Quick answer: A site survey is a measured record of what physically exists on a piece of land — surfaces, levels, structures, features, boundaries or volumes, depending on which type you are asking for. It is an umbrella term covering at least seven distinct jobs, and the one you need is set by what you will do with the result: design a building, price earthworks, define a boundary, or record a condition before works start.
An aerial survey is one method of capturing that information, not a separate category of survey. It suits some of those jobs very well, some only partly, and one not at all.
Where boundaries or disputes are involved, this is general information, not legal advice — talk to a licensed surveyor or your solicitor.
What is a site survey?
A survey answers “what is actually there, and where?” — measured, dated, and recorded in a form someone else can work from. That distinguishes it from an inspection, which forms an opinion about condition. The professional judgement happens downstream, when a designer, engineer, consultant or solicitor uses the record.
Which survey you need is set by the decision it feeds — design, planning approval, earthworks pricing, a dispute, a permit condition, a handover pack — and the accuracy that decision can tolerate.
Types of site survey
Here is what each one is for, and how well aerial capture fits.
Cadastral (boundary) survey
What it is: The legal definition of where a property boundary sits, tied to the Torrens title system and the survey marks in the ground. It produces a plan that can be lodged and relied on in fencing disputes, subdivisions and easements.
Who does it: A licensed surveyor, and only a licensed surveyor. In Victoria that means registration with the Surveyors Registration Board of Victoria; other states have their own. It is a regulated activity.
Aerial fit: not appropriate. No amount of drone imagery defines a legal boundary. Aerial data can show where a fence, wall or structure physically sits — often the thing actually in dispute — but the boundary comes off the title and the surveyor’s marks.
Topographic (contour) survey
What it is: The shape of the ground. Levels, contours, slopes, batters, drainage falls — the terrain model an architect or civil engineer designs onto.
Aerial fit: good, on open ground. Photogrammetric capture produces dense elevation data across a whole site quickly, and contours are derived from it. On heavily vegetated sites, ground survey or LiDAR does better.
Feature and level survey
What it is: The standard pre-design survey for a building project, combining levels with located features — kerbs, crossovers, pits, poles, trees, fences, service lids.
Aerial fit: partial. Orthomosaic imagery covers the visible surface and site-wide context well and makes feature identification straightforward. But design-grade work needs a qualified surveyor for invert levels, service locations and anything under cover. Aerial supplements it rather than replaces it.
Detail survey
What it is: A closer record of a defined area — a car park, an intersection, a building footprint, a length of road corridor — where the brief is precision over a small extent, not coverage over a large one.
Aerial fit: partial. Low flying gives very fine imagery detail and is efficient for surface features. Where the requirement is dimensional and tight, ground survey is safer.
Condition or dilapidation record
What it is: A dated record of the condition of structures and surfaces, taken before nearby works start, so any later damage claim has something to be compared against.
Aerial fit: strong. Roofs, upper facades, parapets, gutters and rear elevations are hard and often unsafe to photograph from the ground, and exactly where damage gets claimed later. The report itself is prepared by a building consultant or registered building inspector — we supply the imagery underneath it, not the assessment.
Volumetric (earthworks) survey
What it is: Measuring quantities. Stockpile volumes, cut and fill, extraction rates, landfill airspace, progress claims on earthworks.
Aerial fit: strong. Comparing two elevation models flown at different dates gives volume change across the whole site, not just along the lines someone walked. It is quick, repeatable, and keeps people off unstable ground.
As-built survey
What it is: The record of what was actually constructed, as distinct from what was drawn. Used for handover documentation, asset registers and variation discussions.
Aerial fit: good for external and above-ground work — pavements, hardstand, roofing, site layout. Not a fit for internal fit-out or anything buried.
What an aerial survey actually delivers
An aerial survey is not “some photos from a drone”. The photographs are the raw input; the deliverables are processed datasets.
Orthomosaic. Hundreds of overlapping images stitched and geometrically corrected into one continuous, scaled, top-down image. Unlike an ordinary photo, you can measure distances and areas off it. It is the base layer people drop into design software, planning submissions and reports.
DEM / DTM (elevation model). A grid of ground heights across the site. A DSM includes everything on the surface — trees, buildings, plant — while a DTM strips those out to model bare earth.
Contours. Derived from the elevation model at whatever interval suits the job — usually the first thing a designer opens.
3D point cloud. Millions of measured points describing the site in three dimensions, used for volumes, sections and visualisation.
High-resolution stills. Oblique and vertical frames for close inspection of a single feature — a roof junction, a retaining wall, a damaged kerb — delivered with metadata intact so the capture date and position travel with the file.
Downstream, those feed design and planning, earthworks estimation and progress claims, compliance reporting, and dated site records for permits, disputes and handover.
Ground sample distance, in plain English
Ground sample distance (GSD) is the practical measure of detail in aerial data: how much ground each pixel covers.
A GSD of two centimetres means one pixel represents a two-centimetre square on the ground. Smaller GSD, finer detail — you can resolve a hairline crack or a single roof tile. Larger GSD, coarser detail, faster coverage.
GSD is driven mainly by flying height and camera. Flying lower gives more detail but covers less ground per pass, so it takes longer and produces more data to process — the biggest single lever on quality and cost. Asking for the finest detail across a whole site, when you only need it on one structure, is the most common way to overspend.
What drives site survey cost
We do not publish a fixed price, because the same hectare can be a two-hour job or a two-day job. What moves the number: site size and shape; the GSD and accuracy required; whether surveyed ground control points are needed; airspace conditions, since controlled airspace or proximity to people may require approvals under CASA rules; which deliverables you want; and travel, as we are based in south-east Melbourne and take interstate work by arrangement.
When an aerial survey is the wrong tool
Dense tree canopy. If the ground is not visible from above, photogrammetry cannot model it — the elevation model describes the treetops, not the terrain. Ground survey or LiDAR is the answer there.
Anything sub-surface. Buried services, footings, drainage inverts, contamination, soil conditions. Aerial capture sees surfaces; service location and geotechnical work are separate.
Legal boundary definition. Worth repeating: only a licensed surveyor can define a boundary. We can show where a structure sits, not whose land it is on.
Indoor spaces. Interiors, roof cavities, subfloors and confined spaces are not aerial work.
Airspace-restricted sites. Some locations sit inside controlled airspace or close to aerodromes and helipads. Flying there may need approvals, may be height-limited, or may not be practical. We check this before quoting, not after.
Where a signed opinion is the deliverable. If you need a certified plan or a building report, engage the licensed professional. Aerial data is the layer underneath their document, not a substitute for it.
Frequently asked questions
What is the difference between a site survey and an aerial survey?
A site survey is the job: a measured record of what exists on a site. An aerial survey is one method of capturing it, using imagery collected from the air and processed into orthomosaics, elevation models, contours and point clouds. It suits topographic, volumetric, condition and as-built work well, but cannot define a legal boundary or see below the surface.
Can a drone survey replace a licensed surveyor?
No. Cadastral work — anything that defines a legal property boundary or produces a plan for lodgement — must be done by a licensed surveyor. Aerial data records the physical position of fences, walls and structures, which is useful supporting evidence, but the boundary comes from the title and the surveyor’s marks.
How accurate is an aerial survey?
Accuracy depends on flying height, camera, ground control and processing, so a single figure would be misleading. Two levers matter: ground sample distance, which sets the detail you can resolve, and whether surveyed ground control points are used, which sets how well the data ties to real-world coordinates. Tell us the tolerance you need.
How much does a site survey cost?
There is no standard rate, because scope drives everything: site size, required detail, whether ground control is needed, which deliverables you want, airspace conditions and travel. A single orthomosaic of a suburban block and a repeat volumetric survey of a quarry are different jobs. Send the address and what the data is for, and we will quote it.
What are the main types of site survey?
The common ones are cadastral or boundary, topographic or contour, feature and level, detail, condition or dilapidation, volumetric or earthworks, and as-built. Cadastral survey is the one restricted to licensed surveyors; the others can be served, fully or partly, by a range of capture methods including aerial.
Do you need a licence to fly a survey drone in Australia?
Yes. Commercial aerial work is regulated by CASA and requires a remote pilot licence and operation under an operator’s certificate, within the applicable operating conditions. Controlled airspace, aerodromes and proximity to people need additional approvals. We confirm airspace conditions for each site before flying.