The 3DM-GQ4-45 is a compact, tactical-grade all-in-one navigation solution with integrated GNSS and magnetometers, high noise immunity, and exceptional performance.

Product Highlights

High performance integrated multi-constellation GNSS receiver and MEMS sensor technology provide direct and computed PVA outputs in a small package

  • Triaxial accelerometer, gyroscope, magnetometer, temperature sensors, and a pressure altimeter achieve the best combination of measurement qualities
  • Dual on-board processors run a sophisticated Extended Kalman Filter (EKF) for excellent position, velocity, and attitude estimates
  • Improved position outputs with concurrent tracking of up to two GNSS constellations (GPS/QZSS, GLONASS, BeiDou)
Datasheet Manual
Where to Buy?
U.S. International OEM

List Price:
$4,795.00

Best in Class Performance

  • Fully calibrated, temperature-compensated, and mathematically aligned to an orthogonal coordinate system for highly accurate outputs
  • Bias tracking, error estimation, threshold flags, and adaptive noise, magnetic, and gravitational field modeling allow for fine tuning to conditions in each application
  • High performance, low drift gyros with noise density of 0.002°/sec/√Hz and VRE of 0.001°/s/g2RMS
  • Smaller and lighter than most tactical grade GNSS/INS units
  •  

    Ease of Use

  • User-defined sensor-to-vehicle frame transformation
  • Easy integration via comprehensive SDK
  • Common protocol between 3DM-GX3, GX4, RQ1, GQ4, GX5, and CV5
  •  

    Cost Effective

  • Out-of-the box solution reduces development time
  • High performance tactical grade outputs at an industrial grade price

General

Integrated sensors

Triaxial accelerometer, triaxial gyroscope, triaxial magnetometer, temperature sensors, pressure altimeter, and GPS receiver

Data outputs

Inertial Measurement Unit (IMU) outputs: acceleration, angular rate, ambient pressure, deltaTheta, deltaVelocity

Computed outputs:

Extended Kalman Filter (EKF): filter status, GPS timestamp, LLH position, NED velocity, attitude estimates (in Euler angles, quaternion, orientation matrix), bias compensated angular rate, pressure altitude, gravity-free linear acceleration, gyroscope and accelerometer bias, scale factors and uncertainties, gravity and magnetic models, and more. Complementary Filter (CF): attitude estimates (in Euler angles, quaternion, orientation matrix), stabilized north and gravity vectors, GPS correlation timestamp

Global Positioning System outputs (GPS): LLH position, ECEF position and velocity, NED velocity, UTC time, GPS time, SV. GPS protocol access mode available.

Inertial Measurement Unit (IMU) Sensor Outputs

 

Accelerometer

Gyroscope

Magnetometer

Measurement range

±5 g

300°/sec (standard)

±75, ±150, ±900°/sec (options)

±2.5 Gauss

Non-linearity

±0.03 % fs

±0.03 % fs

±0.4 % fs

Resolution

<0.04 mg

<0.0025°/sec

--

Bias instability

±0.02 mg

5°/hr

--

Initial bias error

±0.001 g

±0.05°/sec ±0.003 Gauss

Scale factor stability

±0.05 %

±0.05 %

±0.1 %

Noise density

50 µg/Hz

0.002°/sec/Hz

100 µGauss/Hz

Alignment error

±0.05°

±0.05° ±0.05°

Adjustable bandwidth

250 Hz (max)

160 Hz (max) --

IMU filtering

4 stage filtering: analog bandwidth filter to digital sigma- delta wide band anti-aliasing filter to (user adjustable) digital averaging filter sampled at 8 kHz and scaled into physical units; coning and sculling integrals computed at 1 kHz

Sampling rate

10 kHz

10 kHz

50 Hz

IMU data output rate

1 Hz to 500 Hz

Pressure Altimeter

Range

-1800 m to 10,000 m

Resolution

< 0.1 m

Noise density

0.01 hPa RMS

Sampling rate

25 Hz

Computed Outputs

Position accuracy

±2.5 m RMS horizontal, ± 5 m RMS vertical (typ)

Velocity accuracy

±0.1 m/s RMS (typ)

Attitude accuracy

±0.1° RMS roll & pitch, ±0.5° RMS heading (typ)

Attitude heading range

360° about all axes

Attitude resolution

< 0.01°

Repeatability

0.1° (typ)

Calculation update rate

500 Hz

Computed data output rate

1 Hz to 500 Hz

Global Navigation Satellite System (GNSS) Outputs

Receiver type

72-channel GPS/QZSS L1 C/A, GLONASS L10F, BeiDou B1, SBAS L1 C/A:WAAS, EGNOS, MSAS Galileo-ready E1B/C

GNSS data output rate

1 Hz to 4 Hz

Time-to-first-fix

Cold start: 27 sec, reacquisition: 1 sec hot start: <1 sec

Sensitivity

Tracking: -164 dBm, cold start: -147 dBm, hot start: -156 dBm

Velocity accuracy

0.1 m/sec

Heading accuracy

0.5°

Horizontal position accuracy

GNSS: 2.5 m CEP (autonomous)

SBAS: 2.0 m CEP (stationary, 24 hours, SEP 3.5 m)

Time pulse signal accuracy

30 nsec RMS

< 60 nsec 99%

Acceleration limit

≤ g

Altitude limit

No limit

Velocity limit

500 m/sec (972 knots)

Operating Parameters

Communication

USB 2.0 (full speed)

RS232 (9,600 bps to 921,600 bps, default 115,200)

Power source

+ 4.2 to + 28 V dc

Power consumption

2.5 W (-40 °C to +85 °C)

Operating temperature

-40 °C to +85 °C

Vibration limit

RMS, 10 Hz to2 kHz

Mechanical shock limit

750 (half-sine, 2 msec powered, any axis)

Physical Specifications

Dimensions

79 mm x 77 mm x 23 mm

Weight

105 grams

Enclosure material

Aluminium

Regulatory compliance

ROHS, FCC Class B, CE

Integration

Connectors

Data/power output: micro-DB9

GPS antenna: MMCX type

Software

MIP™ Monitor, MIP™ Hard and Soft Iron Calibration, Windows XP/Vista/7/8 compatible

Compatibility

Common protocol between 3DM-GX3, GX4, RQ1, GQ4, GX5, and CV5

Software development kit (SDK)

MIP™ data communications protocol with sample code available (OS and computing platform independent)

 

  • Launch MIP Monitor and connect to the inertial sensor as normal.
  • Click Settings.
  • Click Load Default Settings and a confirming message box appears.
  • Click OK and the message box disappears.

The inertial sensor is now set to the factory default settings.

Yes, we have mounted a downloadable STP (STEP) file on the Documentation tab of this product web page.

Although the inertial sensor’s magnetometer is calibrated at the factory to remove any internal magnetic influences in the device, measurements are still subject to influence from external magnetic anomalies when the sensor is installed. These anomalies are divided into two classes: hard iron offsets and soft iron distortions. Hard iron offsets are created by objects that produce a magnetic field. Soft iron distortions are considered deflections or alterations in the existing magnetic field. Ideally, these influences are mitigated by installing the sensor away from magnetic sources, such as coils, magnets, and ferrous metal structures and mounting hardware. However, often these sources are hard to avoid or are hidden. To mitigate this effect when using the magnetometer to aid in heading estimations, a field calibration of the magnetometer after final installation is highly recommended.

All of the filters mentioned above are “estimation filters” (EF). When talking about estimation filters, one can quickly get mired in alphabet soup.

 

A Kalman Filter (KF) is a linear quadratic estimation algorithm that operates recursively on noisy data and produces an estimate of a system’s current state that is statistically more precise than what a single measurement could produce.

 

An Extended Kalman Filter (EKF) is used generically to describe any estimation filter based on the Kalman Filter model that can handle non-linear elements. Almost all inertial esti­mation filters are fundamentally EKFs.

 

An Adaptive Kalman Filter (AKF), technically speaking, is also an EKF but it con­tains a high dependency on “adaptive” elements. “Adaptive” technology refers to the ability of a filter to selectively trust a given measurement more or less based on a “trust” threshold when compared to another measurement that is used as a reference. The 3DM GX4-25 and -15 rely on adaptive control elements to improve their estimations and hence we refer to the estimation filter used in those devices as an “AKF”. Technically speaking it is an “EKF with heavy reliance on adaptive elements” or possibly an “Adaptive Extended Kalman Filter”. We just call it an AKF.

 

An Auto-Adaptive Extended Kalman Filter (AA EKF) is an adaptive EKF that, like the AKF described above, has “adaptive” elements that selectively trust given measurements more or less based on comparison to reference inputs. The difference with the auto-adaptive filter is that the “trust” thresholds are automatically determined by the filter itself. The filter collects error metrics on all the measurements and uses this to determine appropriate trust thresholds. This feature makes tuning a Kalman Filter for optimum performance much easier than manually determining these thresholds. The GX5/CX5/CV5 series introduces the Auto-Adaptive feature whereas the GX4 series has fixed adaptive thresholds.

 

A Complementary Filter (CF) is commonly used as a term for an algorithm that com­bines the readings from multiple sensors to produce a solution. These filters usually contain simple filtering elements to smooth out the effects of sensor over-ranging or anomalies in the magnetic field.

The MEMS gyroscopes used on the LORD Sensing MicroStrain Inertial sensors are very high quality automotive/industrial grade gyros that have excellent temperature, linearity, and bias stability characteristics. They have very low noise and are stable over a wide range of dynamic conditions. However, like all MEMS gyros, there are conditions that can cause the zero-bias value to change.

 

Click here for a technical note that details this subject and instructs the user on how to use the “capture gyro bias” function to maintain the accuracy of the inertial sensor.

Using MIP Monitor software, make all the settings that you are normally applying to the inertial sensor.

When those are in place, do the following.

  • Click Settings.
  • Click Export Settings and the Choose or Enter Path of File window appears.
  • Accept the default File Name.
  • Note what directory is in place (so you can retrieve the file).
  • Click OK, the window closes, and a "Settings" file with a name like 3DM-GX5-15 6254.62027 Settings 6-7-2018 1-34-16 PM.ini is written.

 

This SETTINGS file can now be set aside and imported into the inertial sensor at another time.

 

This SETTINGS file is also valuable in aiding LORD Sensing MicroStrain to support you when troubleshooting problems.

Yes, the inertial sensor programming interface is comprised of a compact set of setup and control commands and a very flexible user-configurable data output format. The commands and data are divided into 4 command sets and 3 data sets corresponding to the internal architecture of the device. The four command sets consist of a set of “Base” commands (a set that is common across many types of devices), a set of unified “3DM” (3D Motion) commands that are specific to the LORD Sensing MicroStrain inertial product line, a set of “Estimation Filter” commands that are specific to LORD Sensing MicroStrain navigation and advanced AHRS devices, and a set of “System” commands that are specific to sensor systems comprised of more than one internal sensor block. The three data sets represent the three types of data that the inertial sensor is capable of producing: “IMU” (Inertial Measurement Unit) data, “GPS” (Global Positioning Sensor) data, and “Estimation Filter” (Position, Velocity, and Attitude) data. The type of estimation filter used in the inertial sensor is an Extended Kalman Filter (EKF).

 

Base commands: Ping, Idle, Resume, Get ID Strings, etc.

3DM commands: Poll IMU Data, Poll GPS Data, etc.

Estimation Filter commands: Reset Filter, Sensor to Vehicle Frame Transformation, etc.

System commands: Switch Communications Mode, etc.

 

IMU data: Acceleration Vector, Gyro Vector, etc.

GPS data: Latitude, Longitude, UTC, Satellites in view, etc.

Estimation Filter data: Position, Velocity, Attitude, Acceleration Estimates, etc.

 

The protocol is packet based. All commands, replies, and data are sent and received as fields in a message packet. Commands are all confirmed with an ack/nack (with a few exceptions). The packets have a descriptor type field based on their contents, so it is easy to identify if a packet contains commands, replies, IMU data, GPS data, or Estimation Filter data.

LORD Sensing MicroStrain warrants this product to be free from defective material and workmanship for a period of one (1) year from the original date of purchase. LORD Sensing MicroStrain agrees to repair or replace, at its sole discretion, a defective product if returned to LORD Sensing MicroStrain within the warranty period and accompanied by proof of purchase. This warranty does not extend to any LORD Sensing MicroStrain products which have been subject to misuse, alteration, neglect, accident, incorrect wiring, mis-programming or to use in violation of operating instructions furnished by us, nor extend to any units altered or repaired for warranty defect by anyone other than LORD Sensing MicroStrain. This warranty does not cover any incidental or consequential damages and is in lieu of all other warranties expressed or implied and no representative or person is authorized to assume for us any other liability in connection with the sale of our products. Some states do not allow limitations on how long an implied warranty lasts, and/or the exclusion or limitation of incidental or consequential damages so the above limitations and exclusions may not apply to the original customer.

To enable customers to try our products risk free, LORD Sensing MicroStrain offers a 30-day return on the purchase of a starter kit. In order to take advantage of this offer, a purchase order or payment for the starter kit is required when the order is placed. If the product is not suited to the application, the product may be returned within 30 days from the date of receipt for a full refund (excluding shipping and handling), as long as the product is unaltered or undamaged. Items can only be returned after LORD Sensing MicroStrain has issued an RMA. Items must be packed to withstand shipping and returned freight pre-paid. LORD Sensing MicroStrain will inspect the items returned and issue a refund or credit once the items have been examined and are deemed to be unaltered or undamaged. Non-standard or custom products may only be returned with LORD Sensing MicroStrain's approval and a re-stocking penalty may be assessed.  A 30-Day Return must be initiated by receiving an RMA (Returned Merchandise Authorization from LORD Sensing MicroStrain.

The Terms and Conditions of Sale for this inertial sensor can be found here.

When you receive your inertial sensor, you can immediately begin operating it with our MIP MONITOR software.

MIP Monitor is a Microsoft Windows-based out-of-the-box software utility that allows the user to fully configure, operate, display, and write data to file.

Many users will be able to accomplish their use of the inertial sensor with just MIP Monitor.

Click here to download MIP Monitor.

If one was to attempt dead reckoning, one would follow this path:

 

1: The inertial sensor provides acceleration with respect to its body-fixed coordinate system. This must be transformed into a coordinate system fixed to the earth. In order to accomplish this, it is necessary to know the orientation of the inertial sensor relative to the earth-fixed coordinate system.

 

2. Subtract the gravity vector.

 

3. Double integrate (WRT time) the acceleration.

 

Note that any small errors in either the orientation estimate, or the sensor’s acceleration bias, or the knowledge of the gravity vector will result in exponentially increasing errors. The size of these errors has no bounds.

 

We generally do not recommend our sensors for applications involving position measurement due the exceptional difficultly of such computations.

Even the best systems, costing hundreds of thousands of dollars, are subject to error accumulation on the order of 1 kilometer per hour.

The bias errors of the industrial grade accelerometers used in the inertial sensor will produce errors of many kilometers within seconds.

This assumes that the orientation is known perfectly.

Uncertainty in the orientation measurement will make the errors even larger.

 

These inertial instruments use MEMS sensors (accelerometers, gyroscopes).

These MEMS sensors are classified as 'automotive' or ‘industrial’ grade.

They are not 'tactical' or 'navigational' grade.

 

The bottom line is that the inertial sensor cannot directly provide a displacement measurement.

 

Let us also be very clear that this statement is not meant to dissuade you; it is meant to set the tone for the complexity involved in this application.

 

Papers such as this discuss the science involved in great detail: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwiCsraTjO3RAhWj24MKHXIvBIAQFggaMAA&url=https%3A%2F%2Fsciforum.net%2Fconference%2Fecsa-1%2Fpaper%2F2395%2Fdownload%2Fpdf&usg=AFQjCNEqcxQZFt3dmpiyKJOTzcNXiwgnzA&cad=rja[na01.safelinks.protection.outlook.com]

Vibration impacts MEMS-based inertial sensors; this is true for our inertial sensors or any other manufacturers.
Every effort must be made to eliminate vibration.
Vibration in the environment frame can significantly degrade the performance of the inertial sensor, particularly constant, unchanging vibration.
Strong, continuous vibrations appear as unaccounted noise to the filter, degrading its performance.
The accelerometers can't tell the difference between vibration and acceleration, and therefore the filter receives erroneous input.
We would suggest using some vibration damping materials to mount the inertial sensor.
Here are some product manufacturers:
·         http://www.earsc.com/
·         http://www.sorbothane.com/
Here is an on-line source for ordering small quantities, small squares of material: http://www.mcmaster.com/#ultra-soft-polyurethane/=gai91i
The idea is to place the pad between the vehicle frame and the inertial sensor to isolate the inertial sensor.

There are many ways to physically accomplish this damping.

As an example, you could mount the inertial sensor on the aluminum plate and place a Sorbothane pad between the plate and the vehicle frame.

Sorbothane can be purchased with double-sided adhesive.
Be careful not to defeat the isolation by using through-bolts that transfer the vehicle frame vibration to the inertial sensor (or in this example, the aluminum plate holding it).

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