Checklist: commissioning a measured survey properly

Intended use stated

Planning permission drawings, construction drawings, area accounting, prefabrication, CAFM implementation or heritage documentation. Accuracy, level of detail and delivery format follow from the purpose. Without it, every bidder is guessing.

Quantities stated

Gross floor area across all storeys, number of buildings and storeys, number of rooms where known. “About 4,000 m² gross floor area on three storeys, roughly 120 rooms” can be priced; “an office building” cannot.

Defined: inside, outside or both

Are the façade, roof surfaces, external works and terrain included? The exterior survey is a separate work step with its own method, often by drone.

Disciplines specified

Architecture alone, or structure and building services as well? Building services increase the modelling effort considerably, so they should be explicitly included or explicitly excluded.

Accessibility described

Ongoing operation, occupied, shift work or vacant. A night-time survey in a hospital is priced differently from the same area in an empty building.

Level of detail set per discipline, not across the board

“LOD 300” on its own is not an order. The usual and sensible split is architecture and structure at LOD 300, building services at 200 or 250. Ordering everything at 300 across the board means paying for detail in places where nobody uses it.

Permissible deviation and verification method agreed

An as-built model is considered complete when it lies within the agreed tolerance of the point cloud. If this tolerance is not in the contract, acceptance lacks the benchmark both parties can refer to.

Decided: straightened or deformation-true

The standard case is the straightened model with plumb walls and level ceilings. Deformation-true modelling is used where the deformation itself is the information: on listed buildings, in historic roof structures, in structural assessment. It is a separate method with its own effort.

Component list attached

What is not on the list is not modelled. Typical points of dispute: suspended ceilings, downstand beams, shafts, railings, window sills and floor build-ups.

Attributes named per component, with source marking

The scan delivers what is visible. Layer build-up, material behind the surface, year of construction or fire rating come from documents, from opening up a component, or not at all. Ask for the marking: measured, adopted or assumed. A model in which everything looks equally certain is more dangerous than one with honest gaps.

Deliverables listed individually

Point cloud, 2D drawing set with floor plans, sections and elevations, as-built model, room book, area schedule, virtual tour. Each item separately, because each has its own effort.

Formats stated per deliverable

Model native in the target system, i.e. RVT for Revit or PLN for ArchiCAD, plus IFC. Drawings as DWG and PDF, room book as Excel, point cloud as E57 and, on request, as RCP for Autodesk ReCap. IFC alone is rarely enough, because parameters are lost in the exchange.

Coordinate system and height datum specified

Local system or official reference in ETRS89 with UTM projection and heights in DHHN2016. For anything that will later be updated or merged with neighbouring data, the official reference pays off from the start. Fitting it in afterwards takes more effort than measuring correctly in the first place.

CAD guideline attached, if available

Layer structure, title block, scale, labelling rules and sheet sizes. If no guideline exists, specify whether drawings are to follow our standard. Both work, but restructuring afterwards costs money.

Area standards named

DIN 277 for floor areas, plus the German Living Space Ordinance (WoFlV) for residential property and MF-GIF for commercial lettable areas. Which area applies to what should be settled before calculating, not when the bill arrives.

Sample delivery agreed before the series

For several properties: one building in advance, producing a sample drawing and a trial model, then sign-off of title block, layers and attributes. An error on one property is a correction; the same error across forty properties is a project of its own.

Rights of use for point cloud and model settled

The point cloud is the asset: years later, new analyses can be derived from it without anyone going back on site. Get unrestricted use in writing, including passing it on to other project participants.

Archiving and availability clarified

Who keeps the raw data, for how long, and how will you get at it in five years? The point cloud of a building quickly reaches double-digit gigabytes; this is not a matter for a file attachment.

Handling of inaccessible areas agreed

See Checklist 01: follow-up capture, adoption from documents, or omission with a note. The rule belongs in the contract, not in the acceptance record.

Schedule with intermediate steps

Survey, point cloud, sample delivery, complete delivery. The survey is the smaller part; the time goes into processing. A realistic schedule lists both separately.

Contact persons named on both sides

One person per side who makes binding decisions on queries. Technical queries during modelling are normal. If they wait two weeks for an answer, the project stalls.