (unsigned integer): Number of Hx channels used in the box.
  • Page 67 Byte 103-110 (8 bytes IEEE Float, sign bit, 11-bit exponent, 52-bit mantissa): contact resistance Byte 111-118(Unsigned Integer): Contact resistance measurement time in seconds from 00::00::00 of 1/1/1970 3) Record Block Record Tag sub-block Byte 0-1(unsigned integer): Each record block starts with Record ID, 5354H, which identifiers the start of a record.
  • Page 68 Record data is stored in 4 bytes IEEE floating point (sign bit, 8-bit exponent, and 23-bit mantissa). The record data is stored channel by channel. The bytes of each channel are 4 X number samples (bytes 29-32 in record tag).
  • Page 69 Appendix 2: GPS Setup software GPS Setup software: GPS timing is used to synchronize the GEM3D receiver and the transmitter in CSAMT mode. GPS synchronization is not required in the AMT mode since the transmitter is not used. In CSAMT acquisition the GPS is connected directly to the controller PC which in turn synchronizes the individual receiver boxes to a common time based on the scheduler program.
  • Page 70    where we have also assumed that there is no free charge present ( E = 0). Equation (5) is the Ñ· Helmholtz equation for E and k is the propagation constant. The source of MT signals is in the atmosphere where the conductivity is near 0, and here the propagation constant is ...
  • Page 71  from the plane wave source. This implies that represents the amplitude of a reflected wave, and in a uniform earth where there are no reflectors, its amplitude must also be zero. So        ...
  • Page 72 The presence of uniform plane-waves implies that the wave’s source is distant: nearby sources are likely to generate waves with a spherical wave front that will not be uniform in the survey area. If sources are nearby, equations 1 and 2 are incomplete; they lack the appropriate source terms for a complete description of the fields and their interaction.
  • Page 73 Equating E and H fields at z = 0 yields              The solution of these equations yields the amplitude of the transmitted wave and the reflected wave:  ...
  • Page 74 Modern magnetotelluric systems are designed to record variation of both the electric and magnetic fields in two orthogonal directions and use these records to calculate the surface impedance at a measurement site. The surface impedance Z is complex, frequency dependent, and, due to the presence of noise and earth structures, is also a tensor: ...
  • Page 75 is an average cross power density spectrum and Ex is the discrete Fourier transform of the measured field Ex. The (*) symbol indicates complex conjugation. The two cross power expressions above combine to yield       and expressions for Zyx and Zyy are obtained in a similar way.

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