Defining fidelity in Simulators

A major concern in planning a simulator for training is whether to go all-out and implement custom hardware, making the simulator as close a copy of the machinery being simulated as possible, or to create a lightweight representation that has functional equivalents for major systems, saving on cost what you lose in fidelity. Three parameters define the overall fidelity and accordingly, cost of development, in simulators.

1. Functional fidelity is a measure of how well we emulate the user input -> System Response -> Output to User chain. Creating functional equivalence can be as simple as coding a few equations to approximate physics, or as complicated as replicating the entire code and hardware responses of a complex control system. This is also the area where most of the unavoidable cost and development time arise.

2. Audio-visual fidelity is a measure of how realistically the environment is presented to the user in terms of visuals and audio cues. Budgeting for Visuals and Audio is a well-trodden road, and there are multiple methods to reduce costs and to cater to your particular budget.

Sim Low vs high visual fidelity

Example of Low vs High Visual Fidelity in a Flight Simulator

3. Physical fidelity is a measure of how closely the interface to the simulator resembles that of the actual simulated machine. E.g. when simulating a switch, a touch interface has a higher physical fidelity than one based on mouse movements, while an actual physical switch has the highest fidelity. Perfectionism in this aspect of simulator development can greatly inflate your budget and you can save a lot of cost and reduce risk considerably if you implement the interface smartly.

Simulating a spacewalk on the ISS, low vs high physical fidelity

Simulating a spacewalk on the ISS, low vs high physical fidelity


Cost breakdown based on simulation quality levels

So how does a simulator project breakdown look like based on the three parameters above? Based on my own experience and reports from friends who work on similar projects in a wide variety of fields, this is what I have found:


Simulation project cost estimation based on how much fidelity is required

Simulation project cost estimation based on how much fidelity is required

Note the above are just rough estimates of the cost breakdown, but there are a few trends that are easy to spot:

1. Increasing a project’s fidelity, particularly physical and visual fidelity by a step can increase costs by a lot.

2. Physical fidelity costs rise very quickly the closer you try to emulate the original object

3. Audio/visual fidelity costs go up fast too, but not as badly as physical fidelity.

This means that in order to keep costs low, you need to limit physical, and audio/visual fidelity to what is absolutely necessary. Additionally, if you can achieve our training goal with a lower overall fidelity, you should not aim higher initially. I would suggest developing a low-fidelity simulator, and getting real-world data on training efficacy, before moving up to the next step. While some of the visual or physical assets will not be reusable for a later upgrade, most of the functional simulation will.

Now that we have established increased physical fidelity as the major culprit in inflated simulator costs, let’s see what can be done about it.

How much physical fidelity is enough?

The answer to this question really depends on the situation. Mimicking the hardware as much as possible allows trainees to gain muscle memory and test the limits of their physical abilities in a realistic environment. For critical missions, like those performed by astronauts in orbit, recreating as much of that environment as physically possible makes sense. On the other hand, a race for maximal hardware parity can lead to budget over-estimations and hence project abandonment. The efficacy of simulators as a learning tool has been proven by many studies, thus it is worth looking at possibilities to capture the essence of the learning experience they provide, at the lowest possible cost to the organization. To understand what features can be scrapped without losing a whole lot of training value while seriously cutting down cost, let’s have a look at the benefits of high hardware fidelity:

  • The tactile sense of realistic hardware controls helps train muscle memory. (commercial haptic feedback devices are still way behind the curve compared to other user interface technologies)
  • Touch – there is no way to convey low-frequency vibration. (high frequency vibration can be conveyed by sound), etc. (e.g. in an HVAC or car repair simulator)
  • Secondary and tertiary effects that would be too hard to simulate in software. E.g. a very cold pipe in the real world will form condensates on it – this would have probably not been simulated in a normal simulator, thus the cue would not be available to the trainee.
  • Intuition is developed far better due to the multi-sensory environmental cues in a hardware based simulator and in the real world, compared to software sims.
  • Software sims depend on a level of abstraction and not all actions involved will be simulated, e.g. in a 2D simulation of a rotary gauge, the parallax effect will be “abstracted out” hence the user never learns how avoid this effect.  (3D sims can of course teach this)
  • It is doubtful that cheap generic hardware for simulating full-body vibration, angle of body, gravity, acceleration, etc. will become commercially available. This means that ultra-realistic flight simulators e.g. where such effects are important (e.g. an airplane shaking violently might require input from the pilot) will still require expensive hardware.

Aside from cost reduction, moving towards software-only solutions with a lower physical fidelity offers other benefits:

  • Software-only controls allow for easy modifications without incurring any manufacturing of custom parts
  • software-only solutions can be installed on multiple machines and used by many users concurrently
  • software-only simulators ride the wave of advancement driven by gaming and software technology – much faster than advances in manufacturing, miniaturization and machining
  • software-only solutions allow for simulating machinery that is still in early design and planning stages and provide invaluable information to interface designers
  • software based solutions generally have a much lower cost to operate and a negligible maintenance cost


If you are looking to create a simulator for a vehicle, equipment or a skill/process, start by implementing a low fidelity (particularly physical and visual) solution. In most cases this can be done on a very low budget in the tens of thousands to hundreds of thousands of dollars. Once you have evaluated the training efficacy for your target audience, it is easy to ramp up visual and in particular, functional efficiency. Avoid increasing physical fidelity until you have reasonable proof that it is absolutely critical.


Skill acquisition in children is achieved through repetition. In order to motivate such repetition, while maximizing the number of new situations that child encounters, juvenile mammals have evolved the concept of “play”. Despite our natural tendency to pick up skills via play – which is arguably little more than abstracting real life situations, simulating them, and competing for results – educational systems developed based on ideologies and untested “laws” have not used “play” to its fullest potential. As education moves towards an experiment-oriented science, we are seeing more and more positive results using play not only for children, but also in adult education. I argue that simulation, especially ‘motivated’ simulation is indistinguishable from play, and shares the same pedagogical benefits, and you don’t need to take my word for it – an entire industry has sprung up under the catch-all phrase of “gamification” that attempts to monetize the motivational aspects of play in corporate settings, and with the goal of increased productivity.

Education has come a long way in the past few centuries. For the general population skills have been traditionally acquired during apprenticeships. With the industrial revolution and widespread primary education, this moved partially to classrooms, although the content of such education started to divert from productive skills to theoretical knowledge. Cheap books allowed for self-study, and libraries in large cities promoted it especially among scholars, but here too, most books nurtured theoretical rather than practical knowledge.  When computers started to enter homes, there was new hope that the power of multimedia and simulations will allow for accelerated learning in schools, industry and everyday life, however, when Computer-Based Teaching didn’t deliver on it’s promise many concluded that new media could not replace entrenched traditional methods of education – others tried to find out why CBT had failed its promise. Some of the better studied reasons include:

Besides the cost of technology, motivation and the requirement for teachers/trainers to control the learning experience are two major factors holding e-Learning back, and Simulations along with some elements of competitions and game design are perfectly poised to solve those problems. The chart below shows the generally accepted performance comparison with regards to known learning platforms:

educational value of training methods

  • Simulators allow users to be motivated by their unique ability to instantly gauge the user’s success or failure, and provide extrinsic motivation (e.g. through awards, points, etc.) and intrinsic motivation by allowing a the user to experience and learn in a safe environment isolated from real-world pressures. Once skills are learned, other challenges such at time limits, equipment limits, etc. can be added to the simulation.
  • Software-based simulators can be run repeatedly by the user with no incremental cost to the operator.
  • The instant feedback offered by simulators maximizes learning and memory retention.
  • Testing for skill acquisition or certification can easily be embedded in the simulator – no additional paper- or computer-based test will be necessary to gauge if the user has learned the skills.
  • Since simulators can be made to closely resemble the real world, they offer a good one-to-one basis for acquiring skills. Audio-visual and functional parity with real-world equipment and environments ensures transferability of skills to real-world situations.
  • Retention of skills can be maximized by keeping the user interested in part due to the high motivation levels that can be achieved with simulators. Additionally, simulation-based training can be accessed at any time in the user’s career if they need to brush up on skills.


As can be seen, interactive simulation is the best known solution to training we have come up with so far, and it provides the highest level of skill transfer at the lowest cost. Computer software and hardware is advancing at a fast rate, and educational technology will benefit greatly by hitching a ride on this progress.


Learning in The Matrix
Thirty years ago we would gawk at the simple vector drawings on screens that represented buildings, terrain, mountains and trees in flight simulators. Those giant multimillion hydraulically driven machines were the envy of every kid dreaming of becoming a pilot. Those flight simulators were custom-built, expensive to operate, and while they looked great with all the buttons and panels and switches, they “boasted” the same lack of ergonomics in design as real airplane cockpits did.

Twenty years ago, PCs became cheaper and more powerful. Tools to create nice graphics became available, and the concept of CBT (Computer Based Training) Took off. by using images, small video, and flash technology, companies were able to create training material cheaply, and spread it far and wide. In parallel, video gaming started to see first releases of simulators for airplanes, spaceships, etc. that look much better and had a balanced degree of realism compared to commercial sims. Unfortunately CBT and Simulation games grew apart, and denied us the best of both worlds: Cheap, stunning, easy to use interactive training simulations!

Ten years ago, militaries across the globe started to adopt interactive simulations as a serious means of training for vehicle operations, tactics and strategic decision making. Requiring lengthy certifications and complex standards, meant that the technology used in such simulators was behind the tech curve by at least three years. Game engines still cost millions and were hard to license, and CBT and web-based learning had reached its limits of usefulness. While some visionaries saw the potential of visually rich and interactive simulators for training in any skill, most companies were disillusions and didn’t believe such training to be available or effective.


Simulators Then…

modern A380 cockpit simulator
  …Simulators Now

That future has arrived. Interactive 3D simulations are better, cheaper and more useful than ever. They are being applied to many industries, from mining to shipping, from the military to peace organizations, from basic skills like welding to complex soft-skills like ethics and management. A sim that would have cost millions to make just a decade ago, can now be produced with better graphics, realistic physics, and complex dynamics at one-tenth that cost. Game engines are commercially available to anyone, and a huge number of software developers, 3D artists, and users are proficient at using them. Innovative input systems such as the Kinect and glove controllers have matured in just the last ten years and multiple companies are working on the future of lightweight hi-res wearable virtual reality goggles. Fully interactive virtual reality training has arrived, has proven effective,  and is here to stay – it’s now up to visionary managers to start adopting these technologies.

Humans gain skills by repeatedly performing tasks and getting feedback on them. Interactive simulations are currently the cheapest, fastest and only scalable platform we know of for teaching skills, and even if direct skill downloads may never become possible, the infrastructure to efficiently deliver skills on demand is certainly taking shape.