Textured 3D model
3D photogrammetric model
The baseline itself, tied to ground control points. Delivered once after the first survey, then again after each review flight. It serves the rows on recording and on saying what moved.
Measure the change at your next review, not guess at it from photographs.
Heritage Documentation flies a drone or aircraft survey over your monument and returns a photogrammetric 3D model. That model is the baseline every later condition review compares against.
Measured baseline
- GSD
- UAV, under 10 cm
- Spectral
- RGB
- Platform
- Drone or crewed aircraft
- Cadence
- Baseline, then each review
Where a photo folder runs out
At the review you have last time's photographs and a condition form. You walk the site, try to find where the last photographer stood, and compare two pictures taken in different light from slightly different spots.
The top of the wall seems to lean further than before, so you write that down. Nobody can put a measurement next to it, so the note stays an opinion and the question goes to the next review, and to the next officer, with the folder.
One review, step by step
| Step | Photo folder and notes | Measured baseline |
|---|---|---|
| Recording the state on the day | Photographs from the positions you can reach on the ground, and notes on the condition form. | A survey flight over the monument, processed into a 3D model, an orthomosaic and a point cloud, with a written record of the survey date and coverage. |
| Finding the same view again | Old photographs, a guess at where the photographer stood, and whatever the light allows. | The review flight is processed the same way and laid onto the baseline, so the comparison does not depend on where anyone stood. |
| Saying what moved | Two pictures side by side, judged by eye. “It looks like it has dropped.” | The two models are compared, and a difference between them is something you can measure and point to. |
| Still yoursDeciding whether a difference matters. The comparison shows where two surveys differ. Whether that is movement worth acting on is a conservation judgement. | ||
| Evidence for a grant or a consent | A folder of captioned photographs and the officer's account of how the monument has changed. | A baseline record with the survey date and coverage, and extracts from the model that show the state of the monument on a named day. |
| The upper parts you can't reach | Binoculars from the ground, or scaffolding and rope access when the budget allows. | The upper masonry, parapets and roofline are captured from the air in the same survey, within the limits of the resolution. |
| Still yoursClose inspection. Looking at a joint or a crack with your hands and eyes, and calling in a structural engineer, stays on your list. | ||
What arrives after each survey
Point cloud
Point cloud export
The same surface as measured points, for your surveyor to open in their own software.
Scaled image
Orthomosaic
A flat, scaled image of the monument, for GIS and for measuring across a face or a footprint.
Written record
Baseline record
A short document with the survey date, what was covered and how the survey was tied to the ground. It is the page you attach to a grant application or a condition survey form.
Comparison
Review comparison
At each review, the new model compared against the baseline, so the differences are laid out for you to judge.
How it works
Access and flight plan
You tell us which monument, where a drone can fly and who holds site access. We agree the flight plan and any ground control points with you before anything is flown.
The survey flight
A drone or crewed aircraft flies the monument in daylight and a settled weather window, ahead of your review.
Processing
The photographs become a photogrammetric model, a point cloud and an orthomosaic.
Baseline delivered
You receive the model files and the baseline record. At each later review we fly again, process the same way and send the comparison against the baseline. The interval is your review cycle.
Limits
- Daylight and line of sight
- The survey needs daylight and a clear view of the monument from the air. Indoor spaces, covered spaces and anywhere a drone cannot be flown are not covered by this method.
- What sub-10 cm resolution shows
- At a pixel of up to 10 cm, the form of the monument is recorded well: the lean of a wall, a missing section, the run of masonry courses. Hairline cracks, fine mortar loss and surface decay are smaller than a pixel and are not recorded. A close inspection still does that.
- Vegetation and shadow
- Ivy, trees and deep shadow hide stone from above. Areas hidden in the baseline are hidden in the comparison too, and the record says where.
- A comparison, not an alert
- The comparison lays two surveys over each other. Nothing flags a difference automatically as a problem.
- Not an engineer's report
- This is a measurable record. It does not assess whether a structure is safe, and it does not replace a structural engineer's inspection.
Who it's for
Use this if
- You are the conservation officer responsible for a monument's condition record.
- Your reviews currently rest on a photograph folder and a condition form.
- You want each review to have something measurable to compare with.
Stay with your photo folder if
- The monument is indoors, enclosed or under cover.
- Drones cannot be flown there.
- You need a structural assessment, which is an engineer's work.
Questions before you book a survey
Does this replace a structural engineer's inspection?
No. It is a measurable record of how the monument looked on a given day. Judging what that means for the structure is an engineer's job.
How do we check it against our own records?
Put our model beside the photographs and measurements you already hold for the same monument, and see whether the features you know line up. You decide whether it is good enough to work from.
Can this show movement between reviews?
The differences between two surveys can be compared. Whether a difference is significant is a conservation judgement and stays with you.
What if the monument is indoors or under cover?
The method needs daylight and a line of sight from the air. Tell us before you book and we will say whether it fits.
How often should we re-survey?
That follows your own review cycle. We do not set an interval.
What resolution does it reach?
From a drone, under 10 cm a pixel. That records form and masonry courses. It does not record hairline cracks.
What files do we receive, and can we open them ourselves?
A textured model, a point cloud, an orthomosaic and a written baseline record. The point cloud and the orthomosaic are for your surveyor's and your GIS software.
Who owns the survey data and the imagery?
Ownership and licence terms are written into the agreement before any flight. If your legal team needs to read them, ask for them early.
How is a survey priced?
It depends on the monument, the site access and how many reviews you want covered. We price it for your site.
Set the baseline before the next review.
Tell us which monument and when the review falls. We will tell you whether a survey can be flown in time.