3D scanning in occupational therapy home assessments: what it captures, and when it is worth it

What a scan captures that notes and photos do not

A written record captures what the OT chose to write down. A scan captures the room itself, and three things in particular come back from it that rarely survive in notes.

• Every dimension, not only the ones on the checklist. The report guide lists the measurements most OTs carry into a home, and no written set covers all of them. A scan carries the doorway clear width that was not on the list, the counter height nobody asked about, the distance from the toilet to the wall. When the funder or the contractor asks a question the visit did not anticipate, the answer is already in the record.
• The relationships between things. Notes record "grab bar at 800 mm". A scan records where the toilet is relative to the wall, the door relative to the hallway, the turn from the hall into the bathroom. Those relationships are what decide whether a walker or a wheelchair actually gets through, and they are hard to reconstruct from a list of numbers.
• A walkable record for the people who were not there. The funder's reviewer has never seen the house. The contractor may not see it until the job starts. A 3D model they can move through answers questions that would otherwise mean a second visit or a call back to the client.

The scan does not add a new section to the report. It replaces the reconstruction that fills the afternoon after the visit: re-reading notes to find a height, matching photos to findings, guessing which wall "beside the toilet" meant (where the time goes).

How a phone produces a 3D scan

The LiDAR scanner in the iPad Pro and the iPhone Pro line (both since 2020) sends out a pattern of laser points and times their return, building a three-dimensional map of what is in front of it. A peer-reviewed study of the sensor, published in Scientific Reports in 2021, measured objects above about 10 cm with an absolute accuracy of plus or minus 1 cm, and found precision dropping off for surfaces smaller than that; the useful range of the sensor is roughly 5 m, which is why a room is scanned by walking through it rather than from the doorway (source 2). A centimetre of error is well inside what a grab bar placement or a doorway clearance depends on, and the same study found the sensor performs identically on the iPad and the iPhone.

Since 2022 Apple has shipped RoomPlan, a framework that uses that sensor to recognize the parts of a room while it is being scanned: walls, openings, cabinets, the furniture in it. The output is a parametric floor plan with the dimensions of each component, which can be opened in design tools or turned into a measurement list (source 1). In practice this means the scan does not have to be measured by hand afterwards; the dimensions come out with the model.

Two practical limits are worth knowing before relying on one. Glass and mirrors read poorly to a depth sensor, so a mirrored bathroom cabinet or a glass shower panel will need a manual measurement over the top of the scan, and a scan is a record of the surfaces it could see: the space behind furniture is reconstructed from what the sensor caught, not measured.

When a scan is worth it, and when it is not

The scan takes minutes and the payback is in the afternoon, but not every visit has an afternoon to save. The honest answer is that a scan pays for itself when the report is long, the form is detailed, or someone else has to act on the numbers.

• Worth it: a whole-home assessment for a major modification grant, where the funder's form wants doorway widths, turning spaces and tub heights in its own order; a bathroom conversion, where the contractor needs numbers the OT cannot re-take from the office; a stair lift, where total rise and headroom decide feasibility; an insurer or WCB file, where a reviewer will question the recommendations; or a repeat visit, where a scan from the first visit shows what changed.
• Not worth it: a single grab bar, where a tape measure answers the whole question; a visit with no modifications being planned; or a client who would rather not be scanned, where the consent question settles it immediately. If the time saved on report reconstruction is smaller than the time spent scanning well, the tape measure wins.

The scan does not replace the measurement

The measurement in an OT home assessment is a clinical act: the OT decides what matters for this client, records it, and ties it to the finding and the recommendation. A scan changes where the numbers come from, not who is responsible for them. The dimensions a recommendation depends on should still be checked, the same way an OT checks a number dictated into a note. The scan's real value is the opposite of replacement: it lets the OT catch the number that was never taken at all, because the room is there to be measured again after the visit. Professional obligations do not change because the room was scanned rather than photographed: the scan is part of the record, retained like the rest of the documentation, and reviewed and signed off by the OT like everything else that leaves the assessment.

Privacy: a scan of a home is identifying

A floor plan identifies a home, and a home identifies its people. A scan is personal information in the same way the photographs and the notes are, and the same rules apply: the client is told what is being captured and why and can decline, the data is stored where the privacy program says it is stored, and it is not used for anything the client has not agreed to. When a vendor processes the scan, the same questions apply as for any documentation tool: where the data lives, who at the vendor can see it, and whether it trains a model (the nine questions).

Common questions