Abstract

Documenting tangible cultural heritage using 3D modeling techniques is gradually becoming an indispensable component of archaeological practice. The 3D modeling techniques based on photogrammetry and LiDAR scanning enable high-accuracy and high-realistic reconstruction of sites and ruins, and have been proven a powerful tool for documenting archaeological excavations. However, dynamically documenting an ongoing excavation using these techniques is still considered tedious, time-consuming, expensive, and dependent on expertise. Moreover, the application of 3D modeling techniques in archaeological excavations still faces some technical challenges, such as modeling with multi-source and multi-scale data, fusing local models at different times into a whole, achieving fast modeling while GPU workstations are not available in the field, and evaluating the quality of 3D models. As a result, there are still very few archaeological teams deeply engaged in dynamic documentation with 3D modeling techniques, and traditional drawing sketches and taking photographs still dominate. In these senses, documenting the archaeological excavation at the Yunxian Man site (located in Hubei, China) is an invaluable opportunity for exploration and practice. Archaeologists determined to conduct dynamically documenting at the beginning of the 6th excavation project for the site, and established a rotation system to reconcile physical excavation with digital preservation. Through repeated practice and communication, we proposed a workflow and pursued several new methods to enhance the feasibility of dynamically documenting, and obtained multi-temporal 3D models of the ongoing archaeological excavations. In 2022, the Yunxian Man site unearthed the most intact fossil of hominin cranium from about one million years ago in the Eurasian continent, preserving important and scarce anatomical features of early humans in Asia. As the original taphonomic context of the fossil corroded away during physical excavations, the digital documentation consisting of multi-temporal 3D models serves as permanent original data source in subsequent archaeological research. Moreover, we obtained cross-scale 3D models from geographical environment to archaeological site, excavation area, and cultural remains, and all of these 3D models are in an actual, unified coordinate framework. Thus, we can contribute to multidisciplinary cross-collaborative research through data sharing. Considering that digital documentations serve a great value in archaeological research, this paper focuses on sharing the workflow and methods to facilitate digital preservation for more archaeological projects.

Overview

Method

1. Multi-level Control Network
The main equipment used to set up a multi-level control network includes RTK (Real Time Kinematic) and ETS (Electronic Total Station).
RTK is used to survey the geographic coordinates of GCPs in areas where CORS (Continuously Operating Reference System) signals are available (usually open outdoor areas).
ETS is able to survey geographic coordinates without a CORS signal (usually used indoors), but it requires setting up a station at a point location with known geographic coordinates.
We use Daspatial miniRTK and THINRAD TTS-112R10M ETS in our practice.

2. Data Collection
In practice, we use a DJI M300 UAV carrying a self-developed multi-lens camera named Daspatial Shuangyu 7X Pro to accomplish Aerial Photogrammetry.
In practice, we use a Canon 5D Mark IV DSLR camera to accomplish Close-range Photogrammetry.
In practice, we use a Trimble X7 stationary LiDAR scanner to accomplish Stationary LiDAR Scanning.
In practice, we use a KScan-Magic II handheld LiDAR scanner to accomplish Handheld LiDAR Scanning.

We do not provide links for hardware devices as we do not aim to promote them commercially. You may use similar products instead.

3. Cross-scale Data Fusion 3D Modeling & Multi-source Data Fusion 3D Modeling
In practice, we perform the Cross-scale Data Fusion 3D Modeling and Multi-source Data Fusion 3D Modeling with GET3D, and browse real-world 3D models using DasViewer

4. Fast Cloud-based 3D Modeling
Our team has developed the fast cloud-based modeling technology as DasEarth, an online modeling platform that is open to the public. To perform 3D modeling with it, all we need to do is upload data and stab GCPs, and then the system will automatically generate a 3D model.

5. 4D Model Fusion
Although the method of Multi-temporal 3D Model Fusion is relative complicated, all the steps of it are integrated into the 3D model post-processing software DasMesh and the 3D model viewer software DasViewer.

6. Evaluation Metrics
(1) In practice, we programmed the geometric refinement calculation of 3D models. We will soon develop a free and handy tool in DasViewer to provide this function.
(2) In practice, we use DasMesh (Step 1), Windows Paint (Step 2), DasViewer (Step 3), and Microsoft Excel (Step 4) to achieve the above-mentioned operations. We will soon develop a free and handy tool in DasViewer to provide the functions of Step 2, Step 3 and Step 4.
(3) Please go to this repository (DDAE_Compute_3D_Model_Refinement) to get the relevant code, files and sample data.

Download all the software used in this paper:

Tips:
(1) All the software mentioned above, except Windows Paint and Microsoft Excel, were developed by ourselves. You can click the logo image below to open the introduction page of the software and download it.
(2) DasEarth requires registration. DasViewer is entirely free. Other software may meet license issues when the trial expires. You can email the first author (Send an e-mail to Wenyuan NIU) to get a free license for academic research and cultural heritage preservation purposes.
(3) English versions of all software are being planned, only Chinese versions are available now. We are sorry and will move forward with the English version as soon as possible.

More Results (Continuously updating)

Constrained by a confidentiality agreement, we present a limited number of results in our paper. We will gradually update more results here, and they may not limited to the Yunxian Man site.

Operation Guidance (Continuously updating)

(1) We will update some of the text and video tutorials to help more archaeologists with dynamic documenting when we have enough time. This may not be until after June 2024.
(2) You can email me (Send an e-mail to Wenyuan NIU) if you encounter problems that make it difficult to operationalize the methods in our paper. I will do my best to reply in time and update the solutions to common problems here.

Acknowledgements

This work was supported by the National Key R&D Program of China (No.2020YFC1523003, No.2020YFC1522703).
The website template was borrowed from Michaël Gharbi.