LiDAR points per roof face calculator

LiDAR points per roof face

Synthetic model: points scattered at random, Gaussian vertical noise, least-squares plane. A design aid, not a survey result.

Units

Point density (per m²)

Run, up the slope in plan (m)

Width along ridge (m)

Pitch (rise per 12 of run)

Vertical noise, one SD (cm)

-Plan area

-Sloped (true) area

-Expected points on the face

-Mean point spacing

-Pitch error, one SD (degrees)

-About 95% of fits within (degrees)

-Sloped-area change per 1 degree pitch error

Roof object (vent, chimney, hatch)

Object length (m)

Object width (m)

-Expected points on the object (plan area x density)

-Chance of 1 or more points

-Chance of 3 or more points

Formula: one-SD slope error = noise x sqrt(12) / (run x sqrt(points)); pitch error = slope error / (1 + slope squared). Below about 20 points the figure is a lower bound: in our 4,000-trial runs the true spread was 1.1 times larger at 15 points and 2.3 times at 4 points. Density is per area seen from above, as airborne data is quoted. Vertical walls get no points. Check the dataset's own pulse or point density and year.