{"id":3567,"date":"2026-10-21T22:07:46","date_gmt":"2026-10-22T10:07:46","guid":{"rendered":"https:\/\/footworklab.net\/?p=3567"},"modified":"2026-10-22T15:02:24","modified_gmt":"2026-10-23T03:02:24","slug":"how-plantar-pressure-mapping-works","status":"publish","type":"post","link":"https:\/\/footworklab.net\/fr\/news\/3567\/","title":{"rendered":"How Does Plantar Pressure Mapping Work? The Sensor Layer Explained Plainly"},"content":{"rendered":"
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About the author<\/strong> \u2014 FOOTWORK LAB is a manufacturer of foot assessment equipment and custom orthotic insoles, based in Ruichang, Jiangxi Province, China. Founded in 2014, with its own production plant since 2018. Certified to European Union and ISO quality system standards. See the factory<\/a> or view certification<\/a>.<\/p>\n<\/div>\n

A pressure map looks like a photograph of something that is happening under the foot, and that resemblance is the source of most misunderstandings about it.<\/strong> It is not a photograph. It is a grid of inferred values, produced by a layer of material that changes electrically when it is squeezed, read by electronics that scan the grid in sequence, and rendered by software that has to decide what to draw between one measuring point and the next. Every one of those steps involves a choice, and every choice leaves a trace in the image.<\/p>\n

Understanding the chain matters commercially as much as clinically. Buyers comparing systems are usually handed a colour image and a list of features, and the image is persuasive precisely because nobody asks how it was made. A practitioner who knows where the numbers come from reads the map differently: they know which parts of it are measurements, which parts are calculations, and which parts are conventions that two systems might implement differently.<\/p>\n

This article explains the sensor layer in plain terms, without quoting any figures from our own hardware. Our systems are plantar pressure measurement systems: a pressure-sensing layer, camera posture capture and analysis software. What follows is how that class of instrument works in general, and where its limits sit.<\/p>\n

What the sensing layer physically is<\/h2>\n

At its simplest, the layer is a sandwich. Two sheets carry electrical conductors arranged as rows and columns. Between them sits a material whose electrical behaviour changes when it is compressed. At every crossing of a row and a column there is, in effect, a small sensing point, and the electronics can address each one by selecting a row and reading a column.<\/p>\n

Three material families do most of this work. Resistive layers change resistance as the conductive particles inside them are pushed closer together. Capacitive layers change the capacitance between two conductors as the gap between them narrows. Piezoresistive materials change resistance in a way that responds quickly to changing load, which matters when the client is walking rather than standing. Each family has a different personality: different sensitivity at low load, different behaviour when load is applied for a long time, different tolerance for being bent.<\/p>\n

The layer is not the instrument on its own. It needs a substrate to keep the geometry stable, a surface that grips the foot or the sock so the client does not slide, and a housing that stops the whole assembly from flexing under a standing adult. A sensing sheet that is allowed to bend changes its own calibration as it bends, and the resulting map is a picture of how the plate itself bends as much as of the foot.<\/p>\n

That is why plate construction dominates the cost of this category far more than the sensing material does. A rigid, flat, well-supported surface with a stable layer on top produces data that can be trusted for years. A flexible mat produces data that is useful for screening and difficult to compare across sessions. Neither is dishonest, but they answer different questions.<\/p>\n

From squeeze to number: the measurement chain<\/h2>\n

The electronics scan the grid continuously, converting the electrical state of each crossing into a value. That value is not pressure yet. It is a raw signal, and converting it requires a calibration: a known load applied to known points, recorded, and used to build the link between signal and load.<\/p>\n

Calibration is where two systems start to diverge. A factory calibration performed on a press is reproducible and traceable; a field calibration performed by standing on the plate is convenient and depends on the person doing the standing. Ask any supplier how calibration is performed, how often it should be repeated, and what happens to the data if the layer ages. A system that has no answer to the third question will drift quietly and produce comparisons that are not comparisons.<\/p>\n

Several physical effects sit between the sensor and the truth. Creep is the tendency of a loaded material to keep settling slowly under a constant load, which makes a long standing capture read slightly differently at the end than at the beginning. Hysteresis means the reading depends on whether the load is increasing or decreasing. Temperature changes the electrical properties of most sensing materials, which is why a plate near a window or a heater behaves differently in the afternoon. Crosstalk means load on one point influences the reading at a neighbour.<\/p>\n

None of these effects can be eliminated. They can be characterised, compensated in software, and disclosed. That is the honest description of what a good system does: it knows its own error behaviour and manages it. When a supplier presents a pressure map as exact, the useful response is to ask what the repeatability is between two captures of the same client in the same position, because that number is the honest measure of what the instrument can support.<\/p>\n

The last step in the chain is the interpretation the software performs before a human sees anything: masking regions of the foot, locating the peak, computing a centre of pressure, comparing left with right. These are calculations, not measurements, and they carry assumptions. Knowing which is which is the difference between reading a map and being persuaded by one.<\/p>\n

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FOOTWORK LAB FX custom orthotic insoles. Product photography of our own output; specifications are confirmed in writing before an order.<\/figcaption><\/figure>\n

Why the map looks the way it does<\/h2>\n

The colour scale is the first convention to understand. There is no universal colour for a given pressure; the software maps the range of values in the current capture onto a palette, or onto a set palette chosen by the operator. On an auto-scaled image, a light client and a heavy client can produce identical colours while loading the plate very differently. That single fact explains a large share of mistaken comparisons between sessions.<\/p>\n

Ask which scaling mode is in use, and insist on the same mode across visits. A consistent scale makes comparisons honest and makes some captures look dull. An auto scale makes every capture look dramatic and makes comparison unreliable. Most software offers both; the trap is not knowing which one produced the image in front of you.<\/p>\n

The second convention is interpolation. The grid has gaps between its measuring points, and the software fills them by estimating. Smooth, continuous gradients look convincing and are partly invented. A blockier rendering is closer to the raw data and less pleasant to look at. Neither is wrong, but a practitioner who believes the smooth version is the measurement is reading the software’s imagination as though it were the foot.<\/p>\n

The third convention is the outline. Many systems draw a foot shape around the data, either from the pressure footprint itself or from a separate capture. That outline helps the eye orient, and it can also mislead, because a foot outline drawn from a thresholded pressure map is not the same as the anatomical foot. When the toes do not register, the drawn shape ends where the toes should be, and a reader who does not know that will describe a short foot.<\/p>\n

The fourth is smoothing over time. A dynamic recording is usually filtered, and the amount of filtering changes what the peak looks like. Heavy smoothing produces a calm, readable animation and hides brief high loads. Light filtering shows the spikes and is harder to watch. Ask what the default is, and ask whether the displayed peak is a single sample or an average over a window.<\/p>\n

Static and dynamic: two different recordings<\/h2>\n

A static capture asks where the load sits while the client stands still. It is the closest thing this class of instrument has to the footprint on a plate, with the addition of magnitude. It is quick, easy to explain, and repeatable enough to compare across months, which makes it the workhorse of a screening workflow.<\/p>\n

A dynamic capture asks how the load moves. The client walks across the plate, or over a platform, and the system records a sequence of maps that can be played back. The useful outputs are a sequence of frames, a trajectory of the centre of pressure, and regional summaries over the course of a step. This is where the instrument earns its place in a gait-oriented practice, because the question “where does the load go” cannot be answered by a standing capture.<\/p>\n

The two are not interchangeable and they do not always agree. A client who stands with an even distribution can walk with a marked asymmetry, and the reverse happens too. A practice that captures only one of them is describing half of the picture, and a practice that captures both has to decide which one drives its decisions. Our own recommendation is to capture standing first, because it is quick and it establishes a baseline, then to add a walking capture when the consultation has time for it.<\/p>\n

Barefoot and shod are also different tests. A shod capture tells you what the shoe is doing to the load; a barefoot capture tells you what the foot is doing on its own. Both are useful and neither substitutes for the other. If your workflow involves footwear or insole design, the shod capture is the one that matches the client’s actual condition, and the barefoot capture is the reference.<\/p>\n

Repeatability deserves a sentence of its own. Two captures of the same client, taken minutes apart, will differ. The difference is the instrument’s noise floor plus the client’s natural variation, and it sets the smallest change you can honestly claim to see between visits. Any practice that intends to show a client their progress should establish that floor early, by capturing the same client twice in one session and looking at how much the map moves.<\/p>\n

Where the camera channel fits<\/h2>\n

A pressure map describes the foot’s contact with a surface. It says nothing about what is happening above the ankle, and in a standing client a great deal of what the foot is doing is a response to the position of everything above it. That is the gap the camera channel fills.<\/p>\n

In our systems the camera records the client’s standing posture and the alignment of the lower limb during the same session as the pressure capture. The software presents that view alongside the pressure data, so the practitioner can look at the loading pattern and the standing position together rather than reconstructing one from memory of the other. The division of labour stays the same: the system records, the professional interprets.<\/p>\n

The practical value is in the correlation. A foot that loads heavily on one side while the standing position above it leans the same way is telling a coherent story. A foot that loads heavily on one side while the body above it is symmetrical is telling a different one, and the practitioner needs both facts to decide which. Without the camera, that comparison depends on the practitioner’s eye and memory, which vary.<\/p>\n

It is worth being clear about what the camera does not do. It does not measure joint angles in a way that replaces a hands-on examination, it does not track movement during walking in the way a multi-camera laboratory does, and it does not produce a conclusion. It produces a second channel of evidence, captured at the same moment as the first, which is more than most consultations currently have.<\/p>\n

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FOOTWORK LAB FX custom orthotic insoles. Product photography of our own output; specifications are confirmed in writing before an order.<\/figcaption><\/figure>\n

What the map cannot tell you<\/h2>\n

It cannot tell you whether the pattern matters. A map reports where load sits; it does not know whether that distribution is a problem for this client, in this body, with this history, at this age and with this occupation. That judgement requires a qualified professional and a conversation, and no amount of colour resolves it.<\/p>\n

It cannot tell you about load inside the shoe in a way that generalises to another shoe. The plate is a rigid surface, and a shoe’s midsole is not. A capture taken on a plate describes the client on that plate. It is a reference point, not a prediction of what happens in a running shoe on a road.<\/p>\n

It cannot separate load from tolerance. Two clients with identical maps may have completely different experiences, because pressure that one person finds unremarkable another finds intolerable. The instrument measures the load; the tolerance lives in the person, and it is elicited by asking.<\/p>\n

It cannot resolve shear. Most systems in this category measure vertical load, and the forces that act sideways along the surface are largely invisible to them. A practitioner who reads a map as a complete description of what the foot experiences is over-reading it.<\/p>\n

And it cannot substitute for a record that is kept consistently. The most common failure in this category is not a bad instrument but an inconsistent routine: different stance, different scaling, different shoes, different operator, and then a comparison that means nothing. The technology is the easy part. The protocol is where the value is, and the protocol is free.<\/p>\n

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FOOTWORK LAB FX custom orthotic insoles. Product photography of our own output; specifications are confirmed in writing before an order.<\/figcaption><\/figure>\n

Frequently asked questions<\/h2>\n
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Does the system measure pressure or force?<\/h3>\n

The layer responds to load at each sensing point, and the software converts that into pressure by accounting for the area each point represents. Force is what the layer physically feels; pressure is the derived quantity, which is why calibration and area assumptions both matter.<\/p>\n

Why do two captures of the same client look different?<\/h3>\n

Because the client is not a rigid object and the layer has a noise floor. Small changes in stance, breathing and weight shift move the map. Capture the same client twice in one session and compare, so you know how much movement is normal before you read anything into a change between visits.<\/p>\n

Is a smoother map more accurate?<\/h3>\n

No. Smoothing is interpolation between measuring points and filtering over time. It makes an image easier to read and further from the raw data. A blockier rendering is closer to what was measured, which is why it is worth knowing which display setting produced the image you are looking at.<\/p>\n

Can the same plate capture standing and walking?<\/h3>\n

Yes, and both are useful, though they answer different questions. A standing capture shows where load sits at rest; a walking capture shows how it moves. They do not always agree, and a practice that captures only one is describing half of the picture.<\/p>\n

Do we need the camera channel if we already have the pressure data?<\/h3>\n

It depends on what you do with the data. The camera records posture and alignment in the same session, which lets you read the foot’s loading in the context of the standing position above it. If your consultations regularly consider that connection, the second channel earns its place.<\/p>\n

How often should the plate be calibrated?<\/h3>\n

Ask the supplier for the interval they specify and the procedure they use, and follow it. Calibration is not a one-off event, because sensing materials age and drift. A system whose calibration history is unrecorded will eventually produce comparisons that are not comparisons.<\/p>\n

Can we see a demonstration before buying?<\/h3>\n

Yes, and we recommend running it on a real client rather than a member of staff who knows how to stand. Ask to see the ordinary report rather than the most dramatic screen the software can produce, and ask what the repeatability is between two captures.<\/p>\n<\/div>\n

What we would do next<\/h2>\n

If you want to see how the chain described above looks in practice, the F2Pro page<\/a> covers a system built for standing and walking captures, and the X3 page<\/a> covers a smaller configuration for a single room. For the reading side, our guide to reading a plantar pressure map<\/a> takes the conventions above and shows what they mean on a printed report. If you would rather start from your own workflow, send us the shape of your consultation<\/a> and we will tell you which channel you actually need.<\/p>\n

This article is intended for professional and educational reference. It is not medical advice. Foot assessment equipment produces measurements and images; clinical interpretation and any decision about care remain the responsibility of a qualified professional. Certification scope is limited to the documentation we hold: European Union certification and ISO quality system certification.<\/em><\/p>\n

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Related reading<\/h2>\n