Recommended test
Calibrate a simple image with a known length, trace one rectangle and verify the resulting size.
- Open Grid mode and add a PNG, JPEG or WebP image smaller than the stated upload limits.
- Pick two visible calibration points and enter their known real-world distance.
- Lower image opacity, trace a simple closed rectangle, and hide the image.
- Push/Pull the region and use Tape Measure to confirm the calibrated dimension.
Load a usable reference
Grid sketch accepts PNG, JPEG and WebP images. The current UI limits a file to 10 MB and about 40 million pixels. Crop the image to the relevant object and use a view with minimal perspective distortion.
Calibrate from two points
Choose two points whose real distance is known, then enter that distance. A long, reliable reference reduces proportional error. A photographed ruler at an angle is less useful than a documented overall dimension on a straight elevation.
Trace with restraint
Adjust opacity so both the image and sketch remain readable. Use lines for straight segments and arcs or splines only where they are necessary. The default image scale and opacity are starting conveniences, not dimensional evidence.
Verify independently
Hide the reference image and inspect the sketch alone. Confirm closure, remove accidental short segments and extrude a shallow test. Measure at least one second known dimension: matching only the calibration line does not prove the image itself is undistorted.