You are drafting the appraisal for a conservation area review. The character text says the open land on the south side has been eroded over time, and the committee will want to know by how much. The tithe map gives you boundaries and the early Ordnance Survey editions give you buildings. Neither shows you what the ground looked like from above before the later development.
File · Conservation area review
See what this landscape looked like eighty years ago, on your own base map.
Scanned wartime and mid-century aerial sorties, orthorectified and set against a recent high-resolution pass, for the conservation area you are reviewing.
- Platform
- High-res satellite
- Resolution
- 0.5–2 m
- Spectral
- Panchromatic
- Cadence
- Decadal
- Thermal
- No
The baseline the appraisal is missing
The aerial photography exists. Sorties flown in the 1940s and 1950s sit in national and county archives, as prints and film that someone has to find, order or go and view, then scan. When the scans come back they are unregistered: tilted, stretched at the edges, with no relationship to your base mapping. Laying one over the modern map is hand work, picking control points in a GIS, repeated for every frame the site is split across. Many reviews cannot spare the time.
So the comparison gets done by eye across two windows, or it gets dropped from the appraisal, and the statement about change rests on the documentary record alone.
The pilot changes one step. The sorties are located, orthorectified and laid over a recent high-resolution pass for your site boundary, so the before and after sit in one project file.
What the pilot returns
The pilot covers one site or conservation area and one set of archival sorties. You agree the boundary and the period first. After that there is a single delivery, not a feed. Each item below lands in your GIS project or your site record.
2.1Orthorectified archival layer
Format GeoTIFF
The scanned frames for your site, corrected and registered to the recent pass so they overlay your base mapping. Each frame keeps its sortie date and its archive reference, and the frames that were used are listed, so the record shows exactly which day each view is from.
2.2Change-detection overlay
Format GeoPackage
Then against now, cut to your site boundary. Areas where the two dates differ are outlined as a change envelope, for field pattern, buildings, tracks and open land. Use it to see where boundary loss and new built form cluster.
2.3Reference frame set
Format PDF and image files
The archival frames prepared for reading, with the original scans kept alongside. Put them in the site record next to the appraisal, so the reviewer can see what the overlay was drawn from.
How it works
3.1Define the site
You send the site or conservation area boundary as a shapefile or GeoPackage, and the period you care about. Tell us what the work feeds: an appraisal, a desk-based assessment or a planning application.
3.2Locate the sorties
The archive coverage for your site is checked before any processing and you are told which sorties exist and from what dates. Coverage varies from site to site, so this step comes first.
3.3Orthorectify and compare
The scanned frames are corrected and registered, then compared with a recent high-resolution pass over the same boundary.
3.4Deliver for the record
The layers, the list of frames used and a short note on the quality of each frame go to you in formats that open in QGIS or ArcGIS.
Limits
These are stated here so the layers are not read as more than they are.
- L1Coverage depends on the archive
- Whether a usable sortie exists for your site, and from which years, depends on what was flown and what survives. Some sites have good coverage, others have little. The coverage check tells you before you commit.
- L2Registration is a working match
- How well a scanned frame lines up depends on the film, the scan and what stable ground control the site offers. Expect the match to be good enough to read change in fields, buildings and tracks, and not good enough to measure a boundary to the centimetre, so do not use it as a survey.
- L3Dates are the sortie's dates
- The layer shows the landscape on the day of the sortie and on the day of the recent pass. Nothing is dated more finely than the archive record allows, and nothing is inferred between the two.
- L4Black-and-white frames
- The old frames are panchromatic. You read them by tone, texture and shape, and there is no colour to separate crop from grass or roof from track.
- L5The recent pass sets the floor
- The recent pass is 0.5–2 m GSD. Fields, buildings and tracks are visible. A single-stone wall or a thin hedge is at the edge of what 0.5 m shows, and out of reach at 2 m.
- L6Decadal is a span
- Decadal describes how the comparison is framed, at roughly ten-year steps across the record. It does not mean a new comparison arrives every ten years on its own.
Who it's for
- Heritage planning officers and conservation officers reviewing a conservation area or writing an appraisal.
- Consultants and county archaeology staff preparing a desk-based assessment that needs a historic baseline.
- Teams with a defined site boundary and a question about how the landscape has changed since the mid-century.
Who it's not for
- Teams that want a boundary or a building footprint measured to the centimetre.
- Research that needs every frame an archive holds for a site. This works with the sorties that turn up for your boundary.
- A replacement for documentary and field research. It sits beside the tithe map and the site visit.
- Live monitoring of a site. The comparison is a one-off layer at a set of dates.
Questions from planning and heritage teams
Which sorties will you find for our site?
It depends on archive coverage, and no site is guaranteed one. The coverage check comes before processing, and you see the list of what exists before anything else is agreed.
How precise is the orthorectification?
It depends on the quality of the scan and on the ground control the site offers. It is good enough to compare field pattern and buildings across the two dates. It is a working match, not a survey registration.
Does decadal mean an update every ten years?
No. It describes the span of the record and the steps it is read in. The pilot is one delivery, and further deliveries are a separate conversation.
Can this replace documentary research?
No. The tithe map, the early maps and the written record still carry things that no aerial frame shows. This is a visual layer to set next to them.
What does panchromatic mean for reading the old frames?
They are black and white, so you read tone, texture and shape. Field boundaries, buildings and tracks read well. Crop type and surface colour do not.
Can we check the overlay against our own records?
Yes. Every frame carries its sortie date, so the change envelope can be set against your Historic Environment Record, earlier survey notes or photographs from a site visit of a known date.
Who owns the delivered layers, and what about the archive's own terms?
Ownership and use of the delivered layers are set out in the contract before work starts. The source archives have their own licence terms for the frames, and those are passed on with the delivery.
How is a pilot priced?
Each pilot is scoped on its own: site size, how many sorties exist, and the period covered. You get a written scope to take through your authority's procurement.
Send us the boundary and we'll tell you what archival coverage exists for it.
Or ask about your conservation area .
Start a pilot