Overview of the Digitization Workflow Post Image Acquisition of Apollo Lunar and Antarctic Meteorite Samples using Agisoft Photoscan for the NASA 3D Astromaterials Virtual Samples Collection

The 3D Virtual Astromaterials Samples (3DVAS) Collection is a multi-year funded project to create a digital database of 60 Apollo Lunar and Antarctic Meteorite samples for researchers, educators and the public. After the high-resolution precision photography (HRPP) capture phase, the data are evaluated and processed using unique structure-from-motion photogrammetric techniques in a high-performance modelling software designed to create 3D models from 2D images: Agisoft Photoscan Pro.

Agisoft Photoscan Pro uses image processing algorithms and techniques originating in computer vision to resolve 3D models for accurate and detailed visualization of a subject. The software provides a stepwise process that is tailored per model based on spatial and specular reflectance properties. The process includes: photo alignment, dense point cloud and mesh creation, and finally texture. Photo alignment is dependent on model properties. The HRPP process requires a special rotation platform with calibrated photogrammetric targets, specific distance rotation protocols, and a contrasting background for alignment and scale accuracy. As a result of the HRPP process, alignment will culminate in two mirrored hemispheres that represent the 2D images overlapping to create a 3D model. Each dense point cloud is analyzed with provided statistical measures in a gradual selection process to eliminate outliers. The point cloud is reduced to include only data valuable to the final model. When a precise dense point cloud is achieved, a mesh and texture are applied. Each model is scaled with scale bar accuracies within 100 microns.

Each astromaterials sample has its own intimate process for modelling; there is no standard for the parameters required in the final creation of a high-resolution model. By processing multiple samples, a skill is gained in practice to allow a close definition of the original sample that results in the most detailed reconstruction of the rock shell.

This process completes one-fifth of the 3DVAS protocol for providing accurate digital documentation. Each model shell is merged with Micro XCT data to create a full volumetric sample. All 3DVAS data will be served on NASA's Astromaterials Acquisition and Curation website. A subset of data will be released in 2019 and the 3DVAS Collection launches in 2020.