How satellite roof measurement works

Satellite roof measurement in RoofSell starts with the address a homeowner picks. The widget finds that building's outline, works out the roof slope, and turns both into a roof area and a price for each product you sell. Nobody climbs a ladder, and the homeowner can adjust the result before submitting.

What the homeowner sees

  1. They type their address and pick it from the suggestions.
  2. The satellite map zooms to the property and outlines the roof. A detached garage or shed may get its own outline.
  3. The slope of the main roof is filled in when it can be detected. They confirm it or pick Shallow, Medium or Steep, plus Flat if you sell flat roof products.
  4. If the outline is off, they click Edit Roof and drag the corners, or Add Roof to draw another structure.
  5. They enter their contact details and see a price for each product you selected.

Where the satellite roof measurement comes from

  • Building outline. RoofSell looks up the building footprint in OpenStreetMap data, matched to the street address, with a public US building footprint dataset as a backup.
  • Size check. The outline is compared with Google's Solar API measurement for the same spot. If the sizes are far apart, which happens when map data lumps several buildings together, RoofSell rejects the outline.
  • Slope. Google's Solar API reports the pitch of each roof section. RoofSell takes a weighted average and files it under the nearest slope category.
  • Imagery. The map shows Google satellite imagery when it's available, and Mapbox imagery otherwise.

How the outline becomes roof area and a price

The outline gives the footprint, the flat area the building covers. RoofSell then adjusts it for slope:

  • Roof area, shown as Total SqFt on your Dashboard, is the footprint times a slope factor: 1.000 for Flat, 1.031 for Shallow (3/12), 1.158 for Medium (7/12) and 1.302 for Steep (10/12).
  • Price starts from the footprint, adds your waste factor and the slope markup shown in Settings under Slope Pricing, converts the result to squares (100 sq ft each) and multiplies by each product's price per square.

Homeowners see prices, not square footage. You see the full numbers on the Dashboard, in the new lead email and on the quote page.

For the longer story, read how satellite roof detection works. To know when to double-check a number, see roof measurement accuracy.

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