Photogrammetry is an broad set of techniques that is now often used in combination with laser scanning for the production of high resolution 3d models. At root, photogrammetry involves combining many overlapping photos where the camera position moves (structure from motion) and generating a rich product that may include 3d data or a seamless stitched single image. This workshop focuses on the photogrammetry side (not laser scanning).
Of particular interest to archaeologists are categories that include producing
- models of objects
- models of larger features like architectural structures
- documenting parietal art with high quality photos stiched together as well as producing a model
- 3d terrain data from drone or a pole-mounted camera.
In this workshop we will use AGISoft Metashape Pro and also demonstrate the open source software WebODM (Open Drone Map).
The USGS recommended workflow for Metashape 1.6 is particularly valuable for this scientific photogrammetry approach
Workshop Goals
This workshop will begin with a discussion of photography principles for model capture. Next we will take photos of a object with our Canon EOS6D dSLR using a 50mm lens, CHI scale rulers and a green screen. We'll download the images and begin processing them in AGISoft Metashape 1.85. After some discussion of the workflow, masking, and error reduction, we'll using the Assign Targets and Create Scalebars tools to scale and optimize the image. We'll discuss resources for troubleshooting in Metashape, and how to share the results: exporting steps and how to proceed depending on the goals of the model (e.g., web viewing, terrain analysis, 3d printing, instructional replicas).
We will export the model to PDF and to FBX to import into Sketchfab for sharing online. This replica Colima dog ceramic is an example of a sketchfab model.
Additionally we will discuss drone photogrammetry and briefly view an instance of WebODM.
PDF Export from Metashape is a good way to distribute 3D data to audiences who do not have dedicated 3D software installed.
During the 2023 Workshop we photographed a fuzzy Oski bear statue and this model was exported to 3D PDF (attachment below). Note that Acrobat Reader can open this model but you will likely need to enable support from the 3D PDF.
Resources
AGISoft Metashape Tutorials, KnowledgeBase and User forums
Cultural Heritage Imaging discussion
Youtube (many tutorials but of variable quality)
Digital Photography Cheatsheet PDF (brief overview of ISO / Shutter speed / Aperture relationship)
Introduction to Photogrammetry (2020) by Sasanka Madawalagama. This lengthy presentation is a PDF with 100 slides on the history of orthorectification and drone mapping. Uses Pix4D photogrammetry.
USGS Report on Metashape 1.6 detailed workflow for mapping of coastal environments with UAV images
