Scale Models

A project log for Photogrammetry and Image Acquisition

An exploration into image acquisition techniques and its effects on the quality of 3D models using Pix4D Mapper Pro software.

travis-broadhurstTravis Broadhurst 07/11/2016 at 11:530 Comments

One commercial application of 3D modeling is creating scale models of different areas. This has largely been used in the construction industry to create a model of a house, map a work site, measure the amount of gravel in a stockpile without having to use heavy machinery to otherwise do so, etc. However, I thought that it could also be used to provide a reference for models of smaller size, such as the sharktooth or historical artifacts. Additionally, Pix4D Mapper Pro reports a parameter that counts the density of triangles in the mesh per cubic meter. This is a perfect measurement of the precision of the finished model, as a higher number of triangles per cubic meter denotes a much more exact model and can show more detail. However, this is not an accurate measurement if the scale is not included and the model is not calibrated to that scale.

In order to best create scale models, I would include a meter stick in the photos and create the model fro these photos just like any other model. I would then create manual tie points in the Pix4D Mapper Pro software, add a scale constraint, and reoptimize the project. This gave amazing results, and allowed for measurement of any other item or length in the project. Surface areas and volumes can also be reliably and accurately calculated in a scaled model. The only concern with this method was that the meter stick would be in the final model. So, to avoid this, I would create the model and then measure the distance between two definite points with the meterstick to add the scale constraint without having to include the meterstick in the model. This was done in subsequent trials and models to have an accurate measurement of the density of triangles in the mesh. After many trials and attempts, I was eventually able to use the scale constraint and measure items in the model to an accuracy of half a centimeter.

The commercial application of this practice to approximate materials needed to extend the roof of a biergarten in Konstanz is awaiting third party permissions.

Thank you.