Structure polygons and candidate plot lines for unsurveyed ground.
One VHR pass over your settlement or district boundary, delivered as two layers that load into your cadastral GIS.
Spec table
- GSD
- ≤0.5 m (VHR)
- Cadence
- Annual
- Platform
- VHR satellite / aerial
- Spectral
- RGB
- Formats
- Shapefile, GeoJSON
- Delivery unit
- one settlement or district boundary you supply
- Coordinate system
- the one your GIS uses
The files
- PM-01
Structure polygons
- Format
ShapefileGeoJSON- What's in it
- One polygon for every built structure the pass shows, each carrying a unique structure ID. Areas are in square metres. The ID is the key you print on the community sheet and carry into the adjudication record, so a correction made at a meeting points at one polygon and no other.
- Delivered
- Each pass
- PM-02
Candidate plot lines
- Format
ShapefileGeoJSON- What's in it
- Line layer. Proposed plot boundaries inferred from where the structures sit and where people walk between them. Each line is a proposal for claimants to confirm or move at adjudication. None of them is a legal boundary, and the layer says so in its metadata.
- Delivered
- Each pass
- PM-03
GIS-ready export
- Format
ShapefileGeoJSON- What's in it
- Both layers delivered together in the coordinate system you name, so they open in QGIS, ArcGIS or your national land information system beside the parcel fabric you already hold.
- Delivered
- Each pass
- PM-04
Review flags
- Format
Attribute field- What's in it
- A flag on every polygon sitting in a cluster too tight to trust, so your technician knows which roofs to check against the imagery before the sheets are printed.
- Delivered
- Each pass
- PM-05
Repeat pass
- Format
Annual- What's in it
- The same boundary delineated again a year on, so structures built since the first layer can be compared against it.
- Delivered
- A year on
How it works
You supply
Area in
The settlement or district boundary as a shapefile or GeoJSON, and the coordinate system your GIS uses. If you already hold a boundary file or a partial parcel layer for the area, send that too.
We source
Imagery
A very high resolution RGB pass over the boundary, from satellite or aerial. You do not need to supply imagery.
We run
Delineation
Structures are segmented first. Candidate plot lines are then generated from the structure layout and the access paths between them.
You receive
Delivery
Structure polygons, candidate plot lines and review flags, exported in the formats above.
Limits
- Dense and overlapping roofs
- At 0.5 m a pixel is half a metre across. A small hut is only a handful of pixels wide, and two roofs with a gap of a pixel or two between them can merge into one polygon. The delivery flags those clusters for a manual look. Expect to check them.
- Plot lines are proposals
- Candidate plot lines come from structures and access paths. A fence, a hedge, a boundary tree or an agreement between neighbours does not show from above. Claimants have the last word.
- Optical, daylight only
- The imagery is RGB. Cloud, haze and deep shadow hide ground, and nothing under tree canopy gets delineated.
- Structures, not rights
- The layer shows what is built. It says nothing about who holds which plot, and it is not a survey record or a title.
- Annual is the target
- The plan is one pass a year, weather permitting. It is not a monitoring feed.
Why this exists
Regularization in an area with no survey record starts from a blank map. A technician traces roofs by hand from whatever imagery the agency holds, before a single claimant has been asked anything. The tracing sets the pace of the programme, and the sheets for the community meeting are late because of it. Starting from a drawn layer means the meeting can be about where boundaries run.
Who it's for
- Land agency GIS officers preparing the base layer for tenure regularization or first registration.
- Cadastral systems leads who need structure and candidate plot layers in a format their parcel fabric accepts.
- Development programme staff running participatory mapping in a settlement with no survey record.
Who it's not for
- Programmes that need a legal boundary, a survey-grade plot or a title. That takes a licensed surveyor and formal adjudication.
- Teams that need rights, ownership or occupancy data. The layer shows structures only.
- Projects that need weekly or near-real-time change detection. The pass is annual.
Questions from the GIS desk
Does this create legal title?
No. It is a delineation layer for adjudication. Title comes from the agency's own process.
How accurate are the plot lines?
They are candidate boundaries inferred from structures and access, and we give no accuracy figure for them. Field adjudication is still required.
What happens where structures are dense or overlapping?
Very tight clusters can merge into one polygon. Those polygons carry a review flag so you can check them against the imagery.
What resolution do you need?
VHR, 0.5 m or finer. Small informal structures are hard to separate at coarser resolution, which is why the pass is 0.5 m or finer.
Can it cover a whole district at once?
It is scoped to the boundary you send. Tell us the size of the area and we will say how we would split the pass.
Which coordinate systems and formats?
Shapefile or GeoJSON, in the coordinate system your GIS uses.
How do we check it against our own survey?
Overlay it on any ground points, GPS tracks or existing survey you hold and tell us where it is wrong. We will go through the imagery with you.
Who owns the layers, and what about the imagery?
Use and ownership terms for the layers are written into the agreement before work starts. The imagery provider's licence applies to the imagery itself.
How is it priced?
It depends on the size of the area and whether you want the repeat pass, so we quote after seeing your boundary. There is no price list on this page.
Send the boundary, get a layer to adjudicate from.
Send the settlement or district boundary and the coordinate system your GIS uses. We will scope the pass from there.