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Surveying using a randomized impulsive source (called "mini-Sosie), such as a Wacker, is supported by the StrataVisor NZ and the Geode along with the Urban Seismic software and hardware package. Read our Random Source Seismic Surveying Manual
In general, Mini-Sosie surveying is useful in noisy, urban environments, particularly in close proximity to roads where near-field noise suppression can be used effectively.
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.
Stacking is a complicated topic, and warrants its own technical note. Which stacking features are available and how they work depends which modes you are in. There are three main mode “groups”: SAVE, CORRELATION, AND STACK. Within those are sub modes whose names indicate their function.
Save
Autosave
Manual Save
Correlation
No correlation
Standard correlation
Stack before Correlation
Stack after Correlation
Random Source Correlation
Stack
Autostack
Replace
There is a complicated interplay between the above modes and between these modes and the stack options:
Stack polarity Display Intermediate Stacks
Unstack Delay
We will examine each possible combination in rough order of popularity
Modes: Manual save , No correlation, Autostack
This is the most common configuration used in refraction and downhole surveys.
Each shot is automatically stacked
Each stacked record is Displayed as the stack count increments
The stack count continues to increment with each shot until you clear the data, even if you save the data sometime in the process.
Stack Polarity can be changed at any time. This is most often used in shear wave surveys where reverse-polarity stacking is required.
Unstack Delay gives you the option to unstack the most recent stack; for example, setting the stack count from 4 back to 3. The data will be held in a temporary buffer for n seconds, during which time you can choose whether to stack or not. If you do nothing, the data will be automatically stacked after n seconds, and unstacking will be no longer be an option for that stack. If Unstack Delay is set to zero, this feature is Disabled.
Modes: Auto Save, No correlation, Autostack
This is the most common configuration used in impulsive reflection surveys.
Each shot is automatically stacked until the Stack ulmit is reached.
When the Stack ulmit is reached, the data are saved automatically.
Data are automatically cleared and the stack count is reset to one the next time the seismograph triggers after saving the data.
Stack Polarity is generally left set to Positive. Displaying intermediate stacks is optional. Disabulng this option results in faster production, since the data do not need to be sent over the network with every stack.
Modes: Auto Save, Standard Correlation, Stack Before Correlation
This is the most common configuration used in swept-source reflection surveys.
Each shot is automatically stacked until the Stack ulmit is reached.
When the Stack ulmit is reached, the data are saved automatically.
Data are automatically cleared and the stack count is reset to one the next time the seismograph triggers after saving the data.
Data are stacked in raw, uncorrelated form in the Geodes, and are not sent to the PC until the Stack ulmit is reached.
When the Stack ulmit is reached, the stacked raw record is correlated in the Geode (with the most recent pilot), sent to the PC, and saved.
Modes: Auto Save, Standard Correlation, Stack After Correlation
This is the most common configuration used in Random Source (mini-Sosie) reflection surveys.
Each shot is automatically stacked until the Stack ulmit is reached.
When the Stack ulmit is reached, the data are saved automatically.
Data are automatically cleared and the stack count is reset to one the next time the seismograph triggers after saving the data.
Each individual record is correlated with its own pilot and stacked in correlated form in the Geodes. Displaying intermediate, correlated stacks is optional.
When the Stack ulmit is reached, the stacked, correlated record is sent to the PC and saved.
Modes: Auto Save, Replace
This is the most common configuration used in Continuous Recording surveys.
Each stack is replaced by the previous. If Auto Save is not enabled, the previous stack is lost.
If Auto Save is on the Stack ulmit is hard-coded to 1.
Each shot is Displayed.
I was doing a survey, and the tablet lost connection with the sensor, with no data being saved to the tablet. So I took the SD card of the sensor Box, hoping that the data was kept there at least as a backup before the survey ended and data was completely transferred to the tablet. But there is nothing on the SD card. It is empty instead of having a LOST.DIR folder that is also empty.So, my question is, what is the sensor Box SD card for?Second, is there a way to prevent tablet Disconnection from the sensor WIFI (which happens frequently) and backup data when this happens?
Geodes do have an option to have a factory installed oscillator board at extra cost that is used to test the electronics in the Geode. These are not normally installed for most of our users.
Users do have the option to run geophone tests using the standard equipped Geode Seismograph that can run line continuity and geophone tests. This can be accessed from the system->tests->Run Geophone/Line tests.
Oscillator boards are typically installed during purchase. Fewer than 5% of the customers purchase that option, that level of QC is typically not necessary. For more information please read the test Box manual. We no longer supply the Test Box to external customers.
A description of how to run the tests if you use the test Box or if you use the internal oscillators is described in Section 2.11.3.1 RUN INSTRUMENT TESTS (OPTIONAL ADD-ON FEATURE) of the manual. The latest standard Geode Operations Manual has more information.
You can run the tests outlined in the Geode Operations Manual to detect the bad geophones and spread cables.
If you require a calibration certificate for your Geode please consult our Support Note.
All Geophysical surveys require interpretation given limited understanding of the site, data from equipment, and ground truthing. Any interpretation provided is the best that can be provided according to the geophysical expertise and experience of the geophysicist.
Thank you.
No, I am asking about the micro SD card on the Box board.
The cables between the sensors and the MFAM module are flexible circuit boards, and the length is limited to 20 inches.
It is possible to remove the MFAM module from the Development kit Box and then reconnect it using a ribbon cable. That would allow you to extend the MFAM module and sensors away from the Dev Kit Box. Our engineers have tested it to 4 meters.
Below are some details about the ribbon cable.
The connector on the MFAM unit is Samtec FSH-110-04-F-DH. Its mating connector is Samtec SFMH-110-02-L-D-WT.
The easiest option for an extender cable between the MFAM and the Dev Kit is a pair of cable assemblies from Samtec www.samtec.com which has male/female mass terminate connectors put onto a ribbon cable. These connectors plug Directly into the MFAM I/O connector and also into the Development Kit. We are comfortable with lengths to 10 feet total. The samtec P/N for this cable is: FFMD-10-T-60.00-01-F-N
The ‘60.00’ number specifies the cable length in inches (which equals 5 feet). We have found that there is generally a 2-4 week lead, time since they are made to order and not an off-the-shelf part.
(There is another solution as well if you want to make adapter boards at each end (Dev Kit and MFAM). The exact Samtec mates for the MFAM / Dev Kit connectors are made in PCB mount connectors only, so if you make simple small adapter board to adapt the samtec connector to another connector of your choice. We've done this with ExpressPCB which is fast and inexpensive. A board set from ExpressPCB is about $70 including shipping. Our Engineering Team has a design and parts list they can send you if you're interested in going this route.)
General information
The most common symptoms of intermittent connection issues are shown below: D_CY shows a background decay signal is either much higher than normal, and/or C_CY is a flat line (doesn’t decay).
Figure 1 Intermittent connection issue.
Where is the failure occurring?
The two most common places where intermittent issues occur are at the two ends of the Rx cable: the joint between the Rx cable and the Cart and the joint between the Rx cable and the EDA Box (orange Box).
Now we need to identify which joint has the intermittent issue.
Set up the MM2x2 in DAM mode.
Collect DAM data while keeping the Cart stationary but tapping one joint.
Collect another DAM data while tapping the other joint.
Analyze the DAM data by plotting the “Monostatic_5” for all 12 Rx channels in Geosoft. The channels having intermittent issues will appear much noisier.
If you have MatLab software, you can download the MatLab code to analyze the DAM data. Example plots are shown below. It is obvious that “ZA” channel has the intermittent issue in Figure 2 and “XB” channel is open in Figure 3 (very flat line, no noise at all). Click here to download the code:
Attachment : Intermittent_noise_full.zip
.
If both DAM and IVS data have the same problematic channel(s), we are confident that the intermittent issues observed in IVS data are repeated in DAM data, and by tapping at that location, we are able to identify the intermittent joint.
Figure 2 Intermittent "ZA" channel.
Figure 3 Open "XB" channel.
What to do next? Disconnect the problematic joint and clean the connectors on both sides thoroughly (using an acid brush and a can of compressed air). Reconnect and try the tapping method again. If the problem goes away (no more noisy channels), the intermittent issue is likely caused by dust.
If cleaning doesn’t fix the problem, swap out the Rx cable and repeat the tapping method. If the problem goes away, it is likely caused by a bad Rx cable.
If there is another set of EDA and Cart available, swap out the EDA and the Cart to identify the problematic part.
If not, use the tapping location to identify the problematic part.
Fill out the RMA form at .
If it is the Cart, send in the whole system for inspection/repair. You can contact Geometrics for MM2x2 rental if you need to continue your work during the down time.
If it is the EDA, we recommend sending in the EDA only. It will save your repair time since it is much faster to unpack/pack/ship the EDA than the whole system. You can contact Geometrics for EDA rental if you need to continue your work during the down time.
Warning
Please note that this tapping method should ONLY be tried when intermittent issues have been observed in IVS tests. It is NOT recommended to use it as a daily QC test because it does put extra stress on connectors and likely leads to a shortened connector lifetime if applied too often.
@aldsantos I see. Please try it anyway next time in the field. Let us know if loss of connection still occurs after you have selected to stay connected to the G-864 WIFI. Thanks!
@aldsantos For the current version of the embedded software, some raw data was first stored in the microSD and then transferred to the tablet. Data logging stops once the WIFI connection is lost. In the future, if we have an easier way to access the microSD, we may use it as a backup.
Regarding the loss of connection, I was in the middle of the field, far away from internet/WIFI connection. Indeed, it stopped collecting data.
Regarding your SD card question, you must mean the USB drive, right? The drive is not for storing mag data but for running the embedded software.
The reason why the tablet lost connection with the sensor is because the G-864 WIFI has no internet access. The tablet will try to switch to another WIFI with internet access and Disconnect from the G-864. To prevent this from happening, in the warning window of the tablet, select "don't ask again for this network" and click "Yes". Please remember to do this after you have used the tablet to access the internet.
Geometrics instruments, such as G-864, MagEx, MagArrow, MagStation et al, communicate with a mobile device via WIFI. But because the instrument WIFI has NO internet access, some Android device, after connecting to the instrument for a while, will automatically start searching for another WIFI access point. To prevent this from happening, when the No Internet Access warning window pops up after first WiFi connection, choose "Tap for options". On the following window, check the “Don’t ask again for this network” Box and press “Yes” .
@geophysicist_burak Can you please upload some sample csv files to the folder below so that we can look into it:
File Upload
Thanks!
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