🎯 Video Tracker — Physics Analysis

Overview

The workflow has four ordered phases. The toolbar mode buttons guide you through them left to right:

Results appear in real time on the right panel: an X(t) graph (red), a Y(t) graph (blue), and a data table. When you are done, export everything as CSV.

1 Load a video

Two ways to open a video file:

• Drag & drop the file anywhere onto the dark video panel.
• Click 📂 Load in the bottom controls bar and pick a file.

Set the frame rate (FPS)

The app defaults to 30 fps. If your video was recorded at a different rate (e.g. 60 fps slow-motion, 120 fps high-speed), change the FPS field in the bottom bar before you start tracking so that time values are correct.

Rotate the video (optional)

If the video was recorded in portrait mode, use ↺ 90° or 90° ↻ to rotate it without affecting the analysis.

2 Set up the coordinate origin

After loading a video the app is in ⚙ Origin mode. A white dot with red/blue dashed axes appears on the video.

1. Drag the white dot to the point you want to be (0, 0) in your coordinate system — for example, the launch point of a projectile or a corner of a table.
2. Optionally tilt the axes using the Axis° slider (or type an angle) in the top toolbar. This is useful when the surface of motion is not horizontal.
3. The red dashed line is the X axis; the blue dashed line is the Y axis (pointing up by default).

3 Calibrate the scale

Calibration converts pixels to real-world units (metres or centimetres). You need a known length visible in the video — a ruler, a metre stick, the length of a table, etc.

1. Click 📏 Calibrate in the top toolbar. The status bar changes to "Calibration — click 2 points".
2. Click the two ends of the known length on the video. Gold markers (labelled 1 and 2) appear, connected by a dashed line showing the pixel distance.
3. A dialog asks for the real-world distance between those two points. Enter the value and select the unit (m or cm) in the top toolbar, then click Confirm.
4. The status bar now shows "Scale: X.XX px/m" — calibration is complete.

You can toggle the gold calibration markers on/off with the Cal button in the top toolbar.

4 Track the object

Click 🎯 Track to enter tracking mode.

1. Navigate to the first frame where you want to start using the scrubber or ← / → arrow keys.
2. Click on the object in the video. A gold dot is placed and the video automatically advances by the number of frames set in the Step field (default: 1 frame).
3. Click on the object again in the new frame. Repeat until you reach the last frame of interest.
4. The graphs on the right update after every click.

Step size

The Step field (bottom bar) controls how many frames the video skips after each click. Setting Step = 2 halves the number of clicks needed and effectively samples the motion every 2 frames.

Correcting mistakes

• ↶ Undo removes the last tracked point.
• The ✕ button in the data table deletes any individual point.
• 🗑 Clear removes all points and resets calibration (asks for confirmation).

5 Graphs & curve fitting

The right panel shows two live graphs and a data table:

• X(t) — horizontal position vs. time
• Y(t) — vertical position vs. time

Curve fitting

Each graph has a dropdown to overlay a best-fit curve:

Fit coefficients are printed directly on the graph in yellow. For a quadratic Y(t), the a(t²) coefficient equals ½g — compare it with −4.9 m/s² to check your calibration.

Showing / hiding graphs

Use the checkboxes in the graph headers to show or hide individual graphs. When a graph is hidden, its column is also hidden from the data table.

6 Export data (CSV)

1. Click ⬇ CSV in the top toolbar.
2. A dialog lets you choose which columns to include: Frame #, Time (s), X position, Y position.
3. Click Export. The file tracking_data.csv is downloaded immediately.

The CSV is ready to open in Excel, Google Sheets, Python (pandas), Logger Pro, or any data-analysis software.

Video controls reference

Tips & tricks

Getting accurate results

• Use a slow-motion video (60–240 fps) for fast events like a bouncing ball; set FPS accordingly before loading.
• Keep the camera still during recording. Panning adds a systematic offset to all positions.
• Place the calibration object in the same plane as the motion; otherwise perspective introduces a scale error.
• Use trim points to restrict the scrubber range to only the frames of interest — this makes stepping through faster.

Typical physics experiments

Keyboard shortcuts

Shortcuts are disabled while the cursor is inside a text or number input field.