Satellite roof measurement: a contractor's complete guide

Satellite roof measurement is the practice of estimating a roof's area, perimeter, pitch, and complexity from aerial imagery — without sending an estimator to the property. Done right, it cuts your cost per estimate from $80–$120 down to $1–$3. Done badly, it produces guesses you can't bid against. Here's how it actually works, what's achievable today, and where it falls short.

The three data sources

Every satellite roof tool combines two or three of:

• High-resolution aerial imagery — usually licensed from EagleView, Nearmap, or Esri World Imagery. Resolution ranges from 30 cm/pixel (free Esri) down to 3–7 cm/pixel (paid EagleView/Nearmap).
• OpenStreetMap building footprints — community-traced building outlines available globally for free. Coverage is ~85% in US urban / suburban areas, much lower in rural ones.
• Computer vision models — segmentation models like SAM 2 that detect rooflines from the imagery directly, for areas where OSM has no footprint.

How accuracy stacks up

The number that matters: how close is the satellite measurement to a tape-measure on-site reading?Across thousands of measured roofs:

• Simple gable on a typical lot: 3–5% off, almost always within 7%
• Complex multi-plane roof with valleys: 5–9% off (humans need to refine the polygon)
• Wraparound porch + dormers + bay windows: 8–14% off without refinement

The waste-factor question

Satellite measures plan area (the bird's-eye square footage). What you actually need to order is installed area: plan area × pitch multiplier × waste factor. A typical asphalt shingle install adds:

• 10–15% pitch multiplier for a 6/12 pitch (more for steeper)
• 10–15% waste factor for cuts, valleys, ridge cap
• For metal or tile: 5–8% waste factor (cleaner cut patterns)

When to still send someone out

• Decking is suspected to be rotten — you can't see that from space
• The home is rural / new construction with no OSM footprint AND no high-res imagery
• The customer is a high-value commercial / municipal job where the bid risk justifies the truck roll
• The quote is over $50K and the customer is comparing 3+ contractors

Cost math: aerial vs. drive-out

At a typical close rate of 25%, a contractor sending out 4 estimates per closed job spends $360 in estimating cost per win. Switching to aerial drops it to $13 per win. The bigger ROI: estimators can bid 5–10× more jobs per day from the office.