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How accurate are satellite roof measurements?
The honest answer is that it depends on what made the number. A building footprint traced from overhead imagery is one thing. A roof analysis from LiDAR is another. Only one of them is a measurement you should price from.
What you will do
- Know what the imagery can prove
- Spot the cases that need a field check
- Price from a number you trust
What the imagery can and cannot see
A footprint is a ground plan, not a roof. A public footprint data set is the shape of the building, traced from a photo. They do not describe roof planes, so eave overhangs, dormers, and multi-plane geometry are simply not in the data. Treating a footprint as a roof area will understate or overstate every job with an overhang.
The imagery has an age, and it is not today. Footprints in the national dataset come from imagery roughly 2019 to 2023, depending on the county. A structure built or re-roofed after that capture will not match what you are looking at. An addition will be missing entirely.
Small structures may not be present at all. The national data set only holds buildings over about 450 square feet. A garage can be missing. So can a shed, or a small add-on. Nothing tells you it is gone.
Height data is frequently missing. Where a dataset does carry a height attribute it is often null, so pitch cannot be inferred from it. Pitch has to come from a source that actually measures elevation, or from a person on the roof.
How to judge a measurement before you price from it
- 1
Ask what produced the geometry
A traced footprint is not as sure as a LiDAR surface. Neither is as sure as a takeoff you draw by hand. If a report does not say which one it is, that is your answer about how far to trust it.
- 2
Confirm the building is the right building
The first failure mode is not accuracy, it is identity: the wrong structure on a multi-building parcel. Confirm the outline sits on the roof you are quoting before you read a single number.
- 3
Check the vintage against the property
A footprint comes from imagery that is usually a few years old, and how old varies by county. A small structure under about 450 square feet may not be there at all. A recent addition or re-roof will not be in the data.
- 4
Treat pitch and waste as separate questions
Area from overhead is the easy part. Pitch, layers, penetrations, and waste factor are where estimates go wrong, and none of them are visible in a plan view. Height attributes in public datasets are frequently null, so pitch cannot be inferred from them.
- 5
Get on the roof when the money justifies it
An aerial number is a fast, defensible starting point for a quote. It is not a substitute for a field check on a complex or high-value roof, and any tool that tells you otherwise is selling you something.
How FL Permit Pay handles this
- FL Permit Pay starts a roof outline from public building-footprint data. It treats that as a starting point you can edit, never as a measurement of record. The shape is yours to correct. A correction is recorded with where the number came from, and it does not overwrite the original report.
- A measured job and a footprint guess get different labels. We do that on purpose. A figure that came from a footprint is shown as an estimate. Where it feeds a proposal, that draft is labeled too, and a person has to read it before it can go out.
- A guard stops an old or unlikely surface being stamped as measured. The danger is not a wrong number. It is a wrong number wearing a confident label.
- The field check is the contractor's call and the contractor's job. FL Permit Pay does not certify a roof it has not touched.
Common questions
How accurate are satellite roof measurements?
It depends on the source. A roof analysis built from elevation data can be close enough to quote from on a simple roof. A building footprint traced from overhead imagery is a ground plan. It does not describe roof planes at all. Accuracy also drops as the imagery ages, as the roof gets complex, and with anything built after the capture date.
Can I price a job from an aerial measurement alone?
For a simple roof with recent imagery and a confirmed building, an aerial number is a reasonable basis for a quote. For complex geometry, multiple layers, or a high-value job, treat it as a starting point and verify in the field. The measurement tells you area and lines; it does not tell you what is under the shingles.
Why does the outline not match the roof edge?
Because a building footprint follows the structure's ground plan, not the roof. Eave overhangs sit outside the footprint, and multi-plane roofs are flattened to a single outline. That is why the outline has to be editable rather than authoritative.
What if the house was re-roofed or extended recently?
The imagery will not show it. Each county was captured on its own date, and most are a few years old. Anything built or torn down since then is not in the data. Confirm the current condition with the homeowner or in person.
Put the guide to work.
Start from an aerial outline you can correct. Keep the correction on the record. Then price from a number you can say where it came from.