Structure-from-Motion/Multi-View-Stereo, modern photogrammetry that reconstructs a 3D model from many overlapping images, has been used for 3D measurement in various fields, including construction and surveying. This article describes the outline and technical issues of the model reconstruction process by current SfM-MVS, and the research trends that are solving the problems are introduced.
In public surveying using UAV, we will organize and introduce items that should be understood. In particular, it is important to understand the functional characteristics of SfM/MVS software, and I would like to briefly introduce the functions.
The aircraft test field and UAV test site are operated by the JSPRS have been used for the purpose of various accuracy verifications for photogrammetry. Both fields are maintained for applicability in public surveying. On the other hand, there are an increasing number of application examples that are not necessarily limited to accuracy in recent photogrammetry. Therefore, it is expected that the required accuracy will diversify depending on the situation in both fields in the future.
In this report, we introduce the automatic generation method of the naked-eye stereoscopic website that Geospatial Information Authority of Japan is developing. This method enables to generate naked-eye stereoscopic website automatically, using digital stereo images taken from an aircraft. Websites generated by this method enable us to select both the cross-eyed viewing and the parallel viewing. In addition, since the website can be generated in short time, it is expected to be utilized in disaster response, such as confirming landslide area visually in 3D.
Museums are responsible for deploying resources such as specimens and documents to the public for research, education, and recreation. However, there are some limitations in the use of these resources, and wider utilization of them is a challenge. One solution to this problem is the creation of digital replicas of specimens, especially 3D models of them using photogrammetry. This approach will allow us to research specimens with low management costs, to exhibit them from various perspectives, and to use them in fields different from the past, such as art. These can expand the potential of specimens to various fields. Sharing the museum's specimen resources widely with 3D models may provide a new form of museum use.
A fire destroyed the Shuri Castle, an icon of Okinawan culture in Japan on October 31, 2019. I launched a project with a group of people who gathered on social media aiming to collect photographs and videos of the castle along with the memories from the public, and to digitally reconstruct 3D models of the castle so that they can be used as alternative touristic resources. The data has been collected through a website, and more than 80,000 images from 35 countries and regions have been received from about 3,000 unique contributors, half of whom sent their memories.
Accurate measurement of the shape of road surfaces is essential in pavement work. Recently, mobile laser scanning (MLS) systems have been used to facilitate pavement measurement. MLS Systems require an automatic tracking total station (ATTS) and an inertial measurement unit (IMU) for localization. However, a sophisticated IMU is needed to achieve sufficient accuracy with MLS systems, and such an IMU increases the cost associated with the measurement process. In this report, we propose a novel road surface measurement method using mobile cameras and an ATTS. Our proposed method performs accurate estimation of camera poses using few ground control points, which enables low-cost photogrammetry-based measurements. As a result of our experiment, we confirmed that the proposed method can achieve sufficient accuracy for pavement management.
In Japan, towards the Tokyo Olympics and Paralympics, the Japan Sports Agency has been founded, and policies related to training athletes and improving competitiveness are being promoted. To achieve these policies, many researches use AI technology to analyze sports data gathered by video cameras and IoT devices. To make effective use of those data, it is necessary to manage them with a unified time stamp. However, it is difficult to unify the time stamp because these devices are not linked to each other. To solve this problem, the time synchronization is often adopted manually, but it costs a lot of manpower. Therefore, in this research, we firstly organize the problems of time synchronization between video cameras and between video cameras and GNSS device by investigating existing researches. And then, we propose an efficient and highly accurate time synchronization technologies that can solve these problems.
We used Sentinel1 time series data for the years 2017 and 2020 to determine the harvested area and its percentage within the paddy range. We calculated the average values of VH and VV for the sample points in the paddy fields at each scene and examined the changes in position in the VH-VV plane, then found that they followed a certain path. Based on the graphs, we estimated the threshold values for estimating the extent of paddy fields and for the harvested area, respectively, and then estimated the harvested area and paddy area. The results showed that the ratio of harvested area in 2017 was 93% of the paddy area while in 2020 it was 75.5%.