Flagstone layout from one tarp photo

01 The tarp protocol

Five steps on the ground before the photo

Roman road builders sorted polygonal basalt by eye before they laid it. The tarp is the sorting floor, and the photo is the sorting done once.

1. A plain tarp, pulled flatBlue or grey, no folds, no print. The tarp color is read from a strip along the photo's edge, so the stones must differ from it in brightness or color.
2. Stones apart, face up, clear of the edgeA stone that touches another reads as one stone. A stone cut by the frame is dropped and listed in the placements file, never silently lost.
3. The scale card beside the stonesA white or bright card, 12 by 8 inches unless you say otherwise, flat on the tarp and touching no stone. The card sets the scale for every stone in the photo.
4. One overhead photoCamera level and square to the tarp, at midday under open sky or in even shade. A hard shadow reads as stone.
5. Chalk the numbers after the first runWrite each stone's number on it from the numbered photo, so the plan and the pile match in seconds.

02 What comes back

Three files, every number computed from your photo

• Layout mapThe outline with every placed stone numbered, and a legend that points each number at its box in your photo.
• Numbered photoYour photo with the same numbers on the stones.
• Placements fileScale, every stone's area, every placement (position, turn, face up or down), the void ratio, the narrowest joint, the overlap check and the stones that found no spot.
• Void ratioOne minus the covered area over the outline area. It counts joints and every gap. Lower is tighter.
• JointThe clear distance kept between any two stones, half an inch unless you set it. The narrowest joint is reported.
• Overlap checkThe summed intersection area between placed stones, which must read as zero. The run says PASS or FAIL.
• Unplaced stonesListed by number, never dropped. A layout that needs a cut stone is a different job.

[TIER: COMPUTED] means the output of the tool from its inputs, and nothing more. A tape measure on three stones, with the date and a photo, lifts the layout to MEASURED. The tool produces no CERTIFIED figure.

03 What the layout is not

Where the tool stops

• Top layer only. The tool reads the face of each stone from above and nothing below it.
• Two dimensions. Thickness, edge bevel, rocking and the setting bed are outside the model. No stability claim is made.
• No cutting. The fit is found with the stones as they are.
• The scale rests on a flat card on a flat tarp. Tilt, lens distortion and a curled card bend it.
• Shadows, folds and printed tarps read as stone; touching stones read as one.
• The fill is a heuristic: a tight layout, not a proof of the tightest one.

A retaining wall of the same stones, a pool edge or a fence inside the five-foot zone each take their own permit path. Read it on the code triage sheet before a number reaches a client.

04 Request a layout

Send the outline now, the photo by reply