Drone flights: from photos to products

Upload a flight, choose how it should be processed, and know what it costs before it starts.

8 min read

The workflow, in order

Create the mission and set its coordinate system, the grid every product should come back on.
Upload the flight's images. Backsight reads each camera position as it goes.
The camera positions are converted onto that grid, before alignment.
Add and mark ground control, if the job needs surveyed accuracy. Skip it if it does not.
Request the reconstruction: cloud, orthophoto and surface, all on your grid.

It is the order a photogrammetrist works in, and the order matters: converting first means the alignment itself happens on your coordinate system rather than being moved onto it at the end.

Set up a mission

Drone mode → Missions → New flight: a name, the day, and the coordinate system and vertical reference the products should be labelled with. Aircraft and sensor wait behind Details.
The mission opens on its four steps: Photos, Placing it on the ground, Process, Products. Each says whether it is done, and the next opens as you go.
Step 2 is a choice, not a requirement: the photos' own GPS (one click, no ground control needed), or surveyed control marked in the frames. Either is recorded on the mission and stated on every product.

Upload the flight

Choose the flight's images and upload them. Nothing is charged for this.
As each frame goes up, Backsight reads the camera position out of its EXIF, the GNSS fix the drone recorded, on WGS 84.
The panel then states how many frames carry a position, and what will happen to them.

Uploading is its own step

Marking ground control can only happen once the images are here, so uploading is separate from requesting the job. You are charged when a reconstruction actually starts.

The coordinate system, before anything is aligned

This is the step a photogrammetrist does first, and Backsight does it the same way: the cameras' WGS 84 fixes are converted onto the mission's own coordinate system before the photos are aligned. The whole reconstruction then happens on the grid the job is drawn on, and every product, cloud, orthophoto, surface, comes back on it. The alternative, letting the processor pick its own zone and moving the products afterwards, puts a transformation between you and your data for no reason.

What the panel tells you before you spend anything:

How many frames carry a camera position.
The coordinate system they will be converted onto.
The transformation used, its accuracy, and a reproducibility id.
Any frame that could not be converted, and any that carried no altitude.

A UTM zone needs no grid

Going from WGS 84 to a UTM zone on WGS 84 is a projection, not a datum change, so it always works. That is the quick answer for a small locate flight.

A NAD83 grid is a datum change

Converting a camera's WGS 84 fix onto NAD83 or NAD83(CSRS) needs a transformation grid. If your organization has not installed it, Backsight says which one and stops rather than using an approximate path by itself. Install it, set the mission to a UTM zone on WGS 84, reconstruct without it and bring the products onto your grid afterwards with ground control, or accept the approximate conversion deliberately (below).

When that happens, the panel offers one more choice: accept an approximate conversion for the camera positions only. It is worth understanding exactly what you are agreeing to, because Backsight refuses approximate work everywhere else and this is the single place it does not.

What the approximate conversion is, and is not:

Without the grid, the datum shift is computed from parameters alone, expect metres of agreement, not centimetres.
It applies to the camera seed positions only. Those are the starting guess the reconstruction refines against the imagery itself, which is why metres there usually cost nothing.
Surveyed ground control is never approximated. Where accuracy is the point, control carries it, on the accurate path, with no option to bend it.
The decision is recorded against the mission with your name and the time, and it is audited.
The operation is labelled APPROXIMATE, the geolocation file says so in its own header, and the job on your processing page says so permanently.
You can withdraw it at any time before requesting the job.

When it is the right call

A locate flight with no targets, where you want the products on your working grid and metre-level seed positions make no difference to the result. When the deliverable has to hold survey accuracy, install the grid or bring the job onto your grid with ground control instead.

Request the reconstruction

Ask what it will cost. The price comes from the number of photos, and is shown before anything starts.
Choose how it should be processed (below).
Request it. You are charged when the job starts, and refunded in full if it does not deliver.

Ground control is optional

A flight with no targets still reconstructs, on the camera positions alone, choose "Continue without ground control" in step 2 and the mission is ready to process. Add ground control when the job needs surveyed accuracy; skip it when it does not. A flight whose photos carry no GPS at all still reconstructs too; the model simply has no absolute position, and the products say so.

The processing settings

Setting	What it changes
Feature matching	How hard it looks for tie points between overlapping photos. Higher helps on low-texture ground, snow, fresh gravel, open water.
Point cloud density	How dense the cloud comes out. This is the one that decides whether a 200-photo flight takes twenty minutes or two hours.
Classify the ground while it processes	Ask the processor to sort ground from everything else as it goes, on its settings rather than yours.
Build a terrain model	A bare-earth model from that classification. Only meaningful with classification on.

Which quality should I choose?

Medium point cloud density with high feature matching suits most topo work. Go to ultra when the ground is featureless and the flight is small; the machine is rented by the hour, so ultra on a large flight is a real cost.

What you get, and what it says about itself

A point cloud, an orthophoto and a surface model.
The settings you chose and the exact processing flags they became, recorded on the job, so any product can be traced back to what made it.
A note stating how it was georeferenced, from marked survey control, or from the images' own GPS.

Georeference from your own survey

Mark your surveyed targets in the frames they appear in and the reconstruction is placed on your control rather than on the drone's GPS. See Ground control: marking targets in the images.