Open Gnomon →
Optical contour inspection

Automated dimensional inspection from the camera you already have.

Sketch or import the part, set its tolerances, put a part under the camera. Pass or fail in a second — every dimension measured, every edge compared with the drawing, and a report you can sign.

⌀10.009 tolerance ⌀10.00 ± 0.05 → PASS
Open Gnomon →How it works

Runs in your browser. Images never leave your computer.

A part under the camera: the hole is 0.31 mm too large, the check fails, every rule listed with its measured value and tolerance
How it works

Four steps, no specialist needed.

Set up

A webcam on a stand, looking down at a backlit table. A tablet shows the calibration board: scale, perspective and lens are measured in a minute.

Sketch

Draw the part like a CAD sketch, write it as a script, import the DXF — or teach it from a good part. Set the tolerances: ISO 2768 in one click.

Check

Put a part down. Gnomon finds it in any position, fits the drawing, measures every edge and dimension. Press Space: pass or fail, logged.

Report

A report per part with the picture, the deviations and every check — print or PDF. History and yield, exported to CSV.

Features

Everything between the drawing and the verdict.

A real sketcher — and a script

The sketch and its script are one and the same: draw with the tools and the script writes itself; type in the script and the drawing follows.

  • Lines, arcs, circles, slots, polygons, fillets; relations (parallel, tangent, concentric …) and driving dimensions, like a SolidWorks sketch
  • Type a value on any element — length, radius, angle — and the number in the script changes
  • Blue is still free, white fully defined; conflicts show in red
  • Variables (W = 60) and expressions in every dimension
The sketcher: a plate with two holes, fully defined, with its script on the left

TurtleCAD scripting

Describe a contour the way you would walk it. Every number is a dimension you can edit later from the drawing.

# rounded plate, 60 x 40, R5 corners
moveto(-25, -20)
for i in range(2):
    draw(50)
    arc(5, 90)
    draw(30)
    arc(5, 90)
A = circle(15, 0, 10)
A turtle script and the contour it draws, with the turtle at the cursor line

Checks in plain words

Every element has signals — length, radius, centre, direction, straightness, roundness. A check is one line:

A.diameter ± 0.05
plate.top.length iso
perpendicular(plate.bottom, plate.right) < 0.05
position(A) < 0.2
  • Suggested from the drawing: every dimension, every hole, size and position
  • ISO 2768-1 and -2 general tolerances (f, m, c, v · H, K, L)
  • The whole contour is also checked against a tolerance band: burrs, missing material, extra holes
A part in any position, fitted to the drawing and passing

Measure, annotate, report

  • Measuring tools that snap to the sub-pixel edge: circle, radius, edge line with straightness, edge-to-edge distance with parallelism, angles
  • Measurements follow every next part, in whatever position it lies
  • Arrows, rings and notes for the report
  • A4 report per part, history with pictures, yield, CSV export
Measuring a hole on the edge, with the magnifier showing the sub-pixel edge

Calibrate with a tablet

The board page turns a phone, tablet or monitor into a calibration target, sized from the screen's pixel density and checked with a bank card. It measures scale and perspective, the lens distortion, and even the edge offset of your camera and light.

The calibration board page with its size verification

Reports you can sign

The picture with the deviations, contour statistics, holes and radii, every check with nominal, measured value and tolerance, notes, calibration and signature lines.

An inspection report
Precision

Honest about what it can measure.

Sub-pixel edges, a calibrated plane, a corrected lens and a corrected edge offset. And for every check, Gnomon tells you whether your setup can actually judge that tolerance.

⌀10.009
measured on ⌀10.000 (synthetic test, 8 px/mm)
59.999
corner to corner on 60.000 mm
0.5 s
a full check of a 16-megapixel frame
Cg · Cgk
built-in repeatability study

Uncertainty budget

From pixel size, edge repeatability, calibration residual and lens: the uncertainty of every measurement, and the smallest tolerance judged reliably.

Traffic light per check

Tolerance against uncertainty (TUR) on every rule: green is judged well, amber is marginal, red is too tight for this setup.

Repeatability study

Measure the same part a number of times — placed again or not — and get the spread and Cg / Cgk per check.

Why Gnomon

Products fail on the basics.

Most products that fail in the market do not fail for exotic reasons. They fail on the basics of engineering: a hole 0.3 mm too large, an edge out of square, a forgotten radius, a supplier batch that slowly drifted out of tolerance.

Measuring catches these. But coordinate measuring machines and industrial vision systems are expensive, slow to set up and need a specialist — so in many small and mid-sized companies a few parts are checked with a caliper, or none at all.

Gnomon removes the entry barrier: the camera you already have, a tablet as calibration board, a drawing with its tolerances — and every part checked in a second.

The name

γνώμων — “the one who knows”

In Greek the gnomon was the carpenter's square that checks a right angle, and the blade of a sundial that tells the truth from a shadow.

Gnomon does the same: it reads a part from its silhouette and checks it against the drawing.

For

Quality departments in small and mid-sized manufacturing: incoming inspection, first articles, spot checks.

Parts

Flat parts and profiles: sheet metal, laser and waterjet cut, stamped, gaskets, machined plates, 3D-printed.

Check your first part today.

Open Gnomon in Chrome or Edge, with a webcam and a tablet or phone for the calibration board.

Open Gnomon →Calibration board
TitleGnomon — optical contour inspection
StandardISO 2768 · ISO 3098
Scale1 : 1
Sheet1 / 1