Complete overview of the features, shown for Science mode, together with the limits of the app in classroom use. It complements the student handout – it does not replace it. As of program version 95. · Deutsche Fassung
| Check the version | At the bottom of the start screen: Version 95. If a device shows a lower number, an old version is still active there – reload the page once. If the line adds “version … ready – reload the page”, a newer version has already been downloaded but is not running yet. Different versions within one class lead to “on my screen it looks different”. |
| Device test | On the actual school computer, load a video once and run a short tracking pass in Science mode. That loads the ~5 MB template-matching module (and on a PC the ~19 MB AI guard) once; after that they are available offline. |
| PC link | Never test it for the first time during the lesson. On managed school computers it often fails – the reasons and the alternative are in section 9. |
| Recording rules | Tell the class: 1080p, 30 frames per second, no more than 30 seconds, camera steady and perpendicular to the plane of motion, a reference object (meter stick) in exactly that plane and in shot. iPhone: Camera → Formats → Most Compatible. |
| Reference lengths | Decide them in advance and write them on the board – the app offers no list of standard lengths to choose from; you type the number in. |
| Handing in work | Decide how results are collected (learning platform, network drive, USB stick). The app itself cannot send anything. |
Choosing the mode on the start screen is the only decision you have to make. It can be changed at any time via ⚙ → Mode; all data is kept. Switching Science → Student only hides objects 2 and 3 and the advanced tools, it deletes nothing.
| Student mode | Science mode (this handout) |
|---|---|
| Load video, frame by frame, limit clip range, track one object,
manual point correction, scale, move the origin, s(t) and v(t), path points,
CSV export.
Axes: only t, s, x, y, v.
After the mode has been chosen, a short guide is offered: a speech bubble walks through loading the video, the playback buttons, clip range, axes and marking up to tracking, axis choice and scale, with “Next” and “Back”; completed steps advance on their own. |
In addition: a(t), all quantities as x/y components, momentum p, force F = m·a,
energies, mass per object, rotating the axes, adjustable g, vector arrows,
stacked view, area calculation, model fits, strobe image, center-of-mass curve,
up to 3 objects, JSON export.
No guide – hence this handout. |
Mode badge · status bar · Open project / Save project / Export · Pair · Settings. The status bar is your most important monitoring tool: it shows the time, the frame number, the frame rate actually in use and – only once you have calibrated – the scale in px/m. If the px/m figure is missing, the app is calculating in pixels.
The default is stacked (video on top, chart below). Two columns side by side appear only from about 900 × 480 pixels – that is on a PC and on a tablet, not on a phone. On a PC the boundary can be dragged freely between 20 % and 80 % with the splitter. The bottom bar holds the clip handles, the timeline, ⏮ ◀ ⏵ ▶ (⏮ jumps to the start of the chosen clip – which is also where t = 0 sits) and Load video.
px.
| Control | What it does | Requires |
|---|---|---|
| Object 1 (24) ▾ | Opens the list of all objects; a click makes one of them the active object. The number in brackets is the number of data points. Almost every tool refers to the active object. | from 2 objects or data points onwards |
| 🗑 in the object list | Deletes the data points of this object after a confirmation prompt. The region is kept – you can re-track right away. | object has points |
| Mark object | Marking mode; dragging a box in the video defines the search region. | video, no tracking running |
| Start tracking | Frame-by-frame run over the limited clip range. Deletes this object's existing points without asking. | region set |
| Set scale | Two-point calibration, then you enter the real length. | video |
| Set mass (reads “Mass: 145 g”) | Mass of the active object. The basis for p, F, Eₖ, Eₚ, Eₘ and the center-of-mass curve. | Science mode |
| Track 2nd / 3rd object | Creates another object (turquoise, raspberry) and makes it active. Three at most; objects once created cannot be removed again (only their points). | Science mode |
| Control | What it does | Requires |
|---|---|---|
| Coordinate system | Axes on/off. While hidden, they are also protected against being moved. | video |
| Path | All tracked positions as an evenly spaced trace of dots – shows the shape of the trajectory (projectile parabola, circle). | data points |
| Trail | Only the last 8 positions, fading out – emphasises the motion at this instant. | data points |
| Show vectors | Dialog with checkboxes for s (position vector), v, a, p, F – each with its own length slider (0.1× to 10×).
Below that, three settings that apply to all arrows at once: Symbols on the arrows labels every arrow with s, v, a, p or F (on by default; switch it off when many arrows on several objects clutter the image – the size slider is then greyed out), Size of the symbols 14–48 px (default 20) and Arrow thickness 1–5 as a factor on the automatic base width. All three are remembered – for the projector, setting them once is enough. | Science mode; p and F only with a mass |
| Center of mass | ⊕ in the video with a connecting line, plus a dashed curve in the chart. In a collision this is the didactic core: the center of mass moves on undisturbed. | ≥ 2 objects with mass and points |
| Mirror | Swaps left and right in the image so that a motion running to the left gives positive x values. The rotation of the axes is not mirrored along with it – on an inclined plane, realign them afterwards. | video, no tracking |
| Control | What it does | Requires |
|---|---|---|
| Lines | Connects the data points. Off by default: measured values are points, the trend comes as a model curve. | – |
| Time line | Vertical cursor line through the chart. Off by default – useful only when t is on the x axis. | – |
| Stack (+ count) | 1–3 compact charts one above the other, preset to x, vₓ, aₓ over t, with derivative arrows in between. | Science mode |
| Chart range | Type in the axis limits by hand (min/max per axis) – for axes that stay comparable across several groups and for clean diagrams for the board. Automatic resets it. | Science mode |
| Area | Area mode: dragging in the chart selects a range (section 6.1). | Science mode |
| Model | Choice of no model / linear / quadratic / oscillation / damped oscillation (section 6.2). | Science mode |
| Control | What it does |
|---|---|
| Axis selectors v in m/s t in s | Choice of quantity for y (top left) and x (bottom right). The two axes can be combined freely – including y over x (the trajectory) or Fₓ over x. The label also shows the unit: if it reads px, the scale is missing. |
| Selectable quantities | t · s · x · y · v · vₓ · vᵧ · a · aₓ · aᵧ · F · Fₓ · Fᵧ · p · pₓ · pᵧ · E (three curves) · Eₖ · Eₚ · Eₘ |
| Legend | Appears from two curves on. A click hides a series – that state is kept (even after the clip range is changed). Important: area and fit apply to the first visible series. |
| Red marker | Marks the current frame on every visible curve. A click on a data point jumps the video there. |
| Readout box | Top right: the numerical values of the quantities currently plotted, for the current frame, each object in its own color. |
| Zoom / pan | Mouse wheel or two fingers; dragging pans. A double click restores the automatic fit. In area mode, dragging means “select a range” instead. |
Only Language, Smoothing and Mode are visible; everything else sits collapsed under Advanced settings – expanding it reveals the remaining rows of this table, including Measure playback (a diagnostic card that counts drawn, expected and presented frames during playback – useful when a device stutters).
| Language | DE / EN, takes effect immediately; units and symbols stay unchanged. |
| Display size (projector) | Presentation mode: 100 % / 125 % / 150 % enlarge all text – controls, chart axes, data table. The table then shows correspondingly less, but with larger rows. The choice is remembered and applies again at the next start.
Why by hand? The browser knows the resolution of the output device, but neither its physical size nor the viewing distance – a projector reports the same as a monitor. So the level has to be set; on a student's device 100 % remains sensible. |
| Frame rate | automatic / 24 / 25 / 30 / 50 / 60 / 120. The most important lever for corrections – see section 7.1. |
| Mode | Student / Science, the data are kept. |
| Gravity g | Default 9.81 m/s². g is not measured, it is set – the value enters Eₚ = m·g·h only (and thereby Emech). Distance, velocity, acceleration, momentum, force and Ekin come entirely from the video and do not change with it.
So why change it at all? First, for videos that do not take place on Earth (Moon 1.62 m/s², Mars 3.71 m/s²) – the hammer-and-feather demonstration of Apollo 15, for example. Second, as a check exercise: the class reads a off a free-fall measurement or fits it, enters that measured value here and tests whether Emech then stays more nearly constant than with 9.81 – which brings home that what sits here is an assumption, not a measurement. Third, for location-specific work (g varies between 9.78 and 9.83 m/s²), though in school measurements that difference vanishes into the noise. |
| Accuracy over speed | Makes the tracker seek exactly to every frame during the run instead of letting the video run through. That takes longer, but delivers the same data points on every device – without the checkbox, the speed of the computer has a say in how precisely the points sit. Off by default; the choice is remembered. Whether it took effect is shown by the balance after the run (“read while playing 0”). |
| Smoothing | Four steps 3 / 5 / 7 / 9 (default 5): over how many data points the values are averaged before differentiating. Applies to all objects at once, and the analysis is recalculated immediately. The hint below states the corresponding time span in ms for the current frame rate – at 30 frames per second that is 100 / 167 / 233 / 300 ms. Larger windows calm v and a, but flatten short events (section 7.2). |
| Version, Legal notice | Program version and the legally required publisher details together with the privacy statement. |
→ Area, then drag across the range you want in the chart. The result box gives the value, the unit, the object concerned, the physical meaning and the range. The meaning depends on both axes:
| Chart | Area means | Unit |
|---|---|---|
| v(t), vₓ(t), vᵧ(t) | distance traveled Δs – with a direct cross-check from s(t) | m |
| a(t), aₓ(t), aᵧ(t) | change in velocity Δv | m/s |
| Fₓ(t), Fᵧ(t) | impulse = momentum change Δpₓ or Δpᵧ | kg·m/s |
| Fₓ(x), Fᵧ(y) | work Wₓ = ∫Fₓ dx (stretches traveled back count as negative) | J |
| F(s) | the work done, but only if the force acts along the path – otherwise a warning | J |
| anything else | no value, but a note on which combinations are meaningful | – |
Once a model has been chosen, sliders appear below the chart with rough starting values taken from the data – deliberately not the finished fit. The class brings the curve into line by hand, watching R² update live as they go. Auto-fit then computes the best solution and shows how close they got. Back to video only folds the sliders away; the curve and its parameters remain.
Replaces the single chart with up to three charts on top of each other, with derivative arrows in between (vₓ = dx/dt, aₓ = dvₓ/dt, v = ds/dt). The arrows deliberately appear only where the relation holds exactly: for the components and for the arc length. There is none between v and a – that is no oversight but the pointer to |a| ≠ d|v|/dt. The view shows only one object and offers neither area calculation nor fitting. On a phone the stacked view hides the video and uses the whole display area – otherwise each chart would be only a few centimeters tall; Mark object or Set scale bring the image back. On a PC the stack sits next to the video as usual.
All calculated quantities of the active object as a table of numbers, row by row; the row of the current frame is highlighted, and tapping it jumps the video there. Columns in Science mode: t, x, y, s, h, vₓ, vᵧ, v, aₓ, aᵧ, a, F, Fₓ, Fᵧ, p, pₓ, pᵧ, Eₖ, Eₚ, Eₘ – the ones that depend on the mass and on the scale appear only when those prerequisites are met. In Student mode there are five columns (t, x, y, s, v).
In the menu → group “Results” there are two buttons for this; both exist in both modes:
| View | Layout | What for |
|---|---|---|
| Table + video | The table takes the place of the chart: on a PC video on the left, table on the right; on a phone video on top, table below. | Check measured values against the image – tap an odd-looking row and the video jumps there and shows what happened at that point. |
| Table + chart | The video gives way (as in fit mode): on a PC chart on the left, table on the right; on a phone chart on top, table below. | From the chart to the number and back – reading off values, copying them into the exercise book, spotting outliers. |
Pressing the same button again closes the table; the other one switches the layout. The stacked view and the fit sliders claim the same space – they therefore switch the table off (and vice versa). The red marker, the highlighted table row and the video frame stay in sync in every view.
Set the split yourself. Between chart and table sits a splitter (vertical on a PC, horizontal on a phone). It divides the space freely between 15 % and 85 % – important in Science mode, where up to 19 columns sit side by side and you want to see them at the same time. A double click on the splitter restores the default. In the “Table + video” view this job is taken over by the splitter that already sits between the video and chart columns.
Combines 3 to 30 tracked frames into one picture – for the strobe image the cut-outs of the object are copied into the base frame, for the strip image vertical slices in time order are lined up next to each other. Optionally with the measured points drawn in. The PNG export delivers the full video resolution and suits worksheets on which students measure with a ruler.
| CSV | One file per object. Switch between “German (Excel)” (semicolon, decimal comma) and “International”. What is exported are the smoothed analysis values of the selected clip range in the current coordinate system – exactly what the charts show. |
| JSON | A full dump of the app state including the raw points. Science mode only. Cannot be imported back. |
| .wod project | Video and analysis in one file – the way to hand work in and to pass on ready-made examples. As large as the video.
On saving, Chrome and Edge open the system dialog: folder and name are yours to choose, straight onto a network drive if you like. Cancelling saves nothing, and no substitute download appears either. In Firefox and on iOS the app only asks for the file name, and the file then goes to the downloads folder. CSV and JSON still download immediately, without asking. |
| Missing / limited | What it means for teaching |
|---|---|
| No chart export as an image | Neither the chart nor the stacked view nor the table can be saved (only the strobe image, as a PNG). Use screenshots for worksheets – set round axis limits via Chart range beforehand. |
| Fit parameters and area values are not exported | R², model parameters and area results appear on screen only. They belong in the lab write-up – that is pedagogically defensible, but you have to tell the class. |
| The center-of-mass curve is not exported anywhere | For a collision experiment, export the individual objects and work out the center of mass yourself in a spreadsheet. |
| No JSON import | For backups and for passing work on, always use Save project (.wod). |
| Individual points cannot be deleted | Drag stray points to the plausible position; if a whole section is unusable, set the clip range more tightly and track again. |
| Points placed by hand are always green | The color coding rates the automatic detection only. Corrected points therefore look more reliable than they are – say so in class. |
| Tracking again deletes the manual corrections | Order: track first, then correct. Save the project before making bigger corrections. |
| Only four model functions | Exponential growth, power laws or hyperbolas cannot be fitted. Tailor the questions accordingly. |
| At most three objects, not removable | Objects created by accident stay in the list (but are only a visual nuisance). |
| “Restart” (⚙, since version 95) | After a confirmation prompt it deletes the saved state and starts empty; the language choice is kept. On shared devices, introduce this as a ritual at the end of the lesson. |
| No search-radius or threshold slider | These values adapt automatically; contrary to older documents there is no way to set them. |
| One autosave state per device | The autosave is crash protection, not a filing system: it stores only the session last worked on, and never the video. For several analyses, create a separate .wod file for each one. |
| There is no lossless way back from the app to the start screen | Mode, Language and Legal notice are reachable via the gear icon; the student handout only from the start screen – so open it beforehand. (“Restart” does lead to the start screen, but discards the analysis.) |
The PC link transfers the video and the data points from the phone to a second screen: one device starts the session and shows a six-character code, the other types it in. The data travels directly between the devices; a small signaling server on the network only brokers the connection and never sees video or measurement data.
Observation: two browser windows on the same laptop link up without trouble – laptop and phone never find each other, not even on the phone's hotspot. The app's diagnostics (the browser console) showed:
How to read it: both devices had exchanged complete addresses (host = local address, srflx = public address), yet connection setup failed on every path. Firefox says so explicitly: “ICE failed, add a TURN server”.
Causes on managed machines – usually several at once:
Important: the first two points are down to the device, not the network – which is why switching to a phone hotspot does not help either.
What the app does: if no connection is established 20 seconds after the
code was exchanged, it says so in plain language, lists the likely causes and appends
the short candidate summary – for example [own addresses: host×2 srflx×1 · other side: host×2]. If
srflx is missing there, outbound traffic is blocked; if the other side is missing
entirely, the connection request never got through.
What the app deliberately does not do: it uses no relay (TURN). Such a detour would get past even strict firewalls, but it would route all payload data through someone else's server – which contradicts the principle that videos never leave the device. So if the devices cannot find each other directly, there is no fallback route.
What works in practice in the classroom: (1) on private devices and on a home network the PC link usually works. (2) On a school computer use the file route: save the project (.wod) or a CSV and pass it on – that always works and needs no network. (3) If you want the PC link to work permanently on the school network, you need your IT admins: an exception that allows the local addresses for exactly this one web address, and an inbound firewall rule for the browser, limited to the local subnet.
| Symptom | Cause and remedy |
|---|---|
| Values in px instead of m | Scale missing. Check the status bar (the px/m reading) and run Set scale. |
| Momentum, force or energy missing | Mass missing (with two objects, for both of them!). Energies additionally need the scale. |
| Chart stays empty | The selected quantity does not exist for this object – or the series has been hidden in the legend. Briefly switch to a quantity that has a legend and show the series again. |
| All velocities twice/half as large | Frame rate detected incorrectly. ⚙ → set the frame rate by hand. |
| Curve jumps at the start | Outlier in the first frame. Correct the point or let the clip range start later. |
| Tracking loses the object | Draw the box tighter and around a higher-contrast area; if need be, stick a colored dot on the object. Reduce motion blur with more light. |
| Video does not load | Codec (usually HEVC). Analyze it on the recording device or record it again in H.264. |
| A click in the chart no longer jumps to the frame | Area mode is active – switch Area off. |
| The axes keep slipping | Tap the lock 🔒 to close it. Do it again after every session restore and every time you open a project, because the locked state is not saved. |
| The devices can't find each other | Section 9.2 – and when in doubt fall back on the file route. |
| Experiment | Analysis in WODAnalysis |
|---|---|
| Free fall / vertical throw | y against t with a quadratic fit → g from the parameter a (y = a·t² + …, g = −2a). Cross-check: aᵧ in the chart, Eₖ + Eₚ = Eₘ ≈ constant. |
| Horizontal projectile motion | The trajectory as y against x (axes freely selectable), plus x against t (linear) and y against t (quadratic) – the independence of the components becomes directly visible. |
| Collision of two carts | Two objects with masses; pₓ of both carts, sum them by hand; show the center-of-mass curve – it moves on undisturbed through the collision. Area under Fₓ(t) = impulse, area under Fₓ(x) = work. |
| Mass–spring oscillator | x against t fitted with the oscillation model, or the damped oscillation model where there is damping; read off T, and from it the spring constant D = m·(2π/T)². Film at least two to three full periods. |
| Simple pendulum | As for the mass–spring oscillator; in addition the energy conversion Eₖ ↔ Eₚ with the lowest point as the origin. |
| Circular motion | Show the path points; the a vector points to the center. The textbook case for |a| ≠ dv/dt – see 7.3. |
| Inclined plane | Rotate the axes (x along the path) and lock them; aₓ constant. Note: Eₚ still measures the height vertically in the image – exactly as it should. |
WODAnalysis runs entirely in your students' browsers: no login, no upload, and after the first visit even without internet. This handout describes program version 95; the version shown on the start screen should match it. Please send feedback and bug reports with the version number and – for pairing problems – with the short candidate summary from the status bar.