Moving GNSS/INS Testing from the Skies to the Lab


Accurate, repeatable GNSS/INS simulations let you perform integration testing in the laboratory rather than in the field. As a result, you can shift project schedules to the left and accomplish more within existing budgets. This post will explain the limitations of field testing and how the right GNSS/INS simulator erases those limits.

Field testing imposes compromises

Testing GNSS/INS equipment in the field, on the face of it, should produce the most realistic results. After all, you’re putting the system through its paces in real-world conditions. In reality, real-world testing imposes compromises that limit a test program’s scope and accuracy.

Field testing strictly limits the range of conditions your project can study. Flying over the American Southwest does not reproduce high-latitude GPS reception. You must wait for nature to cooperate before evaluating performance in rain or snow. In addition, assessing resilience to jamming and other sources of RF interference takes considerable planning.

Another drawback to field testing is the number of variables affecting your results. Everything that could affect performance — vehicle motion, jamming, satellite visibility, atmospheric conditions, and more — happens simultaneously. Even with carefully-designed experiments, finding the root cause of unusual behavior is not straightforward. Moreover, field tests are not perfectly reproducible. You cannot re-fly a test point under the precise conditions of the original.

Designing a comprehensive test program to address these compromises is rarely practical. Field testing in several locations under a wide range of environmental and operational conditions is both time-consuming and expensive. Few integration projects can justify the time and expense.

Simulators deliver better results faster

By comparison, using a simulator’s output to stimulate GNSS/INS equipment in the lab makes integration projects more productive. You can conduct many more laboratory tests than in the field since there are no range issues and vehicles do not need refueling.

With room in your schedule for more tests, you can fully evaluate the equipment’s performance envelope. Virtually model extreme vehicle maneuvers without placing people at risk. Evaluate the equipment’s resilience to weather, interference, and terrain conditions anywhere on Earth without travel expenses — or entering hostile territory.

Simulators also produce more accurate and repeatable results. You have complete control over the configuration of each scenario. Specify conditions such as:

  • Number and visibility of GPS satellites.
  • Power, location, and timing of jamming events.
  • Terrain obscuration and multi-path RF reflections.
  • Vehicle trajectories.

Unlike field testing, sequential simulations will produce the same results given the same inputs. You can change a single setting to evaluate specific events.

Once bench testing is complete, adding a simulator to pilot-in-the-loop testing further raises confidence in the equipment’s readiness for integration. The simulator receives the pilot’s command inputs and stimulates the equipment based on the scenario’s terrain, interference conditions, and other settings.

Enhancing integration testing with CAST simulator solutions

Military and commercial customers alike rely on CAST Navigation’s decades-long history in GNSS/INS simulation. Our modular solutions let you combine the capabilities your project needs today while allowing expansion to support future projects. We also apply our expertise to simplify user interfaces without compromising the robustness of our simulation capabilities.

Flexible, scalable capabilities

CAST Navigation simulators provide robust capabilities for the integration testing of GNSS/INS receivers and antenna systems, including:

  • GNSS: Generate accurate, repeatable GNSS RF signals from modernized GPS as well as GLONASS and Beidou positioning constellations.
  • Inertial: Deliver high-rate inertial data to complex EGI and GNSS/INS systems.
  • Jamming: Create clean RF waveforms that precisely emulate natural, urban, and hostile interference.
  • CRPA: Test phased array antenna systems by sending precise, coherent, and repeatable RF signal wavefronts to each antenna element.

With CAST’s proprietary synchronization technology, you can link multiple CAST systems to run the most complex test scenarios.

Intuitive, comprehensive configurability

CAST Navigation simulators use a graphical interface that provides a single console for accessing each capability’s configurable settings. Software modules group related settings, allowing you to modify test parameters quickly.

Visual representations of the vehicle and terrain let you monitor the simulation in real-time. Overlays allow you to toggle vehicle trajectories, jamming sources, and other scenario elements.

Contact CAST Navigation to learn how these and other simulator benefits can improve your next integration project.

April 7, 2023