Key takeaways
- Breakup is a ground access problem, not a flying problem. The aircraft is fine. Getting a vehicle and a crew to the site is the constraint.
- Road bans are set by the road authority, not by us. A county, a municipality or the province restricts axle weights during thaw, and a light survey vehicle is usually permitted, but the lease road past the gate is a separate question with a separate owner.
- A thawing surface moves. Soft ground, frost heave coming back down and water sitting in low spots all change the elevations you are measuring, which matters more than any of it if the capture is part of a series.
- The worst window for a comparable measurement is the few weeks when snow is partly gone. Patchy cover is harder to correct for than full cover.
- Standing meltwater does not get measured through. Photogrammetry returns the top of the water, so a flooded pit floor or a low area reads as ground at the wrong height.
- Ground control placement is the quiet casualty. Walking a site to set and survey control points is slower and sometimes not possible on saturated ground.
- Plan the annual capture dates around breakup rather than through it. Late winter on firm frozen ground and early summer once the surface has dried are both better than April.
- If the work genuinely cannot wait, say so early. There are scope changes that make a breakup flight usable, and they are easier to arrange before the date than after the crew is on site.
Every spring we get the same two calls. One is a client who needs a volume before a quarter closes and wants to know whether we can fly next week. The other is a client who assumed we shut down for a month and is surprised we did not.
Neither assumption is right. Spring in Alberta does not stop drone work the way a storm front does. The aircraft does not care that the ground is thawing. What breakup actually does is make the site harder to reach, harder to stand on, and for a few weeks, harder to measure in a way you can compare against anything else. Those are three separate problems and they have different answers.
What breakup actually restricts
Breakup is the period when the frost comes out of the ground and the sub-base loses the strength it had all winter. Roads built on that sub-base lose capacity with it, so road authorities protect them by restricting axle weights for the duration. In Alberta that means the province on provincial highways and each county, municipal district or municipality on the roads it owns. The dates are not fixed in advance and they are not the same everywhere, because they follow the thaw rather than the calendar.
For a drone crew the practical reading is this. A half ton with survey gear in it is nowhere near the weights a road ban is written to stop, so the public road is rarely the problem. The problem is almost always past the gate:
- The lease road or site access road. Owned by the operator, the landowner or whoever holds the surface rights, and governed by their rules rather than the county's. Plenty of sites close their own access during thaw whether or not a ban is posted, and that decision is made by the site, not by us.
- The approach and the pad. A road that holds a vehicle does not guarantee a place to park, launch and set up that is not a soft shoulder.
- Walking the site. This is the one that gets underestimated. A capture that needs ground control needs a person walking the area of interest to place and survey points. Saturated clay, a thawing pit floor and standing water are the difference between a one hour setup and a bad afternoon.
- Escorts and site readiness. Sites in breakup are frequently running reduced operations, and the person who would have escorted a visitor is doing something else. That is the same access conversation covered in how to prepare your site for a drone survey, with a narrower window to arrange it in.
Where a site touches a provincial highway, a municipal road allowance or a rail corridor, the ground occupation permission is already a separate ask from the airspace, and breakup adds a reason for the road authority to say not yet. That split is covered in working beside a highway, road allowance or rail corridor.
Measuring a surface that is moving
Access is a scheduling problem. The measurement problem is more interesting, and it is the one that costs people money without them noticing.
A drone survey records the surface as it was on the day. During breakup the surface is genuinely changing week to week, and in several ways at once:
- Frost heave settling back. Ground that rose over winter comes back down, not uniformly.
- Partial snow cover. Full snow cover is a known problem with a known treatment, described in surveying stockpiles and sites under snow. Patchy cover is worse, because the surface is part ground and part snow of unknown depth and the dataset gives you no way to tell which is which at a given point.
- Standing meltwater. Photogrammetry returns the top of whatever light reflects off, so a water surface reads as ground at the water's height. A flooded pit floor or a low area holding melt will measure as fill that is not there. LiDAR does not rescue this either, since water absorbs most of the pulse.
- Soft material moving. A stockpile of saturated fine material does not hold the same geometry it held in February, and the toe is where that shows up first.
If the capture is a one off and the question is coarse, such as what does the yard look like or how far has the site progressed, none of that matters much. If the capture is one point in a series, all of it matters, because a breakup flight inserted into a monitoring programme produces a step in the numbers that is seasonal condition rather than material movement. The base surface and datum discipline that keeps a series comparable is covered in setting a re-fly cadence and in the base surface glossary entry, and breakup is the season most likely to break it.
Where to put the dates instead
The useful move is to plan the year so that nothing important lands in the thaw. For most of the sites we work on in Alberta that produces something like this:
- Late winter, on firm frozen ground. Access is at its best and the surface is stable, which is why a lot of annual aggregate and construction captures sit here. The trade is short daylight and low sun angle, both covered in the winter daylight window, and the cold weather operating envelope described in winter drone operations in Alberta.
- Through breakup. Treat as unavailable for anything you intend to compare. Keep it for coarse visual capture, incident response and work that genuinely cannot move.
- Early summer, once the surface has dried. The best all round window. Long days, firm ground, the surface at something close to its normal state and vegetation not yet at its worst.
- Mid to late summer. Good, with two caveats. Vegetation is at maximum, and smoke season can take days or weeks out of the calendar, as set out in flying in wildfire smoke.
- Fall, before freeze up. The other strong window, and the usual choice for a year end inventory capture because it lands close to the cutoff with the ground still readable.
For a town or county building a repeating programme, this is a budgeting question as much as a technical one, and it fits the annual cycle described in building a repeating municipal capture programme. The same logic applies to a private operator with a quarterly inventory: pick the dates once, keep them, and let breakup fall in the gap on purpose.
If the flight genuinely cannot wait
Sometimes the date is not negotiable. A quarter closes, a claim is open, a contractor is demobilising, or a number is needed for a report with a statutory deadline. In that case the flight is usually still possible, and the scope is what changes:
- Narrow the area of interest. Fly the piles and the pad rather than the whole property. Less walking on soft ground, fewer control points, less exposure to the parts of the site that are impassable.
- Decide about ground control deliberately. Where absolute accuracy is not the point, an on board positioning workflow avoids the walk entirely. Where it is the point, expect the control placement to drive the day, and expect to discuss what can be reached. The trade offs are in how many ground control points you actually need.
- Flag the water. Ask for standing water to be delineated in the deliverable rather than silently included as terrain, so anybody reading the volume later knows which areas are not real ground.
- Accept a condition note. A short record of what the surface was doing on the day is what lets a future reader discount the number correctly instead of treating it as comparable. That is the same methodology record that makes a capture defensible in aerial imagery as evidence.
- Keep the date flexible by a few days. Thaw conditions change fast. A window beats a fixed date, and it is also cheaper to serve, which is part of why scheduling flexibility shows up in what drives the price of a drone survey.
Weather still applies on top of all of this. Breakup brings wind, and wind has its own hard limits, covered in wind limits on a drone survey.
What to say when you call in March
Five things make the conversation short:
- Where the site is, by legal land description or a pin.
- Who controls the access road past the public road, and whether they have closed it.
- What is being measured, and whether the number will be compared against an earlier capture.
- Whether the date is fixed, and what it is fixed by.
- Whether anybody walks the site today, which is the fastest read on whether a crew can.
If you are not sure which window suits the work, tell us what the number is for and we will tell you whether a breakup flight will answer it or quietly mislead you.