Real Estate Floor Plan Software: What Happens Between Scan and Plan

Every floor plan tool, from a tape measure to real estate floor plan software working on a LiDAR scan, does the same four jobs: it measures distances in the property, puts each measurement in its place, draws the result as walls, doors and rooms, and hands over a plan that someone has to check. The tools differ in how much of that work a machine does. With a tape and a sketch a person does all of it, while a phone app or a LiDAR camera measures and places by itself and leaves much of the drawing to software.

Every Tool Starts by Measuring Distances

With a tape measure, each distance is taken by hand and written down. ANSI Z765, the US standard for a house's square footage, asks for measurements to the nearest inch or tenth of a foot, and it warns that dimensions arrived at by any means other than direct measurement or plans may be inaccurate, and so may the area worked out from them.

A floor plan scanner measures the same distances with light. LiDAR sends out pulses of laser light, records the light a surface reflects back and works out the range from it. Each range, combined with where the instrument was and which way it faced, becomes a point with three coordinates, and together the points form a point cloud, a dense set of points covering every surface the laser reached.

Phones with a LiDAR Scanner do this on a smaller scale. RoomPlan, Apple's own room scanning framework, uses the camera and the LiDAR Scanner on iPhone and iPad Pro models, and in a developer session in 2022 Apple said it works best on a single room of up to 30 by 30 feet (about 9 by 9 metres), with at least 50 lux of light. Full-height mirrors and glass are hard for the sensor, a high ceiling can be beyond its range and very dark surfaces can be hard to scan.

Whatever the device, a scanner set up inside a house records the inside faces of its walls. That suits room dimensions, which ANSI Z765's commentary notes are usually measured between interior finished surfaces. The standard measures a detached house itself to the exterior finished surface of its outside walls, though, and a scan from inside doesn't see that face.

Measurements Only Count Once They Are Placed

A distance is only useful once the tool knows where it was taken from. A survey lidar system ties every range to its own position and orientation, which is what turns a stream of ranges into a point cloud. With a tape, the placing happens by hand on the sketch.

Apple's framework placed rooms one at a time at first: until its 2023 update to RoomPlan, each room scan had its own coordinate system, and rooms stitched together by hand could end up with duplicate walls. Since then an app can keep one coordinate system running across several scans and merge the rooms into one structure.

A scanning camera places each scan by tracking its movement, which works when each scan can see the one before it. Mirrors and reflective surfaces, large open spaces and a camera moved during a scan all make scans harder to line up. A room with no usable scan can't be drawn at all: its dimensions and area are missing, and the property's total is worked out without it.

Turning Points Into Walls, Doors and Rooms

A point cloud is a mass of points, and a floor plan is walls, openings and named rooms, so the next job is recognising one in the other. Apple's framework uses machine learning to detect walls, windows, openings and doors, along with objects such as fireplaces, couches, tables and cabinets, and it exports each one as a component with its dimensions that other software can adjust. Where a person drafts the plan, they make the same calls by eye.

The drawing can also be tidied so it reads well. Giraffe360's listing images, for instance, have their walls adjusted to look clean, so they are no longer the drawing to measure from, while its DXF file is drawn as accurately as the scan allows, without those adjustments.

The walls need one figure that nobody measured. The scan gives the inside face of each outside wall, and an area measured to the exterior needs the outside face as well, so the software adds a wall thickness that it assumes or that someone sets. If the real wall is thicker or thinner than that figure, the exterior total changes, however well every room was measured.

What a Person Still Checks

In the US, Fannie Mae's Selling Guide requires appraisers to follow ANSI Z765, and it says the output of sketching or 3D scanning software must conform to the standard too, so a scanned plan answers to the same rules as one measured with a tape.

Several of those rules turn on how someone reads the house rather than on a measurement: whether a level counts as above grade, whether a room is finished, which spaces belong in the total. Software can make a first call, but Giraffe360's own guidance, for one, says it can't always detect a level that is partly below grade. When two plans of one house disagree, the gap comes either from those calls or from the measuring, and ANSI Z765 sets no tolerance to absorb it.

On the drawing, room names and types start as the software's defaults until someone who has seen the property confirms them, and so do the positions of doors and windows. Any room the capture missed has to be scanned on another visit, because no edit to the plan can supply its measurements.

A Giraffe360 Floor Plan, Stage by Stage

The Giraffe360 camera measures with LiDAR alongside its HDR images, with a scan range of 0.2 to 40 metres and about 1.5 million points a scan. Giraffe360 puts the margin of error for that LiDAR data generally below 1% for points 2 to 10 metres from the camera. It varies with conditions such as reflective surfaces and with how carefully the camera is carried, and maximum precision can be reached but isn't guaranteed.

The scans are then processed remotely, by AI software followed by a final manual quality check based on the AI's suggestions, as the Help Centre describes it. While that runs, a project's Processing tab, where it has one, shows the status of the floor plans separately from the still photos, panoramas and virtual tour, and a content type drops off the list once it is complete.

For the walls, Giraffe360 measures the inside face of the perimeter walls from the point cloud and works out the exterior footprint from a wall thickness. Under the United States area standard it assumes a 6 in exterior wall, the most common thickness, and under Alberta's RMS standard the thickness can be set between 2 and 12 in.

The floor plans arrive with a default label on each room. In the floor plan editor, a room whose purpose is wrong gets the correct Room type, and a custom name of up to 100 characters replaces the label; Import room names in the virtual tour editor then carries the saved names into the tour. Doors and windows come with the plan, and if one is in the wrong place or of the wrong type, Giraffe360's Support team can correct its icon.

Furniture is added by hand: Objects in the editor adds symbols from a library of appliances, furniture, structural and plumbing items and shapes, which you place, size and rotate to show how a room could be arranged. They go only into spaces the plan already has: objects can't draw a missing room, add a staircase or move a wall.