To us, there is no point to produce 2 readings if 2 sensors are right next to each other. We are open to discussions! 

An Export License is NOT required for shipment of cesium-vapor magnetometers to the following countries: Argentina, Australia, Austria, Belgium, Bulgaria, Canada, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, India, Ireland, Italy, Japan, Latvia, Lithuania, Liechtenstein, Luxembourg, Mexico, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Slovenia, Slovakia, South Korea, South Africa, Spain, Sweden, Switzerland, Turkey, and the United Kingdom. (Updated April 2019)

Export or re-export of the quoted items to Cuba, North Korea, Iran, Rwanda, Sudan, and Syria is prohibited by the US Dept. of Commerce as these are embargoed countries.

The MagArrow-SX is a special version of the MagArrow that has a reduced sensitivity in order to comply with US regulations and does not require an export license.

Please contact us us for more information

The MagArrow has two MFAM sensors, and the way they are arranged ensures that when one sensor is in its dead zone the other is at its optimum orientation, and vice versa. The readings from the two sensors are combined to produce one magnetometer reading only. The two sensor readings are weighted such that as one sensor approaches its dead zone it is weighted much less (down to zero in the dead zone) while the optimum oriented sensor is weighted more fully. Thus you get only one magnetometer reading with no dead zones whatsoever. In addition, the weighted averaging of the sensors still does partial heading error cancelling.

If you have another magnetometer, like the G-864, you can also measure the magnetic signature of the sensor part of the MagArrow with the following instructions.

Turn on the magnetometer

Wave the sensor part of the MagArrow above the magnetometer (as close as possible but not touching)

Wave in both west and east directions

Check whether this is any magnetometer reading change when the MagArrow passes by

If reading changes are observed, there must be some contamination.

What could possibly be an issue are the LiPo batteries, thermal cooling reduction at lower pressures, and the sealed MagArrow case.

MagArrow Case: While the body of the MagArrow is sealed tight, it is not sealed enough to puff out or get crushed with altitude changes. This hasn’t been tested.

LiPo Batteries: These are not altitude rated. The failure mode is shorted cells and fire.

Thermal Cooling: This could be measured in a pressure chamber using the internal temperature monitor diodes. We would have to rent time in the chamber to do the measurement. We might also make a stab at calculating the temperature increase. 30,000 feet is about 3 PSIA compared to 14 PSIA at sea level.

There is no altitude restriction on the MagArrow, but flying at high altitudes is taken at the users risk.

The MagArrow is a dual sensor magnetometer powered by MFAM sensors, but it is configured for use so it only has a single data output. The reason Geometrics has done this is so we could ensure the MagArrow encounters no "dead-zones". A dead-zone occurs when the orientation of a magnetometer results in the magnetometer producing poor or no measurements. The dead-zone angle depends on the location of survey.

Since we have the two MagArrow MFAM sensors in orthogonal orientations, the MagArrow Magnetometer has operability worldwide without affecting survey orientation, making it much easier to use for the customer.

Heading Errors

Heading errors are a type of noise magnetometers can experience. They come from three sources:

Sensor

Console

Operator

Magnetic materials in the sensor itself are the primary cause of heading errors. The physics of Cesium and Potassium magnetometers can contribute small amounts to the total heading error. Magnetic contamination near the sensors, operating electronics, or operator can all contribute to heading error.

Heading errors look like herringbone patterns in survey images. Alternate lines can also be corrugated.

Dead-Zones vs Heading Errors

while these two sources of error in magnetic data are different, there is overlap between them when operating a magnetometer like the MagArrow.

Heading errors can be fixed relatively easily in software, where dead zones can be much harder to manage. If a line is completely ruined because of a dead zone then they will need to re-fly the line/mission which is time consuming. Even with advanced users, these sorts of mishaps can happen.

Additionally, the closer a mag sensor operates to a dead-zone, the larger a heading error will be measured. With compensation software and a pre-survey heading error flight, heading error can be reduced dramatically to around 1 nT for the MagArrow.

Click to view the difference between Raw and Processed MagArrow Data

The MagArrow is only outputting a single value as a means to create a “no-dead-zone” system. Obviously each sensor has a dead zone themselves, but with the sensors orientated orthogonally at least one sensor at all times will have a magnetic measurement. By combining the measurements from both sensors it is possible to generate a constant magnetic field measurement independent of orientation and location in the world. If the data from each MFAM sensor in the MagArrow was individually reported there would be gaps in the mag fields observed by either sensor as you fly, rotate, and swing.

The heading effect can be mitigated through data processing. Geometrics recently published a peer-reviewed paper, explaining in detail the heading-effect compensation method. The paper can be found at https://library.seg.org/doi/abs/10.1190/tle41070481.1. A draft of the paper can be downloaded below.

After the compensation, the heading effect is removed and the new survey data is plotted below.

Geometrics also provide a preliminary data processing program for MagArrow and MagEx customers. Please refer to the other forum post below:

Survey Data Processing

Before you run the program, please download and install the LabView Runtime (free, 64-bit 2020 SP1) first:
https://www.ni.com/en-us/support/downloads/software-products/download.labview-runtime.html#369642

The user guide is also located in the folder. 

It is worth mentioning that the data processing program provides 2 methods of suppressing the MagArrow noise:
1. Through frequency filtering and line levelling (Survey Data Noise Reduction).
2. Heading effect compensation (Heading Error Compensation).

In general, to perform the heading error compensation, you need to collect heading effect calibration data (Instruction included in the folder).
It is possible that the calibration data can be obtained from the survey data itself.
If you have trouble processing your data, please share some of your data with Geometrics and we can provide help, especially in generating the calibration file.