Compare as-built and as-planned from image data

What as-built vs as-planned means in an image-data workflow

As-built describes the captured or actual condition. As-planned describes the intended condition from CAD, BIM, execution drawings, PV layouts, refurbishment plans or installation documents. The comparison identifies where those two views align and where they diverge.

For Voxelia, this comparison does not start with selling a new drone flight. It starts with processing supplied image data. Roof images, facade photos, site images, detail shots or supplied drone imagery are converted into technical planning data: 3D model, orthophoto, point cloud, CAD derivation, viewer or BIM-oriented reference.

The value appears when deviations are not just visible but usable in the right handoff format. A planner needs different notes than a roofer, solar team, scaffold planner, crane planner or BIM coordinator. The comparison must therefore fit the downstream workflow.

Required data for a reliable comparison

An as-built/as-planned comparison is only as useful as its input data. On the as-built side, sharp and traceable images with enough visibility of the relevant elements matter. On the as-planned side, drawings, CAD files, IFC models, grids, reference dimensions or project coordinates describe the intended state.

Not every project needs the same depth. For PV replanning, a roof model with obstacles, pitch, edge zones and orthophoto may be enough. For architecture or refurbishment, facade references, openings, planes, defects, point clouds or IFC-oriented element references may matter more. For progress and quality review, deviations must be clearly marked and handable to responsible teams.

Comparison layers in a project

The comparison should not be reduced to a single file. In practice, visual review, geometric comparison and structured handoff support each other. The matrix below shows common review layers without generic accuracy promises.

Workflow from supplied images to review package

A useful comparison follows a clear sequence. First, the supported decision is defined. Then image data and plan state are checked, prepared into a shared reference and delivered as a compact review package.

1. 01

   Define purpose and plan state

   Clarify whether the comparison supports PV, refurbishment, architecture, facade measurement, scaffolding, crane planning or BIM coordination.

2. 02

   Sort imagery and references

   Original images, metadata, reference dimensions, drawings, CAD files or IFC models are checked for usability and visible gaps.

3. 03

   Reconstruct actual condition

   Depending on the purpose, the images become a 3D model, orthophoto, point cloud, textured mesh or CAD-oriented as-built base.

4. 04

   Make actual and planned data comparable

   Plan state and as-built data are aligned through scale, orientation, coordinates, grids or local references so specialist teams can review them.

5. 05

   Hand off deviations

   Relevant points are documented as viewer markers, CAD layers, PDF notes, BCF issues or a short review report.

Handoff to CAD, BIM, viewer and planning teams

The handoff determines whether the comparison is usable in daily work. CAD teams need units, origin, layers and readable contours. BIM teams need traceable model context, clear information states and, where useful, coordinatable issues. Execution teams need clear deviation markers with context, not a flood of raw files.

IFC is maintained by buildingSMART as an open standard for BIM data exchange. BCF is relevant for model-based coordination points because comments and issues can be managed separately from the model itself. GeoTIFF is useful for georeferenced raster data when orthophotos continue into GIS or CAD environments. These standards help, but they do not replace project-specific review of the actual data package.

Document limits and responsibility clearly

Image data can make visible surfaces, edges, roof areas, facades and site states very clear. It does not automatically replace every survey, opening-up inspection or structural assessment. Hidden, reflective, too dark or weakly captured areas must remain visible as limitations.

That transparency matters for clients. A comparison should prepare decisions, not create false certainty. Voxelia therefore separates visible as-built reference, modelled interpretation, planning-ready CAD/BIM basis and points that should be checked on site or by specialist planners.