Aerial Capture for a Development Permit, Subdivision or Rezoning

Planning applications in Alberta get held up on completeness more often than they get refused on merit. A development permit, a subdivision application or a rezoning goes in, and then a development officer asks for the thing that was missing: what is actually on the land now, where the existing access is, what the drainage does, how the proposal sits against the parcels on either side. Each of those questions is another round trip and another month.

Aerial capture answers a specific subset of those questions well and another subset not at all. The difference is worth being precise about, because an applicant who hears "we will fly it" and assumes that covers the survey requirement is going to have a bad meeting.

Who is reading the file, and what each reader wants

Three different readers touch a planning application, and they want different things from the same imagery.

• The development officer or planner is checking the application against the land use bylaw and the statutory plans. They want current existing conditions, setbacks and dimensions they can see, and confidence that the drawing matches the ground.
• The subdivision authority is looking at parcel geometry, access, servicing and whether the lots created are usable. They work from a surveyor's plan, with context imagery alongside it.
• Council, at a rezoning or a public hearing, is reading an unfamiliar site in a few minutes, usually alongside adjacent landowners who have opinions. They want to understand where this is and what is around it.

The first and third readers are where a capture earns its cost. The second reader is the one who needs a surveyor regardless.

What a capture is genuinely good for

On an Alberta planning file the recurring useful products are these:

• Existing conditions at a stated date. A georeferenced orthomosaic of the parcel and a margin around it, flown at a ground sample distance where fences, approaches, buildings, yards, laydown areas and bare ground are all unambiguous.
• Context. One image showing the subject parcel, the road network, the adjacent uses and the distance to whatever the application is really about, whether that is a residence, a school, a watercourse or an existing industrial neighbour.
• Vegetation and tree cover. Canopy extent is easy from the air and tedious on the ground. Where a bylaw or an area structure plan cares about tree retention, a capture shows what exists before anybody clears anything.
• Drainage and surface water behaviour. A photogrammetric surface with contours shows where water goes on the site today. On flat land this is approximate, and it is still more than most applications contain.
• Existing access and approaches. Where the driveway actually meets the road, how far it sits from an intersection, and whether what is built matches what was approved.
• Encroachments and surface conflicts, visible ones. A shed over a line, a neighbour's fence inside the parcel, a trail crossing the property. The capture flags it. A surveyor confirms it.

Most of that is readable off a single well made ortho and a contour set. It is not an exotic deliverable and it does not need an exotic sensor.

What still needs an Alberta Land Surveyor

This is the part that gets people in trouble, so it is worth stating without hedging. In Alberta, the legal description of land and the survey plans that get registered are the exclusive work of an Alberta Land Surveyor. That covers:

• The plan of survey that creates new titles when a subdivision is registered.
• Any statement about where a property boundary is, including whether something encroaches across it.
• A Real Property Report, where one is required for a permit or a transaction.
• Legal survey monuments, their recovery and anything that depends on them.

A photogrammetric product cannot do any of those, no matter how accurate it is, because the limitation is legal rather than technical. The sensible scope on a subdivision file is both: the surveyor produces the registrable plan, the drone capture produces the existing conditions record and the context imagery, and they get tied to the same coordinate system so the planner is not looking at two site plans that do not line up. We cover the broader version of that question in who signs off drone survey data.

What still needs an engineer

Servicing and stormwater are the other hard line. A municipality reviewing a subdivision or a larger development permit will want a stormwater management plan, a grading plan, and servicing design, sealed by a professional engineer. Aerial capture feeds that work and does not replace it. What the engineer gets from the flight is a current surface to design against, existing invert and structure locations where they are visible, and the catchment context around the parcel. What the engineer still has to do is the design, the modelling and the seal.

The same applies to anything geotechnical. A slope on the parcel is a surface in the capture and a subsurface question in the investigation, and only one of those is answered from the air.

The accuracy and datum questions a planning file creates

Planning files have a habit of collecting data from several sources over several years, and then somebody overlays them. That is when a coordinate system mismatch surfaces, usually as a proposal that sits a metre and a half off the parcel it belongs on.

Settle three things before the flight:

• The horizontal system, which should match whatever the municipality and the surveyor are working in rather than whatever is convenient to process in. Our note on which coordinate system your survey should be in goes through the Alberta options.
• The vertical datum and geoid model, which decides whether your elevations agree with the municipality's drainage data. A mismatch here looks like a smooth regional offset rather than an obvious error.
• Ground control, because a planning application that will be argued over deserves independent checkpoints rather than an assumed accuracy. How many is a separate question, covered in how many ground control points you actually need.

The public hearing, which is a communication problem

A rezoning or a redesignation goes to a public hearing, and the applicant who shows up with a plan sheet and a verbal description is at a disadvantage against a neighbour with a grievance and a phone full of photos. An annotated aerial changes that conversation. It shows scale honestly, it shows what is already there, and it answers the two questions that come up every time: how close is this to me, and what is between us.

The useful format here is not the technical deliverable. It is two or three annotated images at a size that reads on a screen in a council chamber, with the subject parcel outlined, the distances labelled and nothing exaggerated. Imagery that is obviously staged to flatter the proposal gets treated as advocacy, which is the opposite of the intent.

Timing and season, which matter more here than elsewhere

On an industrial measurement job the flight date is usually driven by the schedule. On a planning file it should be driven by what the application has to show.

• Snow cover removes ground detail, hides grade and makes a drainage argument unconvincing. A winter capture is fine for context and poor for existing conditions.
• Full leaf cover leaves little of the ground under trees visible from above. If the application cares about what is beneath a stand of trees, fly in spring or late fall, or accept that LiDAR is the real answer.
• Spring runoff is the window where a drainage problem is usually visible rather than inferred, which makes it a strong capture window on a wet site and a poor one for grade. A heavy summer rain event does the same job if somebody is ready to fly it.
• Application deadlines run on municipal calendars, and a flight needs weather. Build a week of slack in rather than a day. Our note on wind limits on a drone survey explains why the forecast, not the schedule, decides.

Scoping it so the deliverable is actually usable

Ask for the formats the people reading the file can open. A planning department may want a PDF figure and a georeferenced image for its GIS. A consulting engineer wants the surface and contours in CAD. A surveyor wants the control report and the coordinate system stated plainly. The failure mode is a point cloud nobody on the project team can load, which we have written about in who can open your deliverable files.

A reasonable package for an Alberta planning application looks like: an orthomosaic as a georeferenced image and as a scaled PDF figure, a contour set at an interval the municipality accepts, two or three annotated context images for the hearing, a short methodology and accuracy statement, and the raw imagery retained in case somebody challenges a measurement later.

Where this capture stops

Stated plainly, so nobody buys the wrong thing:

• It is not a boundary determination and not a registrable plan.
• It says nothing about anything below grade, which includes buried services, soil conditions and groundwater.
• It is a record of one date. If the application process runs eighteen months and the site changes, the capture needs refreshing.
• It does not evaluate compliance. A planner decides whether what the imagery shows meets the bylaw. The imagery just shows it.

Within those limits it is one of the cheapest things on a planning file, and it tends to pay for itself the first time it removes a request for information.