Common questions
How do you calculate ground sample distance for a drone survey?
GSD in centimetres per pixel is the physical sensor width in millimetres, times altitude in metres, times 100, divided by the true focal length in millimetres times the image width in pixels. The 100 converts metres to centimetres, and the two millimetre figures cancel, which is why the formula needs a physical sensor width rather than a crop factor. The mistake that quietly ruins a spreadsheet is using the 35 mm equivalent focal length alongside the real sensor width: the answer still looks plausible and the flight comes back at the wrong resolution.
Why does raising overlap from 70% to 80% cost so much more than it sounds?
Because image count scales as one divided by the product of the two remaining fractions. At 70% front and 70% side you keep 30% of each, so the count goes as 1 / (0.3 x 0.3). At 80/80 you keep 20% of each, so it goes as 1 / (0.2 x 0.2). That is 2.25 times the photographs for what sounds like ten more percent. Airtime rises much less, around 1.5 times, because only side overlap adds flight lines — front overlap just triggers the shutter more often along a line you were already flying. So the airtime barely moves, the image count more than doubles, and the processing bill follows the image count. A pilot quoting by the acre absorbs that difference personally.
Does a finer GSD mean a longer flight?
Yes, and roughly as the square. A finer GSD needs a lower altitude, a lower altitude gives a smaller ground footprint per frame, and a smaller footprint means both more flight lines across the site and more exposures along each one. Halving the GSD halves the altitude, which halves the footprint in both directions and so roughly quadruples the image count and doubles the number of lines. Agreeing a resolution on a call without pricing it again is one of the more expensive habits in this trade.
Can I fly high enough to get any GSD I want?
No. 14 CFR 107.51(b) caps a small unmanned aircraft at 400 feet above ground level, which is 121.92 metres, unless you are within 400 feet of a structure or hold a waiver. If a coarse target GSD would need more altitude than that, you fly at the ceiling instead, get a finer GSD than the client asked for, and cover less ground per pass — so the flight takes longer than an unrestricted plan suggests. This calculator flags that case rather than quietly planning an illegal altitude. It does not grant any authorisation, check airspace, or file anything: LAANC, airspace class and currency remain entirely yours.
What does this assume about the shape of the site?
That it is square. Acreage alone does not determine a flight — a long thin corridor and a square block of the same area fly very differently — and a square is the shape with the least perimeter for a given area. That makes this the optimistic end of the range rather than a neutral guess, so real flights over awkward parcels run longer, not shorter. Treat the airtime as a floor. For a corridor job, price it from the corridor length and swath width instead of from acreage.
Is margin the same as markup?
No, and confusing them is how a job that looked profitable is not. Margin is a share of the price: a 40% margin means price equals cost divided by 0.6. Markup is a share of the cost: adding 40% to cost gives price equals cost times 1.4, which is only a 28.6% margin. On a $1,000 job the margin figure quotes $1,667 and the markup figure quotes $1,400 — a $267 difference on one sortie, repeated on every job. This calculator takes margin on the price, which is what pilots mean when they say it.
Is any of this uploaded?
No. There is no account and the page makes no network requests — it runs entirely in your browser. Your site areas, your hourly rates, the margin you quote at and the jobs you price are never sent anywhere and never appear in a usage count. The optional counter records only which features were used and the day, stored on your own device, and it switches itself off for browsers sending Do Not Track or Global Privacy Control.
Is this a flight plan, and can I fly from it?
No to both. It is a worksheet: arithmetic on figures you type. It is not a flight plan, not an airspace authorisation, and not aviation, legal or safety advice. It does not know your terrain, your obstacles, your airspace, the weather, your battery health or your aircraft's real endurance, and every one of those changes the flight it describes. Plan the actual mission in your ground control software, check airspace and obtain any authorisation you need, and treat these numbers as an estimate to quote from rather than a mission to fly.