In my area, the assessor uploads Apex sketches of floor plans online. The homes here were nearly all built since 2000 and the sketches are very reliable. I'm considering just inserting the assessor pdf into my reports instead of re-sketching and stating that the measurements were confirmed on-site. Is anyone doing this?
MEASUREMENT is fundamental to appraisal. You should take your own measurements, per ANSI or BOMA standards, to the inch and draw architectural type floorplans that show approximate wall thickness. This is fairly easy to do with Chief Architects "Home Designer Pro" or the more expensive "Chief Architect Premier".
I typically do measurements with a tape measure and $500 laser meter.
1. I make too many measurements of the interior to use an IPad app for drawing. Green graph paper. Fast and easy. Arrows all over. I can jump out and make a separate sketch of a hall way with exact measurements.
2. Outside first. Measurements to the inch. Doors and windows usually measured from closest corner. Photos as well, in case I miss something.
3. Inside. For each floor, first do a walk through to visualize the layout of all rooms, hallways, entrances. Do a rough sketch to lay down rooms for subsequent measurements. Be cognizant of openings to the upper story and dead spaces, as well as the garage. All measurements to the inch. If you add up the interior width measurements (best if you can do this and avoid interior walls) and subtract from exterior width and divide by two, you get the approx wall thickness. Ext walls are typically 6" or 4" and interior 4". But we have those hidden spaces like around the bathroom where a double wall makes extra room for piping. In very old homes, e.g. in San Francisco, you find larger hidden spaces - for one reason or another. But you can't always see hidden spaces and for this reason, you never want to promise an interior accuracy greater than +/- 6" - which should be good enough, except you must be accurate on anything that goes into calculation of GLA. If you do this right, you will have double arrows all over the place, with foot/inch measurements.
4. When you get back to the office, use Chief Architect to enter the measurements. This goes pretty smoothly as you can add in exterior and interior dimensions and move the walls around to make them match your measurements. You can choose 6" or 4" walls or make them whatever thickness you want. You can't alter the exterior measurements. But you can fudge on the interior if needed, as walls are rarely exactly 6" or 4" or whatever. And, you may have missed some hidden area. You invariably find some problems that have to be solved (and this is when you wish you had over measured or double measured a bit more.)
With experience you will find this becomes easier. But I have to warn, 125+ year old triplexes in San Francisco that have had dozens of improvements over their lifetime, complex room layout, hidden spaces and the like, will put your powers of visualization, recording and measurement to real test.
https://www.homedesignersoftware.com/videos/overview/pro (choose "Walls-Rooms" for a good video)
https://www.homedesignersoftware.com/
https://www.chiefarchitect.com/
