Key takeaways
- The shot sets the schedule. On a blasting site the survey window is whatever the blast plan leaves, and a flight is fitted into it rather than booked against it.
- The blaster in charge controls the area. Once holes are loaded, access to the pattern and the surrounding exclusion zone is their call, and a drone crew is a contractor under that control like anyone else.
- A drone is a radio transmitter. Where a site restricts radio transmission near loaded holes, that restriction applies to us, and the blast contractor is the one who says what the limit is.
- Nothing flies during the shot and nothing flies into the dust. The aircraft is grounded and off the pattern for the blast, and the post blast capture waits for the cloud to clear and for the all clear.
- Pre and post blast captures are a pair or they are nothing. A muck pile volume needs the surface before the shot and the surface after, in the same datum, against the same boundary.
- The pre blast flight has a deadline that is not the blast. It has to happen before the pattern is drilled and loaded, because once holes are loaded the crew cannot walk the bench to place ground control.
- Muck is the hardest material a drone measures well. Loose rock with deep voids means the surface is honest and the tonnage conversion is where the uncertainty lives.
- Face and highwall geometry is the quiet win. The same capture gives face angles, crest and toe positions, bench widths and burden at the face, which is drill and blast design input rather than just a volume.
On most sites the question is when we can fly. On a site that blasts, the question is what the blast plan leaves us, and the honest answer is that we work around the shot rather than the shot working around us.
This is not a difficult site type to work on. It is a site type where turning up without having talked to the blast contractor first wastes a mobilization.
Who actually controls the window
Once a pattern is drilled and loaded, the blaster in charge controls the pattern and the exclusion zone around it. A drone crew is a contractor working under that control in exactly the same way a haul truck or a surveyor on foot is. That means the useful first phone call is not to the site superintendent about access, it is to whoever is running the shot about timing.
Two things usually come out of that call. The first is the blast window itself, which is often a known time of day on a known day of the week, and which is the hour nothing else happens on site. The second is whatever your site's rules are about radio transmission near loaded holes. A drone and its controller are a radio link. Where that restriction exists, it applies to us, and the person who defines it is the blast contractor rather than us. We ask, we take the answer, and we plan the flight outside it.
The pre blast flight has an earlier deadline than people expect
If the point of the exercise is a blasted volume, you need two surfaces: the ground before the shot and the ground after. The second one is easy to schedule, because it is simply after the all clear. The first one is where sites get caught.
The pre blast capture has to happen before the pattern is loaded, not before the shot. Those are different dates, sometimes by several days. Once holes are loaded, nobody is walking the bench to set and survey ground control points, and often nobody is walking the bench at all. If the flight is left until the day before the shot, the only option left is a capture with on board positioning and no ground control, which may be fine for a progress record and is usually not what somebody wanted when they asked for a blasted tonnage.
The practical sequencing on a site that blasts on a regular cycle is to fly the bench as part of the drill and blast preparation rather than as a survey event. It lands in the right window by default.
What the post blast capture measures, and what it does not
After the all clear and after the dust has settled, a flight over the muck pile produces a surface. Compared against the pre blast surface, that gives a volume of material moved, swell against the in situ volume, and the shape and spread of the pile.
Muck is the hardest material a drone measures accurately, and the reason is not the drone. The surface model is correct: it is the top of the broken rock. What is underneath is loose rock with voids, and no aerial method sees into them. So the volume of the pile as a geometric solid is a good number, and converting it to tonnes of rock requires a swell factor and a density that come from your own site records rather than from the survey. Presented honestly, that is a useful figure with a stated assumption attached. Presented as a confident tonnage with no mention of the conversion, it is the kind of number that causes an argument three months later.
The other thing the post blast capture shows clearly, often more usefully than the volume, is how the shot actually performed: throw and displacement, whether the pile sits where the design wanted it, oversize visible on the surface, backbreak at the crest and any obvious misfire indicators. None of that is a substitute for the blaster's own inspection, and it should not be read as one, but as a dated record of what the shot did it is hard to beat.
Face and highwall geometry comes with it
The same dataset that gives you a volume gives you the geometry of the face, and on an active pit or quarry that is frequently worth more than the volume. Face angles and crest and toe positions, bench widths against the mine plan, and the actual burden at the face rather than the assumed burden all read off the surface directly.
That last one matters for the next shot. Drilling a pattern against an assumed burden when the real face has a bulge or a slump in it is how you get flyrock risk and poor fragmentation in the same shot. A pre drill capture of the face is cheap input into the blast design, and it is the use case most often missed by sites that already fly for monthly volumes.
Scheduling a site that blasts every week
Where blasting is routine, the pattern that works is to anchor the capture cycle to the blast cycle rather than to the calendar. Fly the bench before loading, fly the muck after the all clear, and let the monthly or quarterly inventory capture be a separate pass over stockpiles and the wider site that is not tied to a shot at all.
Keeping the inventory flight separate from the blast flights matters because they want different things. The inventory capture wants consistent conditions and the same boundary every time so the series is comparable. The blast pair wants to be as close to the shot as the loading schedule allows. Trying to make one flight do both tends to produce a volume that is neither a clean inventory number nor a clean blast number.
What we need from you before the first flight
A short list, and most of it is information rather than effort. The blast schedule, or at least the usual day and time. The name and contact for the blaster in charge. Whether your site restricts radio transmission near loaded holes, and what the restriction is. The exclusion zone boundary, so the launch point and the flight path sit outside it. Your site orientation and escort requirement. And the one decision that is yours rather than ours: whether you want a blasted volume, in which case the pre blast capture has to be scheduled before loading, or a post blast record, which is easier and answers a narrower question.