The 3DM-CV7-INS from developer MicroStrain, an HBK company, is a compact, lightweight, embeddable tactical-grade inertial navigation system (INS).
The INS integrates seamlessly with existing GNSS receivers to deliver a comprehensive position, velocity, and attitude (PVA) solution, maintaining accuracy even during GNSS signal losses. Read more >>
Choosing between NMEA, an industry-standard format, or MicroStrain’s binary packet protocol, MIP, depends on specific application requirements.
Field Applications Engineer Aidan Laracy conducted an in-depth evaluation to compare NMEA and MIP GNSS data input methods for the 3DM-CV7-INS, examining the balance between integration simplicity and precision.
NMEA Input: Simplicity & Speed
The most straightforward way to integrate GNSS data with the 3DM-CV7-INS is to use industry-standard NMEA data directly from an external GNSS receiver’s serial port. This method requires no software development; simply configure the 3DM-CV7-INS and connect a few wires to the receiver.
In one example, the 3DM-CV7-INS received NMEA data from a uBlox F9P with RTK fix. A 60-minute stationary test showed a standard deviation of 0.0153 m (North) and 0.0112 m (East).
However, the use of NMEA involves certain assumptions that limit the receiver’s full potential, resulting in slightly looser position data clustering. For applications needing greater flexibility in aiding measurements or higher precision, MicroStrain’s binary packet protocol (MIP) might be a better choice.
MIP Aiding: Accuracy & Versatility
MicroStrain’s MIP supports a wide range of external aiding data inputs to the 3DM-CV7-INS through its new aiding command set, including position and velocity in ECEF or LLH/NED formats, which are standard for many GNSS receiver outputs.
Additionally, the 3DM-CV7-INS can accept pre-processed body velocity data from lidar, radar, or optical flow sensors, as well as true heading measurements. These inputs provide more constraints against uncertainty growth during extended GNSS outages.
MIP’s design offers greater flexibility and precision, allowing specific uncertainties and validities to be defined rather than relying on general assumptions, as is necessary with NMEA. In testing, the 3DM-CV7-INS using MIP achieved a standard deviation of 0.0075 m (North) and 0.0066 m (East), surpassing the accuracy of NMEA.
Adaptable Integration Options for the 3DM-CV7-INS
For rapid development and swift deployment, NMEA messages deliver a complete PVA solution without additional software requirements.
While NMEA supports a robust navigation solution, it lacks the detailed data required for advanced GNSS/INS applications. Nonetheless, it remains an efficient option for quick setup and deployment without software development.
For applications where maximizing performance and refining product output is key, MIP aiding commands offer an ideal alternative. MIP aiding requires some software development to format GNSS data for MIP and connect with the 3DM-CV7-INS, but this method provides higher accuracy and greater adaptability than standard NMEA input.
Both NMEA and MIP methods offer distinct benefits. The MicroStrain 3DM-CV7-INS supports versatile GNSS data integration, with MIP aiding for applications that prioritize precision and performance, and NMEA aiding for simplicity and ease of integration.
For full test details and results, access the white paper here >>