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A seismic wave front emanates from an energy source like ripples on a pond, but in three dimensions. It is the Surface connecting points of equal travel time from the source. In a homogeneous medium, a Surface drawn through points of equal travel time is spherical, as depicted in the animation below. The seismic trace, which is what is recorded by the seismograph, represents particle motion vs. time. In a homogeneous medium, the wave front can also be described as a Surface of constant phase. There are four main types of seismic waves, each characterized by its specific particle motion: Compressional Waves (“p” waves) are identical to sound waves – the particle motion is parallel to the propagation direction: p-wave animation by L.W. Braille, Purdue University. Shear Waves (“s” waves) are characterized by particle motion that is perpendicular to the propagation direction: Taken collectively, p- and s-waves are known as “body” waves. The velocities of both can be measured via seismic refraction. Surface Waves, as the name implies, travel primarily along the ground Surface; amplitudes decrease rapidly with depth. There are two types of Surface waves. Like body waves, they are characterized by particle motion. Rayleigh waves are characterized by elliptical motion perpendicular to the Surface: In the near Surface, this motion is “retrograde”, meaning that it is counter-clockwise when the propagation is left-to-right. At depth, the motion can reverse to prograde. Love Waves are created when particles vibrate perpendicular to the propagation direction: While the particle motion is similar to that of shear waves, Love wave amplitude is much higher and decreases rapidly with depth. Love waves are the most destructive waves in earthquakes because of their high amplitude and transverse particle motion. While the various wave types shown above have been isolated for illustration purposes, all are present to some degree whenever seismic energy is traveling through a Solid medium. Hence actual particle motion is extremely complex.

Channel Remapping Channel remapping allows you to change: the Order of channels on each analog spread cable that connects to the Geode reorder the Geode boxes. You would use this option if your cables were wired opposite to the default Order normally used in Geometrics wiring, if you wished to turn your line around to have the low channels at the opposite end, or if your cables had a wiring error. Channel remapping is also often necessary when using more that a single network cable. Default cable wiring of Geometrics seismographs Default Order is defined as the natural electrical Order in which channels are oriented when the system first powers up before remapping. Refer to Section 3 under Connector Wiring that discusses standard wiring configurations. You may have requested a custom wiring configuration from Geometrics. If you are confused about your wiring, contact the factory and refer to the serial number and job number. Geode cables are typically wired in a ‘high-side configuration’, meaning that the Geode connects closest to the highest numbered channel on the analog cable. The 149 figure above shows this configuration for a single box system, with 24 channels. Multiple Geodes The following diagram shows a default single digital line (one network card) system with 3 Geodes. Note that Geode one is always closest to the controller in a default configuration. Multiple Network Lines The next diagram below shows a default configuration with two digital lines (two network cards) with the controller positioned in the middle. Line 1 is on the left and line 2 is on the right. One might use two lines to increase data throughput to reduce time between shots. Like the configuration above, the Geodes are numbered starting closest to the controller. The seismic controller software labels all of the channels contiguously even though they are on two separate digital lines. However, if the lines are collinear, the first line will have the channels Ordered backwards. This can be easily rectified with the remapping feature. There are two ways of remapping channels: automatic mode and manual mode. Automatic mode Settings are listed on the top of the remapping dialog box, and manual mode on the bottom. Automatic Channel Remapping Automatic channel remapping allows you to reverse either the Order of the Geodes on the line, or reverse the Order of the channels on the spread cable. The above diagram shows the result after both channels and Geodes have been reversed, renumbering the line so that low channels start on the left hand side and increase towards the right. In the dialog box, the automatic remapping boxes referencing line 2 remain unchecked, since the default orientation on line two was correct. Manual Channel Remapping Channels can be remapped on an individual basis using the Manual Map Mode. Select the appropriate check box, and enter the Order in which you would like the channels that differs from the default Order. You can specify individual channels separated by a comma (1, 3, 4, 6 etc) or a range of channels (1-13, 24-14 etc). For example, if you wanted the channels Ordered backwards on a 24-channel system, you would enter 24-1. If you wished to reverse the Order of channels 1- 12 in a 24 channel system, you would type 12-1, 13-24. Other examples are shown opposite, and are available by pressing the See Examples button on the remapping menu.

I have attached the instructions that are sent with a new Order acknowledgment. (Installation and Transfer) The license is assigned to a specific Registration ID once fully purchased. This ID can be assigned to a person (we like to know for our own records) if possible but not required and can be transferred to other PC’s as needed. The ID works like a softkey dongle. The software can be active on only one machine at a time. I attached a simplified “Steps with windows_SI Transfer procedure that shows how the software can be moved. The PC must connected to the internet to affect the first part of the transfer (which removes the ID from the PC, making available for the next). Then to place the Reg ID on the next computer is just following the original registration process. Do not lose the ID. Make sure that the ID has been removed before a disc is reimaged or an employee leaves with the PC. If for some reason the Reg ID has to be reset, (computer dies before the ID can be removed) I will require a statement and an end user then for my records. I am available to discuss if needed at the number below 0700-1500 PST. Best, RandL P RiveraCustomer Service Repair Supervisor+1 (408) 428-4254 (direct)+1 (408) 954-0522 (office)support@geometrics.com Attachment : SeisImager_LicenseTransfer_Instructions_v1.2.pdf Attachment : Steps with windows_SI Transfer.pdf Attachment : SeisImager_Installation_Instructions_v7.6.pdf

The time associated with each data point in a SEG-2 data file generated by a Geode is related to the time of the “trigger” event which was instrumental in the production of the file and its content. The Trigger Master and Trigger Distribution The trigger event occurs at the Geode designated within the Controller software as the Trigger Master. Although all Geodes are capable of being Trigger Masters, there must be one and only one Trigger Master in any properly functioning Geode system. The Controller automatically takes care of this requirement when the designation is made by a user, and when the system is established at the time of Controller start-up based on a previous designation (or a default Setting in the case of a “new survey”). All other Geodes in the system will have their Trigger Master circuit disabled. A trigger event can be initiated by an external electrical pulse provided to the trigger input connector of the Trigger Master Geode, or by a command sent via Ethernet from the Controller to the Trigger Master (usually for test purposes), but only when all conditions are satisfied to allow data recording. There is also a special trigger initiation situation, called “self-triggering” which will not be discussed further here. Upon acceptance of a trigger event, the Trigger Master will distribute the trigger signal to all Geodes in the system, itself included, via an RS-485 network that resides within the digital interconnect cabling. (Proper termination of this RS-485 network is automatically taken care of by the Controller.) The trigger signal is propagated through the cabling and Geodes at the nominal speed of 70% of the speed of light, or approximately 2.1x10^8 m/sec. The maximum distance of successful propagation depends on a number of factors such as the number of Geodes involved, the noise environment, the quality of the cables, and the acceptable amount of timing uncertainty for the particular application. Distances approaching or exceeding 1km should be given careful attention in this regard. In a 3-D Geode system involving LTUs, each LTU, unlike a Geode, will reconstruct the trigger signal before sending it on, effectively confining the maximum distance issue to each sub-network separated by LTUs. The penalty is an additional delay of about 100nS for each LTU in the route. The External Trigger Circuit The external trigger input is capacitively coupled, with a 2mS time constant, to the midpoint of a resistive voltage divider. The voltage difference between the two ends of the divider constitute a voltage "window", which size is Set by the trigger sensitivity parameter and can range from essentially zero at the highest sensitivity, to about +/- 2.5V at the lowest sensitivity. The Geode will trigger (if enabled) if and when the coupled signal exceeds the window, in either direction (i.e., positive or negative going). The signal, after the capacitor, is clamped by diodes to the range between the trigger signal ground and +5VDC. The trigger detector output is disabled when the system is disarmed, during a parameter change, and during a shot, up to the trigger hold-off time after the end of the shot. The trigger hold-off time is a parameter Set by the user. Preceding the coupling capacitor (i.e., essentially the node accessible at pin A of the external connector), there is a 3.3K-Ohm pull-up resistor to +5VDC (relative to pin B). Also a fast transient suppressor clamps the input at about +/-14VDC. It is advised that the DC + AC level of any voltage applied to pin A relative to pin B be kept within the range of +/-7V, giving some margin of safety. If a DC voltage somewhat less than +5VDC is applied when the connector is first mated, the instrument may trigger at that moment. But, subsequently, because of the capacitive coupling, it will trigger on the next positive or negative going pulse that exceeds the window level. If the duration of the applied voltage pulse is less than the record length + delay time + hold-off time, then the Geode will effectively be ready to trigger on the same edge of another similar pulse. Sub-sample Synchronization The Geode supports a sub-sample timing synchronization feature used for synchronizing the data acquisition after a trigger event to the distributed trigger signal, so that subsequent time points will be known to within 1/32 (~1/20 at the fastest two sampling rates) sample interval. It does this by increasing the sample interval at the trigger time by 0 to 31/32 of a sample interval in increments of 1/32, so that the first sample after the trigger would represent a time of one sample interval after the trigger event, with a tolerance within 1/32 of a sample interval. The following samples continue from there at the expected intervals. For example, with a selected sampling interval of ¼ mS and a recording delay of 0mS, the first sample in the recorded file for each channel would represent data at 250 to 258uS after the trigger event. This of course potentially introduces a small discontinuity at the time of the trigger, observable depending on the nature of the channel waveform(s). (The zero-phase anti-alias filter will smear the discontinuity into the nearby samples both before and after, consistent with the bandwidth of the filter.) Sub-sample synchronization can be disabled if it is deemed to be detrimental for the particular application, at the expense of losing the 1/32 interval timing accuracy. Timing Errors The principal errors in Geode timing are of two types: those associated with the trigger mechanism and which are static over the duration of the record, and those associated with the time base and which change over the duration of the record. Excluding the trigger propagation delay mentioned above, the trigger timing uncertainty is about 1uS. The known fixed errors have been lumped together and are reported in the SEG-2 file trace headers as channel SKEW. (The actual channel skew is zero, since all channels are effectively sampled simultaneously, but the SKEW value in the header is used as the only place permitting small timing corrections. Note that the SKEW value for every channel is identical.) If the size of this correction is important to the application, the SKEW value should be added to the calculated time points when the data is being processed. The Geode time base has a +/-15ppm stability over temperature (-20C to +70C) and component variations. Thus time drift relative to absolute time and relative to other Geodes is possible. (However, all channels within any Geode enclosure use the same time base, so there is no relative drift between channels in the same enclosure.) Therefore timing uncertainty increases from that existing at the time of the trigger until the time of the next trigger (or end of record). Special Timing Issues Involved with “Continuous” Recording “Continuous” recording is a method that allows unending 100% time coverage with recorded Geode data. It produces a series of time-overlapped records created by the use of a negative time delay Set equal to the record length such that each record consists of completed history at the time of the trigger event. This technique circumvents the problem of data transmission overrunning data acquisition. The principle constraint is that the cycle time from trigger to trigger must always be less than the chosen record length. Otherwise, gaps rather than overlap would result. Commonly it is used with GPSderived triggering in Order to provide time-stamping of each trigger event. Upon consideration of the above, it will become clear that the time-stamp associated with a particular trigger event will pertain to the data in the following record, not to the data in the record in which the time-stamp is written. This comes about because the trigger event ends the record. Because there is data overlap between records, the precise trigger point in the following record at which the time-stamp applies can be found by comparison of the data values at the end of the former record with those near the beginning of the subsequent record. The overlapping data will be exactly identical in both records (since they are read from the same memory location, twice). The earliest data in the subsequent record that goes beyond the data of the previous record is the data that is one sample interval (assuming sub-sample synchronization is enabled) past the time-stamp. Note well that this comparison must be made independently for at least one channel of each 8-channel Geode board Set, because the discrete time at which data values are written to the memory buffer, relative to the trigger event, is a function of each individual board Set in the Geode system. Correct GPS Time-Stamping There are differences between various GPS models that can affect accurate time stamping. The 1PPS signal from a GPS has a “timing edge” and return edge, of which only the former is the true whole-second edge. Some models use a rising edge as the timing edge, some the falling edge, and some have it selectable. Consult the GPS manual to determine the definition of its timing edge. As indicated earlier, the Geode can be triggered on either a rising or falling edge. It is important to insure that the Geode is being triggered on the proper edge in Order to avoid timing that may be a fraction of a second off. This is expanded upon below. Some GPS units provide a very narrow timing pulse, others one that has a nearly 50/50 duty cycle. For the narrow pulse units, almost certainly it is the leading edge (rising or falling) that is the “timing edge”. This case can be easily handled by using the Geode Trigger Hold-off feature. If a 10-second cycle time is desired, Set the Trigger Hold-off time to about 9.5 seconds. In this case, there is a very small chance that the very first trigger could occur on the wrong (trailing) edge, but from then on the leading edge will be used as the triggering edge. If the GPS provides a 50/50 duty cycle edge, and it is not alterable, then the Geode by itself could as easily start on the wrong edge as on the correct timing edge, and continue thusly until restarted. For this case, Geometrics can provide a Trigger Timing Interface Box (TTIB) that will correct the situation. The TTIB can be programmed to respond only to the correct edge (rising or falling), change the polarity if needed, and gate through only one of every N 1PPS pulses, where N is programmable. (The TTIB also incorporates an alarm system that can provide a remote alert if a record is missed.) Another potential issue comes from the variations between GPS models of the time that the serial time string (containing the time value of the associated 1PPS) is issued relative to the 1PPS itself. The Geode Controller attempts to pick the correct serial string based on a calculation involving the known record length, the PC times, and the trigger notification message from the Geodes. But if the GPS issues the serial string at an unusual time (and the time has been seen to vary somewhat with a given GPS unit) then it could pick up the incorrect time, off by 1 second. If rare, it can be subsequently detected and corrected during data processing, but if consistent it may not be easily detected. Again, the TTIB can accommodate the situation by only gating through to the Controller PC the string belonging to the gated-through 1PPS pulse. The Controller Serial Input Time Window can then safely be widened to 2 seconds (assuming the cycle time is more than 2 seconds) if need be, to expand the Controller’s search for the string around the calculated trigger time.

Degaussing is a method by which magnetic domains in metals or magnetic inclusions in other materials are randomized so that net magnetization is minimized. One tool do accomplish this is the “Bulk Tape Eraser” designed to erase data tapes. The method works because the “Bulk Tape Eraser” generates an alternating electromagnetic field, which flips the magnetization of the magnetic domains in the material at 100 or 120 reversals per second (50 or 60 hertz). As the operator slowly removes the “Eraser” from the vicinity of the magnetized material, the magnetic domains of the material individually freeze in one orientation or the other, leaving the domains in a randomized orientation with minimal net magnetic effect. Degaussing with a Bulk Tape Eraser *The procedure is straight forward. Plug the Eraser into an extension cord or wall socket (the Eraser cord is usually short). Holding the object to be degaussed in one hand, depress the Eraser start button and move it towards the object. Once close to the object or section of material, begin moving the Eraser with a small circular motion and then increase the radius of the circle as you draw the Eraser away from the object. DO NOT STOP the Eraser closer than three feet from the object being degaussed or it will become strongly magnetized in one direction! If this happens accidentally, just redo the degaussing procedure over again starting from the beginning. *For larger objects, run the Eraser along tubing or struts in a circular motion to “bathe” the objects in an oscillating field. Be sure to cover the entire Surface area of the object being degaussed. Then slowly withdraw the eraser (while still running) until it is at least 3 feet away. Then release the power switch. *The magnetometer can be used to check the sufficiency of the degaussing procedure. After degaussing, rotate the object close to an operating magnetometer to see if there is a response from the magnetometer. This is best done with a cesium magnetometer operated in gradient mode, but it can be done with a single sensor with one person watching the result and another moving the object near the sensor. Degaussing Sensor Mount Degaussing Pack Frame Degaussing GPS Antenna Limitations of Degaussing with a Bulk Eraser Depth of penetration: The Bulk Tape Eraser can only randomize materials to a certain depth. This is due to the size of the gap in the degaussing unit. A small gap makes for a very large degaussing field at the gap (about 2000 gauss, or 200 million nanoteslas), but also for a very rapid falloff away from the gap. Bulk tape erasers are optimized to penetrate through the thickness of a typical video tape. This gives a typical depth of an inch (2.5 cm). Deeper objects may need to be degaussed using stronger degaussing fields. Degaussing through a conductive chassis: An additional problem occurs when the object being degaussed is covered by a conductive Surface (such as a sheet of aluminum). The degaussing field will generate huge eddy currents in the conductive Surface which will generate its own opposing magnetic field. This will be evident to the operator because the opposing field will cause the degausser to buzz loudly. This doesn’t hurt anything, but be aware that the degaussing field on the other side of the conductive Surface will be attenuated by some amount, so it may take a longer amount of time or multiple passes to degauss the object. The Bulk Tape Eraser is a short duty cycle device. It varies a little from manufacturer to manufacturer, but typically it is rated for 1 minute on and 5 to 10 minutes off. Most have an internal thermal cutout that will shut it off if it overheats, and if tripped may take 20 minutes or more to cool down enough to reset. Frequently Asked Questions Why is degaussing needed? Degaussing misaligns magnetic domains so that there is no net permanent magnetization that would give an offset or heading error to magnetic field readings. Sensitive magnetometers such as those manufactured by Geometrics can be effected by nearby materials that are not sufficiently magnetically randomized. Degaussing does not alter the induced magnetic moment of any material. A piece of steel, when degaussed, is still magnetic because it draws and concentrates the earth’s field through it. However, a degaussed piece of steel is much less magnetic than a permanently magnetized piece. How much effect does it have on magnetic signatures? Depending on the distance from the sensor to the magnetic object and the amount of magnetization, the effects can be very large -10’s of nanoTeslas. Many materials including brass, aluminum, fiberglass and other non-ferrous materials may have some ferrous materials in them naturally or acquired during the manufacturing process. Other materials such as ‘non-magnetic’ stainless steel are hugely magnetic when compared to the sensitivity of our magnetometers. Degaussing can decrease the magnetic effect of these materials by a factor of 10 or more. What should I degauss? The operator should degauss any metallic object that is near the sensor. By “near”, in general we mean within 1 meter but certainly those metallic and non-metallic materials within a few centimeters of the sensor must be considered (this also includes the sensor itself, which could have minute magnetic inclusions in the sensor materials). This could also include GPS antennas, magnetometer cart assemblies (including brass fittings, bolts, clamps), buckles, eyeglasses, boots and parts of backpacks. We would also do occasional degaussing of the G-858 console and batteries. Will degaussing hurt anything? This is a tough question since it is impossible to imagine every conceivable system arrangement that could be subjected to degaussing. In all our experience we have never had any electronics device hurt by the degaussing process. This is because the induced voltages from the degausser are low, and the electronics components have a fairly high impedance at low voltages. It would be safer to degauss electronics while the power to the electronics is turned off in case the small induced voltages cause the device to operate incorrectly. It is always safe to degauss any of Geometrics’ manufactured equipment (including the sensor). On the other hand, here are some things to consider when degaussing some types of objects. Large conductive planes or rings will have large circulating currents induced in them by the degausser (but the voltages are still very small). This induced current will produce an opposing magnetic field that will fight the degaussing field – causing both the degausser and the conductive plane/loop to vibrate substantially. If the device being degaussed is sensitive to this vibration (intricate mechanical workings and the like) then this is a possible route for causing some damage. Also, sometimes objects being degaussed have embedded magnets that are necessary for the device to operate properly. A good example is a device with a permanent magnet speaker inside. Generally it is hard to degauss a magnetically hard permanent magnet, but the degausser is strong enough to at least partially do the job. A partially degaussed speaker (or other object that requires a magnet to work right) isn’t going to work the same as before – so be aware. [Things that have magnets in them shouldn’t be used near magnetometers anyway.] When to degauss and how often? We recommend that parts close to the sensor be degaussed before every major survey event. In other words on a weekly or monthly basis or before a new survey. Remnant magnetism or “Perm” can be “picked up” (domains realigned) when the materials are static in the earth’s magnetic field for a period of time. The amount of time required to acquire a “Perm” can be from days to weeks or months depending on the magnetic “hardness” of the materials. This is also known as the materials “susceptibility”, that is, susceptibility to being magnetized. Also, magnets are everywhere, and they can easily and unknowingly ‘perm’ up parts on or near the sensor. Magnetic screwdrivers, for example, are great for holding steel screws on the end of the driver while starting them into a threaded hole, but they are bad news near any magnetometer sensors.

Altitude refers to Meters Above Mean Sea Level. For both MagArrow I and II, the altitude is ellipsoidal and the earth model is WGS84. For additional information: Overview Reported elevations from MagArrow (and G-864 and MagEx) are the unedited values from the elevation field in the GNSS's GGA NMEA string. That value is the GNSS's calculated height above geoid; height above geoid is the standard meaning of the elevation field in the GGA NMEA string. But what does calculated height above geoid mean? Definitions GNSS - Global Navigation Satellite System GPS - The GNSS operated by the United States. Other systems include GLONASS(Russia), Galileo (Europe), BeiDou (China), QZSS (Japan), IRNSS (India). Ellipsoid - A comparatively simple or abstract geometric model of Earth's Surface. Geoid - A more complex model of Earth's Surface that takes the place of what was previously called Mean Sea Level. At any particular latitude or longitude, the geoid's Surface may be above or below the ellipsoid's by as much as a few hundred meters, depending on regional and local geography and geology. Reference datum - A specific model of Earth's shape (such as WGS84, EGM96...), including references to specific landmarks. Calculations A particular GNSS, for example the GPS system run by the United States, provides timing data to a receiver to calculate the receiver's position above or below a particular latitude and longitude on the Surface of the ellipsoid. The GNSS receiver first uses that timing data to calculate its height over the ellipsoid, and then subtracts from it the local height of the geoid over the ellipsoid (or HAE), to arrive at the local height of the receiver over the geoid (or in old-fashioned terms, elevation over mean sea level): h - calculated height above geoid. This is the value reported in the GGA elevation field. H - height of the receiver over the ellipsoid (calculated from GNSS timing signals) N - local height of geoid over the ellipsoid, or HAE, per a lookup table or other local reference. h = H - N      Because the local height of the geoid over the ellipsoid is not provided by the GNSS, it must be provided locally, i.e. by the GNSS receiver, which may contain an internal database from which the local geoid height over ellipsoid (or HAE) can be found, based on the receiver's latitude and longitude. Small GNSS receivers contain small HAE databases, so the HAE value will not be exact. Some small receivers contain no HAE table at all; in this case HAE is deemed to be zero, so that the reported elevation is the uncorrected height over ellipsoid.​​​​​​​ A user of elevation data from Geometrics' MagArrow, G-864, and MagEx magnetometers may evaluate or adjust the reported values of the GGA elevation field and the GGA HAE field, by comparing the GGA HAE values to another source of local HAE data; this may particularly be useful for GNSSes that report a HAE equal to zero. Geometrics magnetometers do not currently record the values of a VDOP calculation, which offers an additional statistical estimate of the accuracy of the GNSS elevation measurement.

Further Elaboration: You might ask this question to try and understand the low frequency response to determine if the Geode amplifiers effectively have a flat response from DC up. Does the Geode go down to DC for example? Answer: We apply anti-alias filters to the data to prevent out of band noise from being introduced into the data. The filters are Set with a corner frequency at ¾ of the Nyquist frequency (1/2 the sampling frequency) for almost all of the sampling frequencies. When we sample at 1.5625 uS, the Nyquist frequency is 32kHz and the filters are Set at 20 kHz, because of limitations of our electronics. There are two single-pole filters: one analog and one digital. The analog filter is a simple RC filter with 1uF +/-5% and 100kOhm +/- 1%. We short out the capacitor in the conversion process. The digital filter is software controlled when the option is registered, so it can be switched in or out in the field. It is an IIR Butterworth with a -3dB corner at 0.9Hz for 48ksps sampling, and 0.6Hz at all the lower sample rates. Also, we offer software and hardware options to modify the low end frequency response of the Geode. Low-end bandwidth modification: 1.5 Hz, P/N 28311-37 0.6 Hz, P/N 28147-01 DC, P/Ns 28147-02, 28311-37per system plus

MFAM-SuperMag (LCS100S) or MFAM-SX (LCS100X) can be configured to achieve dead-zone-free operation, in which the combined sensor is always active no matter where in the world and which direction the device is oriented. To Set up the dead-zone-free configuration: Make sure the MFAM is in the "One Sensor (No Dead Zone) run mode. If not, please refer to "How to switch the operating mode for SuperMag MFAM" on our website found here: How to switch the operating mode for SuperMag (LCS100S) MFAM?. Orient two sensors orthogonally. The ideal relative orientation is shown below (also in the test report in the USB drive shipped with the unit). This configuration works for both the "Low Heading Error" and the "Low Noise" modes. Low Heading Error Only mode If you only wish to run the sensor in the "Low Heading Error" mode (note that SX MFAM does NOT have the "Low Noise" mode), a simpler configuration, as shown below, can also achieve the dead-zone-free operation.

Below is a series of diagrams that can act as analogies for impacts. If the impulse is enacted rigidly (hard tip hammer, steel plate, etc.), the impulse will look something like the far-left figure. High-amplitude (height of the curve), narrow wavelength (width of the curve). This is because the impacted materials respond rigidly to the impulse, i.e. the hammer rebounds from the plate almost instantaneously. Therefore, as a result of the narrow-wavelength impulse, the transmitted waves will have relatively high-frequency (short wavelength) content. As you use softer and softer impact materials, applying impulses of equal force will appear like the diagrams to the right (smaller amplitude, longer wavelength). The impacted materials are responding less-rigidly to the impulse, so the hammer spends more time on the plate due to the more absorptive nature of the impact. The same amount of energy has been put in (area under the curve), but the amplitude of the input (height of the curve) decreases to compensate for the input duration (width of the curve) caused by the impact absorption of the softer materials. Therefore, as a result of the wide-wavelength impulse, the transmitted waves will have relatively low-frequency (long wavelength) content. Using a more rigid striker plate (like one made of aluminum) on a hard Surface can cause the generated wave frequency to be too high at times given the survey goals, so we suggest using a polyethylene plate on a relatively Solid material like asphalt. Remember: lower frequency -> deeper signal penetration -> decreased signal resolution.

Overview The MagEx instrument and the MagNav app both display information about the state of the instrument's battery. Battery state and reporting exist in bands according to percentage of remaining battery capacity: 30% or higher:The instrument has good remaining capacity.The LED on the instrument's power switch glows a Solid green.MagNav displays the battery percentage or voltage in black text on a white background. Between 20% and 30%:The instrument has capacity to survey for additional time, but if you will be surveying a significant amount more, start thinking about changing the battery.The LED on the power switch is blue.MagNav displays the battery percentage with a blue background. Between 5% and 20%:You can continue to survey, but the battery is running low and you should consider changing the battery soon.The LED on the power switch is red.MagNav displays the battery percentage with a red background, and periodically notifies you that the battery is running low. Below 5%:The battery is running low, and the instrument may turn off at any time in Order to preserve battery health. You should change the battery as soon as possible. Temperature-related effects:Battery performance also changes as the temperature of the battery changes; as the temperature of a battery falls, the voltage it supplies also decreases, and the total energysupplied by the battery decreases. This means that in cold weather a battery will not last as long as in hot weather. The battery percentages reported in the instrument are adjusted for the effect of temperature; at a given battery voltage a cold battery will display a higher percentage than a warm battery will report. The effects of colder temperatures are not normally permanent; as a battery warms up, its output voltage and energy return to higher levels. Notes about the calculation:The MagEx instrument includes 2 batteries, and each battery includes 3 separate cells. Battery percentages are calculated from only one battery in the instrument - either the single battery if only one is connected, or from the better battery if two batteries are connected. Reported battery percentage is an estimate, based on measurements of the behavior of healthy batteries in instruments in the field and in the lab. Battery performance may change as a battery ages and as the temperature changes. The best practice for batteries is to use 2 healthy, fully charged batteries, and replace them both when the percentage falls below 20%.

There are basically three types of "gold": low concentration disseminated gold in ore, placer gold deposits and Solid gold such as that associated with treasure. Magnetometers are used to find disseminated gold by its association with mineralized zones which also contain magnetite or other magnetic minerals. Magnetometers are often used in conjunction with airborne electromagnetic surveys to find the conductive ore bodies. Placer gold is the type found in buried stream channels such as the gold which sparked the California gold-rush in 1849. Gold dust and magnetic minerals have been concentrated in river banks over thousands of years. Where there is gold there is often magnetite and therefore the magnetometer can be used to locate placer gold deposits. Gold treasure is a different story and being non-magnetic gold, silver, and other precious minerals are not directly detectable by the magnetometer. The magnetometer can only detect ferrous (iron or steel) objects. If the gold is stored in an iron box or has iron materials next to the gold (such as colonial ship ballast stones in the marine environment), there is the possibility of detecting the iron material. This is true for land and marine (sunken galleon) gold bullion. The vast majority of target search surveys are performed on a grid in a "lawn mower" back and forth manner to cover the area of interest. Lane spacing is dependent on target size (magnetic mass). At a sensor to target distance of 2 to 3 meters there will need to be at least 1-2 kilograms of iron. This can produce a 1-2 nT anomaly that is detectable in a magnetically clean environment. The ideal environment would be in a plowed farm field or the bottom of the ocean away from human activity i.e., away from a port or harbor. You will probably not be able to detect this small of an anomaly in a city or port location. The more iron mass there is, the better the chance of detecting it. Training to use the magnetometer can take 1-2 days depending on experience with Setting up computerized survey equipment and a GPS. Processing the magnetic data requires several days of training and would require a geophysical background to interpret the final maps. We provide free software to make maps and estimate the target depth of burial (inversion). If you are unfamiliar with this procedure, we would recommend that you find a local geotechnical firm to look at the data to determine if there are anomalies that should be investigated further. Remembering that non-ferrous materials do not cause anomalies (gold, silver, copper, brass, aluminum, gems) you will be looking for anomalies either associated with the container OR associated with ground disturbance (i.e., gravesite). In this way some anomalies can be detected where there has been an excavation such as a gravesite. In Order to understand the process more fully, we strongly suggest that you download and read the Applications Manual for Portable Magnetometers. Other additional resources are available. Understanding how the magnetometer functions and how the earth’s field responds to distortions due to ferrous materials will help you make good decisions about how to interpret and use the data to direct recovery or exploration efforts.

Hi All,   We are using the Teensy 4.1 as a logger (Adafruit GPS is linked with the Teensy) for the MFAM SX. Below is the code for the Arduino IDE (Teensy), for people who might find it useful, Roi   #include <NativeEthernet.h> #include <SD.h> // ---- NETWORK CONFIGURATION ---- byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; IPAddress ip(192, 168, 2, 10); IPAddress mfamIP(192, 168, 2, 2); uint16_t mfamPort = 1000; EthernetClient client; // ---- PACKET STRUCTURE ---- const int PACKET_SIZE = 1380; const int SAMPLE_SIZE = 32; const int HEADER_SIZE = 16; const int NUM_SAMPLES = 40; const int SD_CHIP_SELECT = BUILTIN_SDCARD; uint8_t buffer[PACKET_SIZE]; int bufferPos = 0; // ---- SD CARD ---- File logFile; bool sdReady = false; unsigned long sampleCount = 0; unsigned long fileStartTime = 0; char filename[32]; // ---- AUXILIARY CHANNEL STORAGE ---- double gyroX = 0, gyroY = 0, gyroZ = 0, gyroT = 0; double accelX = 0, accelY = 0, accelZ = 0, accelT = 0; double compassX = 0, compassY = 0, compassZ = 0, compassT = 0; // ---- GPS FROM ADAFRUIT MODULE ON SERIAL1 (Pin 0 = RX) ---- char gpsBuffer[256]; int gpsBufferPos = 0; char gpsString[128] = ""; char gpsDate[12] = "00/00/00"; char gpsTime[16] = "00:00:00.000"; bool gpsFix = false; uint8_t tsStatus = 0; // ---- OUTPUT CONTROL ---- // Set to 1 to log every sample, 10 for 100Hz, 20 for 50Hz, etc. const int DOWNSAMPLE_FACTOR = 1; // 50 Hz output int downsampleCounter = 0; // How many minutes per file. Set to 10, 20, 60, etc. const int FILE_MINUTES = 10; // ---- LED INDICATOR ---- // Off = starting up // Very slow blink (every 3 sec) = connected and logging // Fast blink (4/sec) = connected but no data arriving // Solid on = no SD card // 3 quick flashes then pause = cannot connect to MFAM const int LED_PIN = 13; unsigned long lastBlinkTime = 0; bool ledState = false; unsigned long lastDataTime = 0; // ---- FUNCTION PROTOTYPES ---- void createNewFile(); void parsePacket(uint8_t* pkt); void parseAuxChannels(uint8_t* sample, uint16_t frameID); void readGPS(); void parseGPRMC(char* sentence); void writeSample(unsigned long timestamp, uint16_t fiducial, double mag1, uint16_t mag1s, double mag2, uint16_t mag2s, uint16_t sysStatus); int16_t toSigned16(uint16_t val); void createNewFile() { static int fileNumber = 0; // On first call, find the next available file number if (fileNumber == 0) { char testName[32]; for (int i = 1; i <= 99999; i++) { snprintf(testName, sizeof(testName), "MFAM_%05d.txt", i); if (!SD.exists(testName)) { fileNumber = i - 1; // Will be incremented below break; } } } fileNumber++; snprintf(filename, sizeof(filename), "MFAM_%05d.txt", fileNumber); logFile = SD.open(filename, FILE_WRITE); if (logFile) { logFile.println("Mag 1,Mag 2,Fid,SysS,Mg1S,Mg2S,Gyro X,Gyro Y,Gyro Z,Gyro T,Accel X,Accel Y,Accel Z,Accel T,CompassX,CompassY,CompassZ,Comp T,Date,Time,TS Status,GPS"); logFile.flush(); fileStartTime = millis(); Serial.print("Logging to: "); Serial.println(filename); } else { Serial.print("ERROR: Could not create "); Serial.println(filename); } } void Setup() { Serial.begin(115200); delay(2000); // Start GPS serial port (Adafruit Ultimate GPS defaults to 9600 baud) Serial1.begin(9600); pinMode(LED_PIN, OUTPUT); digitalWrite(LED_PIN, LOW); memset(gpsString, 0, sizeof(gpsString)); // Initialize SD card if (SD.begin(SD_CHIP_SELECT)) { sdReady = true; Serial.println("SD card ready."); } else { Serial.println("WARNING: No SD card found. Serial output only."); digitalWrite(LED_PIN, HIGH); } // Initialize Ethernet Ethernet.begin(mac, ip); if (Ethernet.hardwareStatus() == EthernetNoHardware) { Serial.println("ERROR: No Ethernet hardware found!"); while (true) {} } Serial.print("Teensy IP: "); Serial.println(Ethernet.localIP()); Serial.print("Connecting to MFAM at "); Serial.print(mfamIP); Serial.print(":"); Serial.println(mfamPort); if (client.connect(mfamIP, mfamPort)) { Serial.println("Connected to MFAM!"); } else { Serial.println("Connection failed!"); } Serial.println("Waiting for GPS fix..."); if (sdReady) { createNewFile(); } Serial.println("Mag 1,Mag 2,Fid,SysS,Mg1S,Mg2S,Gyro X,Gyro Y,Gyro Z,Gyro T,Accel X,Accel Y,Accel Z,Accel T,CompassX,CompassY,CompassZ,Comp T,Date,Time,TS Status,GPS"); } void loop() { // Always read GPS data from Serial1 readGPS(); if (!client.connected()) { Serial.println("Disconnected. Reconnecting..."); if (sdReady && logFile) { logFile.flush(); } for (int i = 0; i < 3; i++) { digitalWrite(LED_PIN, HIGH); delay(100); digitalWrite(LED_PIN, LOW); delay(100); } delay(1400); client.connect(mfamIP, mfamPort); if (client.connected()) { lastDataTime = millis(); } return; } while (client.available()) { buffer[bufferPos] = client.read(); bufferPos++; if (bufferPos >= PACKET_SIZE) { parsePacket(buffer); bufferPos = 0; lastDataTime = millis(); } } // LED patterns if (sdReady) { if (millis() - lastDataTime > 3000) { if (millis() - lastBlinkTime > 125) { ledState = !ledState; digitalWrite(LED_PIN, ledState ? HIGH : LOW); lastBlinkTime = millis(); } } else { if (millis() - lastBlinkTime > 1500) { ledState = !ledState; digitalWrite(LED_PIN, ledState ? HIGH : LOW); lastBlinkTime = millis(); } } } // New file every FILE_MINUTES minutes if (sdReady && logFile && (millis() - fileStartTime > (unsigned long)FILE_MINUTES * 60UL * 1000UL)) { logFile.close(); createNewFile(); } } // ---- GPS READING FROM ADAFRUIT MODULE ON SERIAL1 ---- void readGPS() { while (Serial1.available()) { char c = Serial1.read(); if (c == '$') { gpsBufferPos = 0; } if (gpsBufferPos < (int)sizeof(gpsBuffer) - 1) { gpsBuffer[gpsBufferPos] = c; gpsBufferPos++; } if (c == '\n' || c == '\r') { gpsBuffer[gpsBufferPos] = '\0'; if (strncmp(gpsBuffer, "$GPRMC", 6) == 0 || strncmp(gpsBuffer, "$GNRMC", 6) == 0) { // Save full sentence for logging strncpy(gpsString, gpsBuffer, sizeof(gpsString) - 1); gpsString[sizeof(gpsString) - 1] = '\0'; // Remove trailing newline/carriage return int slen = strlen(gpsString); while (slen > 0 && (gpsString[slen - 1] == '\n' || gpsString[slen - 1] == '\r')) { gpsString[slen - 1] = '\0'; slen--; } parseGPRMC(gpsBuffer); } gpsBufferPos = 0; } } } void parseGPRMC(char* sentence) { // $GPRMC,HHMMSS.sss,A,lat,N,lon,W,speed,course,DDMMYY,... char copy[256]; strncpy(copy, sentence, sizeof(copy) - 1); copy[sizeof(copy) - 1] = '\0'; char* token = strtok(copy, ","); int field = 0; while (token != NULL && field < 10) { switch (field) { case 1: // Time if (strlen(token) >= 6) { snprintf(gpsTime, sizeof(gpsTime), "%c%c:%c%c:%s", token[0], token[1], token[2], token[3], token + 4); } break; case 2: // Fix status gpsFix = (token[0] == 'A'); break; case 9: // Date if (strlen(token) >= 6) { snprintf(gpsDate, sizeof(gpsDate), "%c%c/%c%c/%c%c", token[0], token[1], token[2], token[3], token[4], token[5]); } break; } token = strtok(NULL, ","); field++; } // Update GPS bits of tsStatus tsStatus = (tsStatus & 0x0C); // Keep MFAM PPS bits (3,2) tsStatus |= 0x01; // Bit 0: RMC sentence received if (gpsFix) { tsStatus |= 0x02; // Bit 1: GPS fix valid } } // ---- MFAM DATA PARSING ---- int16_t toSigned16(uint16_t val) { if (val > 32767) return (int16_t)(val - 65536); return (int16_t)val; } void parseAuxChannels(uint8_t* sample, uint16_t frameID) { uint8_t auxID = (frameID >> 11) & 0x07; uint16_t aux0 = sample[16] | (sample[17] << 8); uint16_t aux1 = sample[18] | (sample[19] << 8); uint16_t aux2 = sample[20] | (sample[21] << 8); uint16_t aux3 = sample[22] | (sample[23] << 8); switch (auxID) { case 1: compassX = toSigned16(aux0) / 0.01333333; compassY = toSigned16(aux1) / 0.01333333; compassZ = toSigned16(aux2) / 0.01333333; compassT = toSigned16(aux3) / 128.0 + 25.0; break; case 2: gyroX = toSigned16(aux0) / 16.384; gyroY = toSigned16(aux1) / 16.384; gyroZ = toSigned16(aux2) / 16.384; gyroT = toSigned16(aux3) / 512.0 + 23.0; break; case 4: accelX = toSigned16(aux0) / 16384.0; accelY = toSigned16(aux1) / 16384.0; accelZ = toSigned16(aux2) / 16384.0; accelT = toSigned16(aux3) / 512.0 + 23.0; break; default: break; } } void writeSample(unsigned long timestamp, uint16_t fiducial, double mag1, uint16_t mag1s, double mag2, uint16_t mag2s, uint16_t sysStatus) { char tsStr[12]; snprintf(tsStr, sizeof(tsStr), "%d%d%d%d%d%d%d%d", (tsStatus >> 7) & 1, (tsStatus >> 6) & 1, (tsStatus >> 5) & 1, (tsStatus >> 4) & 1, (tsStatus >> 3) & 1, (tsStatus >> 2) & 1, (tsStatus >> 1) & 1, tsStatus & 1); char sysHex[8], m1sHex[8], m2sHex[8]; snprintf(sysHex, sizeof(sysHex), "%04X", sysStatus); snprintf(m1sHex, sizeof(m1sHex), "%04X", mag1s); snprintf(m2sHex, sizeof(m2sHex), "%04X", mag2s); char line[512]; snprintf(line, sizeof(line), "%10.4f,%10.4f,%4d,%s,%s,%s,%10.2f,%10.2f,%10.2f,%5.1f,%8.5f,%8.5f,%8.5f,%5.1f,%8.1f,%8.1f,%8.1f,%5.1f,%s,%s,%s,%s", mag1, mag2, fiducial, sysHex, m1sHex, m2sHex, gyroX, gyroY, gyroZ, gyroT, accelX, accelY, accelZ, accelT, compassX, compassY, compassZ, compassT, gpsDate, gpsTime, tsStr, gpsString); if (sdReady && logFile) { logFile.println(line); if (sampleCount % 1000 == 0) { logFile.flush(); } } if (sampleCount % 500 == 0) { Serial.println(line); } } void parsePacket(uint8_t* pkt) { // Get PPS bits from MFAM system status uint16_t firstSysStatus = pkt[HEADER_SIZE + 2] | (pkt[HEADER_SIZE + 3] << 8); uint8_t mfamPPSbits = (firstSysStatus >> 12) & 0x0C; tsStatus = (tsStatus & 0x03) | mfamPPSbits; for (int i = 0; i < NUM_SAMPLES; i++) { int offset = HEADER_SIZE + (i * SAMPLE_SIZE); uint16_t frameID = pkt[offset] | (pkt[offset + 1] << 8); uint16_t fiducial = frameID & 0x07FF; uint16_t sysStatus = pkt[offset + 2] | (pkt[offset + 3] << 8); uint32_t mag1raw = pkt[offset + 4] | (pkt[offset + 5] << 8) | ((uint32_t)pkt[offset + 6] << 16) | ((uint32_t)pkt[offset + 7] << 24); double mag1 = mag1raw * 0.05 / 1000.0; uint16_t mag1status = pkt[offset + 8] | (pkt[offset + 9] << 8); uint32_t mag2raw = pkt[offset + 10] | (pkt[offset + 11] << 8) | ((uint32_t)pkt[offset + 12] << 16) | ((uint32_t)pkt[offset + 13] << 24); double mag2 = mag2raw * 0.05 / 1000.0; uint16_t mag2status = pkt[offset + 14] | (pkt[offset + 15] << 8); parseAuxChannels(pkt + offset, frameID); sampleCount++; downsampleCounter++; if (downsampleCounter >= DOWNSAMPLE_FACTOR) { downsampleCounter = 0; writeSample(millis(), fiducial, mag1, mag1status, mag2, mag2status, sysStatus); } } }

If you purchase a low-noise MagArrow (I or II), the factory default is the low-noise mode. You can also look up the current running mode by loading the following website (in Instrument Status) after connecting to the MagArrow: 192.168.1.1/systemtest.cgi To switch to a different mode, please download the special software below and follow the instructions in the readme file: Attachment : SwitchModes.zip Please note that even in the low-noise mode, the heading effect is typically only ~20% worse than that in the low-heading mode. For most applications, you don't need to switch to the low-heading mode.

You can 3D print a dead-zone-free sensor holder from the attached .step file. Attachment : Sensor Holder Perm Shell_Thin Wall_v10.zip

To Set the time on a MetalMapperII Panasonic Toughpad tablet: 1) Using the Applications menu, open a terminal window 2) Set the date and time you want, using the following example as a guide: sudo date -s "2024-02-20 03:25:55 PM PDT" You may need to enter the sudo password (which is the same as the password for the standard "geometrics" user. 3) To change the timezone, use the terminal window to get a list of timezones: ls /usr/share/zoneinfo // To drill into a region, expand the command as follows: ls /usr/share/zoneinfo/Pacific Set the local timezone using this command: // Open the timezone file to edit it. You may need to enter your user password sudo mousepad /etc/timezone // Type in the timezone name, of the timezone you want to use, on a single line in the file, for example like this: Pacific/Guam If you want to see your time in UTC, Set the timezone to "Etc/UTC". If you want to Set the time in UTC, then when you Set the time using the "date" command, use UTC as follows: sudo date -s "2024-02-20 03:25:55 PM UTC"