Key takeaways
- The product is remaining airspace, not a volume. Airspace is the gap between the surface today and the permitted final contour, so the answer depends entirely on which final surface you compare against.
- A drone measures one of the two surfaces. The other one, the cell base or liner as built, cannot be flown once waste is on it, so it has to come from your own construction records.
- Consumption rate matters more than the single number. Two captures a known interval apart give airspace consumed per month, which is what turns a volume into a remaining life estimate.
- Density is your assumption, not the survey's. Converting cubic metres of airspace into tonnes of future capacity needs an in-place density figure that comes from your own records.
- Daily and interim cover is in the measurement. The surface includes whatever soil is on top of the waste, so a capture right after a heavy cover application is not measuring waste alone.
- Cover thickness is a two-surface problem. You need a capture before the cover goes on and one after, and it cannot be recovered later from a single flight.
- Slope and crest geometry come free with the surface. Side slope angles against the permitted design, bench geometry and surface drainage all read directly off the same dataset.
- The dated record is the part most operators undervalue. An annual capture at the same time of year, in a consistent datum, is a defensible series rather than five unrelated numbers.
A landfill is one of the few sites where the drone survey question is almost never "how much is there". It is "how much room is left". That sounds like the same question turned around, and it is not, because the answer depends on a surface that does not exist yet.
Airspace is a comparison, not a measurement
Remaining airspace is the volume between the surface of the site as it stands today and the final contour your approval allows you to fill to. The drone measures the first of those two surfaces well. The second one is a design, and it has to be supplied.
This is where most disagreements about a landfill volume come from. If one engineer compared against the approved final contour and another compared against a practical working contour that stops short of it, the two will not agree, and neither is wrong. Before a flight is useful, somebody has to say which final surface is the reference and provide it as a surface model rather than a drawing.
The same goes for the bottom. Airspace in a cell that is partly filled is bounded underneath by the liner or the cell base as it was constructed. No aerial capture can recover that, because it is under the waste. It comes from the as-built survey done when the cell was built, and if that record is thin, the uncertainty in the airspace number is driven by the base rather than by anything the drone did.
What one capture gives you
A single flight of a waste cell, processed to a surface, produces a short list of things that are genuinely useful:
- The current filled surface, as a measurable model rather than an impression.
- Airspace remaining against whichever final contour you supply.
- Side slope angles and crest elevations, which can be checked against the permitted design.
- Surface drainage and ponding, which is usually visible immediately and often surprising.
- An orthomosaic of the working face, the cover extent and the perimeter at a scale nobody sees from the ground.
That is a useful annual deliverable on its own. It is not a remaining life estimate.
Remaining life needs two captures and your own tonnage
Remaining life is airspace divided by the rate at which you are consuming it. The rate is the part a single flight cannot produce. Two captures a known interval apart give airspace consumed over that interval, which is a directly measured consumption rate rather than one inferred from tonnage.
Both numbers are worth having, because they are checks on each other. Your scale records tell you tonnes received. The captures tell you cubic metres consumed. Dividing one by the other gives an in-place density for your own site and your own operating practice, which is far more defensible than a figure borrowed from a textbook. That density is then what converts remaining airspace back into remaining tonnes.
If the two disagree badly, the gap is usually explained rather than mysterious: cover soil counted as airspace consumed but not as waste received, a cell boundary drawn differently between captures, or a base surface that was never certain.
Cover is in your surface whether you want it there or not
Photogrammetry and LiDAR both return the top of whatever is there on the day. On an active landfill that is daily cover, interim cover, a tarp system, or exposed waste at the working face, in some combination. The surface is correct. It is just not a surface of waste.
Two practical consequences. First, if you want captures to be comparable, fly them at a consistent point in the operating cycle rather than whenever the schedule allows. Second, if you need to know how much cover soil is sitting on a lift, that is a two-surface problem: one capture before placement and one after. There is no way to extract it from a single flight afterwards, and once the next lift goes on, the opportunity is gone for good.
The annual report is a different deliverable from the operating number
Most Alberta operators have some annual reporting obligation attached to their approval, and the specifics vary by site and by approval rather than being uniform. What the survey can do is produce the evidence in a form that stands up: a dated capture, a stated accuracy with the method used to establish it, the datum and coordinate system written down, the base and final surfaces named with their revisions, and the unedited originals retained.
What a survey cannot do is decide whether you are in compliance. That reading is yours and your consultant's. Our job is to make sure the number in the report is traceable to a specific flight, a specific method and a specific reference surface, so that a later reader can tell exactly what was measured.
What a drone capture will not tell you
Being blunt about this early avoids an awkward conversation later. An aerial capture of a landfill does not see below the surface, so it says nothing about settlement at depth, waste composition, leachate levels, gas generation or liner condition. It does not assess the integrity of a berm, only its geometry. It cannot distinguish waste from cover soil by looking at the top. It does not establish the legal boundary of the facility, which remains an Alberta Land Surveyor's work.
It also cannot tell you what the surface looked like last year if nobody flew it last year. That is the recurring regret on sites like these, and it is the cheapest problem on the list to fix.
How to scope the first one
Four questions settle most of the scope. Which final contour is the reference, and can you supply it as a surface. What is the base surface of each cell in play, and how good is that record. What is the cutoff date the number has to be as at, since a landfill surface changes daily. And is this a one off or the first of a series, because a series means fixing the datum, the cell boundaries and the time of year now rather than discovering the inconsistency at capture three.
If the honest answer to the first two is that nobody is sure, that is still a useful outcome. It means the first capture establishes a baseline you control, and the airspace number improves as the reference surfaces get sorted out, rather than being quietly wrong forever.