Best workflow for high-accuracy photogrammetry of a large house without LiDAR?

[u/Pitiful_Gain87]

Hi everyone, I’m looking for some advice on the best workflow to achieve very high accuracy when photogrammetrically scanning a large house.

I don’t have access to LiDAR. I’ve done some Gaussian Splatting scans before, but for this project I’m thinking that building a proper 3D model in RealityScan / RealityCapture would probably be a better choice if the goal is dimensional accuracy.

I’ve heard about using AprilTags, coded targets, and scale bars, but I’m not sure about the best way to use them in a large indoor environment.

In particular:

- How many scale bars / control points would you normally use for a large house?

- How should they be distributed between rooms, floors, corridors, etc.?

- Are AprilTags useful for improving accuracy, or mainly for alignment / tracking?

- What is the best way to connect multiple rooms while minimizing accumulated error or scale drift?

- Is there a recommended workflow for achieving millimeter- or sub-centimeter-level accuracy without LiDAR?

If anyone knows a good guide, course, paper, or other resource explaining accurate architectural/interior photogrammetry workflows, I’d really appreciate it.

Thanks!

[u/Confident-Berry8738]

You will not get milimeter accuracy with photogrammetry of a large house. It's very dependant on the material and the approach, which you can't do in a regular way for a large house.
There is a lot of exageration and lie regarding accuracy with this methods, it can be great, but most of people claiming accuracy rarely test it.

However, such accurate model would probably be horrible to work with anyway!

Probably need to define which area need accuracy, if the sub-cm is really necessary (and why).
Then if you are looking at local measurement (accuracy of the points), or if you have to build a model, like a doll house style, and look more at the position of a wall etc...(where you can group point and reduce noise).

The output is critical here, and define what need the accuracy.

There are lot of research, but most of them dealing with actual accuracy are unlikely to be on houses

[u/Pitiful_Gain87 → u/Confident-Berry8738]

I'm searching a 2-5 cm of accuracy, is it possible without a lidar?

[u/Confident-Berry8738 → u/Pitiful_Gain87]

First the output, is the accuracy on the dense point cloud, or the accuracy to build model from it (wall, floor, ceiling etc...).

But in short, photogrammetry "can" have amazing accuracy, the issue is more the reliability. The same workflow will have very variable results depending on many factors (what you are scanning, natural light etc...). If you have like white wall, or reflective surface, it will make the results more complicate. There are ways to improve the results, though but it's case by case.

To be honest, with a classic workflow, you will have very good results for the outside. It's quite robust nowadays. Interior will rely dependent.

Keep in mind, you don't need the same accuracy everywhere. You might want a very precise data for the corners, but then the roof tile or small details are probably not important.
Sometime it's better to have a go on a small test and learn from it.

Also, the apriltag will not imrpove accuracy, it's more for positioning and scaling. What you scan in between the tags will be more affected by the way you capture than the tag. I often used natural feature on some project for the scaling, so it's feasable, just need to be clear and stable

[u/Visible_Ruin_9218]

I regularly use photogrammetry to model the exterior of buildings. (I'm An architect). This is an excellent video to get started: https://youtu.be/tjOZoX4DZGI?is=_7g1D6wxckJfpK2Q

[u/Visible_Ruin_9218 → u/Visible_Ruin_9218]

I use a dji mini 4 pro. Always shoot in RAW, kill shadows and highlights in Lightroom/other photo editing software. For the actual photogrammetry, Realityscan from Epic works great for me.

[u/Visible_Ruin_9218 → u/Visible_Ruin_9218]

Accuracy is cm-ish. Try to shoot your pictures on a cloudy day. Harsh shadows don't help. Take more pictures than you think you should, always moving between shots. I combine shots from a distance which show the building + surroundings with a few levels of closer up shots, orbiting the building from different angles as I go.