How OMNID finds a building’s built-up area

Drone imagery first, the existing register alongside it, on-site capture for what neither can see. Eight short chapters; the same words the dossier uses.

Open the mapCapture on a phone
Chapter 1

OMNID is a temporal digital twin. Property tax is its first job.

Every flight, register extract and site visit becomes a dated epoch in a vault. Buildings keep one identity across epochs, so the question is never only “what is here” but “what changed, since when, and how sure are we”.

The platform is decision support. It writes findings, never a register. An officer reviews every flag; corrections are stored as audit records.

Already on the mapCount
GCC register buildings, every ward of Chennai924,340
Electricity connections with no register building under them98,288
GST registrations joined onto buildings27,870
Encrypted contact records in the PII vault504,369
Cadastral parcels, statewide5,072,033
Chapter 2

Three ways to a building's built-up area

Built-up area is footprint × floors. Each factor can come from a different source, and the dossier shows which one it used and how sure it is.

SourceGivesProvenanceWhen it wins
Drone surveyroof footprint, height, floors from DSM − DTM, ± sigmaOBSERVEDalways, once a flight covers the ward
Existing registerfootprint polygon, usage, bills, connections, GSTINOFFICIALfootprint until a flight; floors only when the assessment CSV arrives
On-site captureinterior floors and areas, RTK-placedOBSERVEDwhat the drone cannot see: interiors, shadows
Satellite priorheight per year, ~4 mINFERREDa hint for floors when nothing better exists
Said plainlyThe GCC GIS layer does not publish declared plinth area, floor count or tax amounts. Until the assessment-register CSV is provided, “declared built-up” is shown as not on register rather than invented.
Chapter 3

How a flight becomes a dossier, with nobody clicking

Flight
images + RTK sidecars
WebODM
orthophoto · DSM · DTM
tilebake
imagery tiles
ndsm-buildings
isolate + measure
dossier
one file per building
  1. 01Photogrammetry produces an orthophoto, a surface model (DSM) and a terrain model (DTM). The epoch is marked READY.
  2. 02nDSM = DSM − DTM. Anything at least 2.5 m tall and 15 m² in area is a building candidate.
  3. 03A candidate that overlaps a register footprint (IoU ≥ 0.3) attaches to it. Otherwise it becomes a new drone-only building, drawn with a dashed edge.
  4. 04Footprint area, roof height and floors are written as OBSERVED with a sigma. Floors are height ÷ 3 m; the storey height is recorded, not hidden.
  5. 05The dossier job runs on exactly those buildings. An unmatched one reads: potential unassessed property, verification required.
Chapter 4

Reading a dossier

Click a building. The panel docks to the side or floats over the map (pin icon). Top to bottom: identity, match state, built-up area, recorded versus observed, connections, ground evidence, variances, priority.

Provenance chipMeans
OFFICIALfrom a government register (GCC, TNEB, GST, cadastral)
OBSERVEDmeasured by a sensor — drone raster, phone scan, RTK fix
DERIVEDcomputed from other fields, with the formula and sigma shown
INFERREDa model or satellite prior — a hint, never a finding
USER ENTEREDtyped by an officer, attributed to them
Match stateMeans
Matchedone tax account, exact key
Probable matchbest available, not confirmed by an exact key
Multiple candidatesmore than one account could be this building
Unmatchedpotential unassessed property — verification required

A variance is raised only when the measured value clears its uncertainty band. Inside the band the dossier says “field verification required” instead of a false-precision flag.

Chapter 5

On-site capture with an RTK base and rover

  1. 01Open Capture on a phone. Take the position from the device or type the rover's fix: lat, lng, fix type (rtk-fixed, rtk-float, dgps, gps), HDOP, base station.
  2. 02Record a walk-around video, or attach a RoomPlan or scan export for interior floor plans.
  3. 03The platform resolves the building by point-in-footprint and links the capture to it.
  4. 04The dossier's Ground evidence section correlates interior floors and areas with the drone measurement: consistent, disagree, or insufficient, with the numbers.
Said plainlyRGB-only 3D reconstruction from video needs a GPU. Without one the job records “engine not available”; interior plans from scan exports parse regardless.
Chapter 6

Who may do what

RoleCan
Ownereverything, including billing and granting owner
Adminmanage members, all data, approve surveys, reveal contacts (audited)
Operatorrun jobs, upload imagery, request and approve surveys, review audit cases
Fieldown audit cases and dossiers, limited to assigned wards; request surveys
Viewerread the map and dossiers

The full capability matrix in Admin › Team is generated from the routes’ own guards, so it cannot say more than the server enforces.

Chapter 7

Requesting fresh imagery

  1. 01Right-click the map → Request survey here.
  2. 02Radius: 0.5 to 50 km around the point, with a live circle and area. The server refuses anything larger.
  3. 03Or draw a polygon: click vertices, click the first one to close, and the request is placed with its area.
  4. 04Requests appear on the Survey requests layer, coloured by status: requested → approved → scheduled → flown. Forward only.
Chapter 8

Rules the platform will not break

  1. 01Never writes to any government register. Findings only.
  2. 02Never shows a number it did not measure or receive. Empty is shown as empty.
  3. 03Every value carries its source and its date. Sorting is by when the data is of, not when it arrived.
  4. 04Names, phones and emails stay behind an officer-initiated case. Contacts live encrypted; a reveal is logged.
  5. 05No model is trained on citizen data. Pretrained and zero-shot only; the officer is the validation gate.