Knowledge centerThe vocabulary of building documentation.
Plain definitions of the drawing types, file formats and survey methods that come up on every existing conditions project — written for the people who have to read the drawings, not for search engines.
How to use this
Every entry answers one question in plain terms, with the numbers attached where numbers exist. They are written for the people who have to read the drawings: architects working into an existing building, engineers checking whether a route clears, facility teams inheriting a record nobody trusts.
Three of them come up in almost every project, and they are the ones worth reading first: what a 3D laser scanning actually measures, how accurate the result is, and which drawing answers which question. The rest are here because a client asked us and the answer was longer than an email.
What is LiDAR?
The measuring principle behind every laser scanner: a pulse, a travel time, a distance. What a point carries, how many scans become one survey, and what LiDAR cannot do.
Laser scanning vs. photogrammetry
One measures where a surface is, the other calculates it from photographs. Which to use where, how to combine them without losing the tolerance, and three things people get wrong.
Terrestrial vs. mobile mapping
Whether the scanner stands still or walks decides accuracy, throughput and price. Side by side comparison, and why method is chosen per area rather than per building.
USIBD Level of Accuracy
The US specification for stating how accurate documentation is. Measured against represented accuracy, how it differs from LOD, and the four lines that belong in a brief.
Types of architectural drawings
Plans, elevations, sections, details, schedules: which view answers which question, how a set is numbered, and the difference between existing, demolition and new.
What is a reflected ceiling plan?
The sheet where lighting, mechanical, fire protection and finishes all meet. Why it is drawn mirrored, how heights are annotated, and what it deliberately does not show.
Drawing abbreviations
AFF, TYP, UON, VIF and the rest, grouped by what they describe. Including the ones that mean two different things depending on which sheet you are reading.
What is a Matterport?
What the camera produces, what its one percent accuracy means over forty feet, and the questions worth asking before commissioning one.
Frequently asked questions
Who writes these entries?
The people who run the surveys and produce the drawings. Where a figure appears it comes from our own projects or from a published specification, and where a number would be invented we leave it out instead.
Can we reuse this in our own documentation?
Quote it with a link and we have no objection. If you need something explained that is not here, ask: most of these entries started as an answer to a client email.
Where do I start if I have never commissioned a survey?
Read what an existing conditions survey covers, then the accuracy entry. Those two decide most of what a brief needs to say, and the rest is scheduling.
Question we have not covered?
Ask it. If the answer is longer than an email, it usually ends up on this page.