Satellite, aerial and drone roof measurements: when each one wins
Satellite imagery covers almost any address, oblique aerials see walls and overhangs, and your own drone photo is current. Here is when each one is the right source.
Satellite imagery wins when you need a number fast for an address you haven't visited, oblique aerial photography wins when walls, eave heights and overhangs matter, and your own drone or phone photo wins when the roof has changed or the imagery is too old to trust. Know which before you build a bid on it.
Three ways to get a roof in front of you
Satellite imagery
A top-down picture of the roof, taken from orbit. Coverage is wide: almost any address you type has something to look at. Image quality and capture date vary by location, and you usually can't pick either.
Oblique aerial photography
Photos taken from aircraft at an angle, usually from several compass directions. Because the camera looks sideways, you see fascia, siding, eave heights, the number of stories and how far the overhang sticks out past the wall. They are flown in campaigns, so an area refreshes when it is on the schedule, and coverage thins away from populated areas.
Your own drone or phone photo
You or your crew take it, so it shows the roof as it is today. A drone shot straight down gives the cleanest plan view of the three. The catch: a photo has no built-in scale. You need one known length in the picture, like a garage door or a taped ridge, to turn pixels into feet.
Side by side
| Satellite imagery | Oblique aerial | Your drone or phone photo | |
|---|---|---|---|
| What it sees | The roof outline from above: facets, ridges, hips, valleys, penetrations | Walls, fascia, overhang depth, eave height, stories | Today's roof, at the detail your camera and altitude allow |
| What it misses | Pitch, anything under trees or deep shadow, lower roofs tucked under upper ones | Areas off the flight schedule; work done since the last flight | Scale until you calibrate; anything out of frame |
| How current | Varies by location, from months to years | Refreshed per flight campaign | The day you shoot it |
| Cost to you | Often bundled into measuring software; your desk time | Usually sold by subscription or per report | Drone or pole gear plus a site trip |
When satellite wins
A lead calls about a tear-off on a hip-and-gable ranch, you pull the address, trace the outline, slice it into facets, and you have area and edge lengths before you call back.
It's strongest on simple to moderately cut-up residential roofs with clear edges and little tree cover. It struggles with dark shingles in shadow where a valley disappears, and any roof where a big oak hides the back slope.
Pitch is the gap. A top-down picture doesn't show slope, so you supply it, and it matters:
- Plan area from the trace: 2,400 sq ft
- At 6/12 (pitch factor 1.118): 2,400 × 1.118 = 2,683 sq ft, about 26.8 squares
- At 8/12 (pitch factor 1.202): 2,400 × 1.202 = 2,885 sq ft, about 28.9 squares
Two pitch steps apart is two squares of shingles before waste. Confirm pitch with the free pitch finder, a street-level photo, or a gauge on site.
When oblique aerial wins
Angled photos earn their keep when the vertical matters: wall flashing runs, dormer cheek walls, parapet height, or a walkout basement that puts the back eave 20 feet up and changes your staging. They also show the overhang against the wall line, which helps when you price soffit and fascia.
They're less useful where the area hasn't been flown recently or the roof was replaced since the last flight, and they add a cost line to every job you pull.
When your own drone or phone photo wins
New addition not on the satellite picture yet? Fly it. Back slope buried under canopy? A drone above the trees sees it. Storm damage from last week? Only a fresh photo shows it.
Scale is everything. Every length is measured against your one known length, so an error there runs through the whole roof:
- You calibrate on a 16 ft garage door but click points 16.5 ft apart: lengths are off by 16.5 ÷ 16 = 3.1%
- Area scales with the square: 1.031 × 1.031 = 1.063, so area is off by about 6.3%
- On a 30-square roof, that's roughly 1.9 squares you didn't need, or didn't order
Pick the longest straight length you're sure of, at roof height if you can, and shoot as close to straight down as you can get. The more angled the photo, the more the far side of the roof shrinks against the near side. A phone photo from the ground is better for spotting damage than for tracing a whole roof.
Where RoofStruct fits
RoofStruct's self-serve measuring works on satellite imagery and on your own drone or phone photo. Satellite measurements set their own scale; an uploaded photo is calibrated with one known length, the same method as above. Both are free and unlimited, with the full PDF and no card. If you've never traced one, measure your first roof walks the steps.
When you'd rather not trace it, the done-for-you report is measured from high-resolution satellite imagery by a technician, checked by a second, and usually delivered within 4 hours (turnaround can vary with volume and complexity).
Where you trip
- Trusting the image date blindly. Look for a dumpster, a new deck or a different shingle color than the house has now. If the picture doesn't match, shoot a fresh photo.
- Tracing the wall instead of the roof edge. On an angled image the wall line and the drip line separate. Squares, drip edge and starter follow the roof edge.
- Calibrating on a short length. A one-click miss on a 3 ft vent is a far bigger percentage than on a 20 ft ridge.
- Assuming one pitch. A 12/12 front gable over a 4/12 porch needs two pitch factors, not an average.
- Skipping the lower roofs. Porch roofs and bump-outs under an upper eave hide in top-down shots.
FAQ
Is satellite or drone imagery more accurate for roof measurement?
It depends on the picture, not the platform. A sharp, recent satellite image of a clear roof can beat a drone photo calibrated on a bad reference, and a careful drone shot beats a blurry, shadowed satellite picture.
Can I measure roof pitch from aerial imagery?
Not from a straight-down picture. Angled and street-level photos let you estimate it from the gable shape, and a gauge on site settles it. Enter pitch per facet when the roof mixes slopes.
Do I need a license to fly a drone for roof measurements?
Commercial drone flights come with licensing and airspace rules in most places, and they differ by country. Check the current rules where you work before you fly a paying job.
What known length should I use to calibrate a drone photo?
The longest straight run you're sure of that sits flat in the frame: a measured ridge, a garage door you've taped, a gutter run. Avoid short items and anything at a different height than the roof plane you're measuring.
Pick the source that matches the roof, check the date, and check your scale.