The GPS antenna cable that ships with every 3DM-GX3-35 and 3DM-GX3-45 is 3 meters in length.

Cable length is important.  The longer the cable, the lower the signal strength.  If the user lengthens the cable, the signal strength will diminish.  The loss of signal strength can only be empirically determined by trying out a particular installation.  Loss of signal strength will manifest itself in the number of satellites seen, quality of data reception from satellites, etc.

No, the on-board GPS does not support this.... but if the user has a GPS that does, this external GPS can input its 'RTK-groomed' measurements into the 3DM-GX3-45 and the 3DM-GX3-45 will incorporate those measurements into the Kalman filter.  To be clear: the on-board GPS will be bypassed in favor of the external GPS.

Wikipedia's definition: http://en.wikipedia.org/wiki/Real_Time_Kinematic

Real Time Kinematic (RTK) satellite navigation is a technique used to enhance the precision of position data derived from satellite-based positioning systems, being usable in conjunction with GPS, GLONASS and/or Galileo. It uses measurements of the phase of the signal′s carrier wave, rather than the information content of the signal, and relies on a single reference station to provide real-time corrections, providing up to centimetre-level accuracy. With reference to GPS in particular, the system is commonly referred to as Carrier-Phase Enhancement, or CPGPS. It has application in land survey and in hydrographic survey.

LORD MicroStrain^® complete terms and conditions of sale may be found at: http://files.microstrain.com/terms-conditions-sale.pdf

To enable customers to try our standard products risk free, LORD 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. 30 day trial details may be found at: http://www.microstrain.com/support/warranty

LORD MicroStrain^® insures all products shipments to their full value unless the customer specifically states a different method.

The term ‘static’ accuracy refers to measurements made when the inertial unit is not moving and the on-board orientation algorithm has recovered from any sensor over-ranging.

The term ‘dynamic’ accuracy refers to measurements made while the inertial unit is moving and not exceeding the measurement range of the individual on-board sensors (accelerometers, gyroscopes, magnetometers).

The 3DM, 3DM-DH and FAS-A are designed to measure static rotations.

The 3DM-GX3 family is designed to measure both static and dynamic rotations.

Kalman Filter Performance

† RMS values generated from actual vehicle testing (airborne & land) when compared to a reference navigation unit

Attitude and Heading (AHRS)

GPS Receiver

Here is a link to a detailed technical note: http://files.microstrain.com/Orientation%20Conversion%20formulas.pdf

No – only one can be used at a time.  The device auto-senses which communication signal is attached (USB or serial), and only uses that channel for communications.

The 3DM-GX3 USB and RS-232 communication interfaces are built to satisfy the standard USB-IF and EIA specifications.  LORD MicroStrain^® provides 6 foot cables as standard.  Many techniques can be used to extend the length of the communication interfaces including powered USB hubs, USB boosters, RS-232 extenders, etc.

The 3DM-GX3 is calibrated at the factory.  The user is also provided with Hard and Soft Iron Calibration software to field calibrate the GX3 in situ.  This video further describes the function: http://www.microstrain.com/video/hard-soft-iron-calibration

Important note: Hard and soft iron calibration is not required for the 3DM-GX3-15 and the 3DM-GX315 OEM.  These units do not contain magnetometers.

From time to time the 3DM-GX3 may need recalibration. For example, as a result of coming in contact with magnetic influences (magnets, motors, etc.), residual magnetism may be picked up by the on-board components which will alter the calibration.  Another example: the 3DM-GX3 receives a severe shock, slightly altering the position of the circuit boards in relation to the enclosure, again altering the calibration.  In these cases the unit should be returned to the factory for recalibration.

Yes. Any number of units can be operated by a host at the same time. Several considerations surround this implementation (primarily computing power) and we suggest that you discuss your requirements with LORD MicroStrain^® sales or a support engineer.

Yes, there are no limitations.  However, if a user requires a ‘zeroing’ of the axes, this must be done in the user’s external application.  Good practice dictates that the orientation matrix be used to calculate such zeroing.  Please also be aware of the mathematical singularity in Euler angles.

The user should be aware that the Euler angle formulation in general contains a mathematical singularity at Pitch = +90 or –90 degrees. In practice, poor numerical results will be present if the Pitch angle exceeds +/-70 degrees. In applications where the Pitch angle cannot be guaranteed to exceed these values, it is recommended that the orientation matrix output be utilized instead.

The baud rate is user adjustable and may be set to 9600, 19200, 115200 (default), 230400, 460800, and 921600.

The following orientation outputs formats are available:

• Acceleration
• Angular Rate
• Magnetic Vector
• DeltaAngle and DeltaVelocity
• Orientation Matrix
• Quaternion
• Euler Angles (pitch, roll and yaw)
• ...and more.

A detailed description of these outputs can be found in the Data Communications Protocol manual of each product.

Yes. We provide a complete data communications protocol manual which describes in detail each and every command and response that is available with the device.  Applications may be developed in any programming environment (C, VB, LabVIEW, Linux, Matlab, etc.) which supports serial communication.

When you initially purchase a 3DM-GX3, a starter kit (SK) provides you with everything you need to get started! SKs include a 3DM-GX3 module, communication and power cables, software, manuals and GPS antenna if applicable.  In subsequent purchases you may only require additional modules or other individual components. Several communication interfaces are available creating several starter kit variations.

The GPS datasheet accuracy is CEP at 24 hours stationary, a common test condition for GPS.  CEP is a 50% confidence number.  Like other single (non-differential) GPS units, our accuracy is limited by constellation geometry, atmospheric, and clock error effects (largest contributors when selective availability is not included.)  This pegs best performance at approximately 5 meters RMS dynamic.  This is improved for areas where WAAS is enabled.

Yes, the antenna is powered at 3 Volts and draws 10 mA.

No, our GPS supplier does not produce modules without this limitation.

The attitude, position, velocity, and sensor bias states are all states within the same filter; therefore, they are calculated together.

The 3DM-GX3-45 implements a loosely-coupled filter that uses the GPS solution (position and velocity) as an input to the filter.

No.  A 3DM-GX3-35 can not be upgraded to a 3DM-GX3-45.

Yes.  The Theory of Operation document will be of interest.  It is available at: http://files.microstrain.com/3DM-GX3-45_Theory_of_Operation.pdf