How to set scale on a scanned plan
A scanned print is usually a reduced copy, so the scale in the title block no longer holds. Trace one dimension you can read on the sheet, type what it really measures, and every length after that is right.
Step by step
- Step 1Upload the plan set and open the sheet you're biddingUpload the PDF as it came to you, scan and all. Open the sheet that carries the work you are pricing — the one with a dimension string you can read.
- Step 2Find a dimension you can read on the sheetA dimension string, a door width, a column grid spacing. Anything printed on the drawing whose real length you can trust. A grid line spacing is usually the safest on a poor scan.
- Step 3Trace that dimension with the calibrate toolClick one end of the dimension and then the other. Draw along the printed line, not across the label.
- Step 4Type the real-world lengthEnter what the drawing says that distance is, in feet and inches. FastBid works out the ratio between screen distance and real distance from that single trace.
- Step 5Check it against a second dimensionMeasure another known distance on the same sheet. If it reads back correctly, the sheet is calibrated. If it is off, retrace the first dimension more carefully.
- Step 6Calibrate each sheet you measure onScale is stored per sheet, because sheets in one set are often printed or scanned at different reductions. Counts do not need scale; only lengths and areas do.
The questions that follow
Why can't you trust the scale printed on a scanned plan?
Because a scan is a copy of a print, and prints get reduced. A set drawn at 1/4 inch to the foot and printed on 11x17 from a 24x36 original is no longer at that scale, even though the note in the title block still says so. Tracing a known dimension measures the sheet as it actually is.
What if there is no dimension on the sheet?
Use the column grid. Grid spacing is called out on the structural or floor plan and holds across the set. Failing that, use a standard door leaf at 3 feet, then verify against a second opening before you rely on it.
Does calibration change counts you already made?
No. Counts are markers, not measurements, so they stay as they are. Lengths and areas recalculate from the new ratio, so re-check any run you measured before calibrating.
How accurate is tracing by hand?
Within a fraction of a percent when you trace a long dimension. Pick the longest known distance on the sheet rather than a short one — error in the trace is spread over more feet, so it matters less.
Related
Run one real bid through it.
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