Bulletin of the GSI (Vol.63)
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Hidenori FUJIMURA Abstract “GSI Tiles” are tile-based geospatial information for web maps provided by the Geospatial Information Authority of Japan (GSI) under the standardized terms of use of the Japanese Government. GSI Tiles contain official topographic map data maintained under the Survey Act, and also more than 1,000 layers, covering topographic maps, aerial and satellite images, thematic maps, and disaster information. While these data are typically used for web maps such as the “GSI Maps” run by GSI, they are also available for download, and it has been decided that the same server which is used to run “GSI Maps” is to be used to provide these data for download. To keep the server highly available, an effective synchronization method for GSI Tiles has been developed.
To fulfill this purpose, the concept of “GSI Tile Lists” was proposed. A GSI Tile List contains metadata for the files for a layer of GSI tiles. File paths, modification times (mtime), size, and MD5 message-digests are recorded in a GSI Tile List. The download and synchronization of the GSI Tiles can be made more effective by using a GSI Tile List. GST Tile Lists are updated weekly to reflect the rapid update of the topographic data of GSI. A reference implementation of the GSI Tiles downloader using GSI Tile Lists (qdltc) has been developed and published via a social coding site. A layer of topographic map data covering the whole area of Japan, consisting of 50 million tiles, can be downloaded within around a week. A weekly update of these topographic data, consisting of tens of thousands of tiles, can be downloaded within around 7 hours. . Contents1. Background 2. Challenges 2.1 Technical details 3. GSI Tile List 3.1 The reason GSI Tile List is developed 3.2 Specifications for GSI Tile List 3.3 mokuroku generator 3.4 A viewer for GSI Tile List 4. qdltc – a reference implementation of a downloader 4.1 Filter tiles by checking MD message-digest 4.2 Use of queue 4.3 Backup of old files 4.4 Caching local MD5 message-digest 4.5 Performance 5. Future Directions Yoshihiro Fukuzaki, Kozin Wada, Ryoji Kawabata, Masayoshi Ishimoto, Takahiro Wakasugi Abstract The Geospatial Information Authority of Japan (GSI) started a new project to construct a VGOS (VLBI Global Observing System) station in Japan. Construction of the antenna (radio telescope) is complete, and the necessary equipment (Front-end, Back-end, H-maser, and so on) has been delivered. The name of the new site is the Ishioka Geodetic Observing Station. It is located 16.6 km away from the Tsukuba 32-m antenna. We briefly report on the implementation of the new station, especially the initial receiving performance of the new antenna, and the first geodetic results of VLBI observations carried out after February 2015.
Contents1. Introduction 2. Observing Facilities 2.1 Technical details 3. Site Information 4. Antenna and Front-end 4.1 Antenna 4.2 Front-end 5. Receiving Performance 6. First Geodetic Result 7. Future plan 8. Summary Hiromichi TSUJI, Tomoaki FURUYA, Kazuki SAKAI, Motomu MANDOKORO, Yuki KAMAKARI, Hiromi YAMAO, Tomoo TOYODA, Kiyoshi GOTO, Yuki HATANAKA, Hiroshi MUNEKANE, and Satoshi KAWAMOTO Abstract The Geospatial Information Authority of Japan conducted a research and development project from 2011 to 2014 on the smart use of multi-GNSS signals for more efficient surveying and precise positioning essential in the management of national lands. The project aims to combine signals from various satellite positioning systems, such as GPS, QZSS, GLONASS, and Galileo, collectively called GNSS, to achieve centimeter-level positional accuracy in a short period of time, especially in urban or mountainous areas where satellite visibility is limited. Four years of effort on the smart use of multi-GNSS signals by the General Technical Development Funds of the Ministry of Land, Infrastructure, Transport and Tourism yielded technical outputs such as
1) Methods to handle between-receiver biases to combine multi-GNSS signals, 2) Open source software for multi-GNSS surveying named GSILIB, 3) A draft manual of multi-GNSS surveying applicable to public surveys in Japan. This paper overviews the project and focuses on major technical outputs. Contents1. Introduction 2. Project 2.1 Objective 2.2 Framework 2.3 Implementation 3. Outcomes 3.1 Methods to handle new frequency L5 3.2 Methods to combine multi-GNSS signals 3.2.1 Time and coordinate system 3.2.2 Inter frequency biases for GLONASS 3.2.3 Quarter cycle shift in L2C for GPS and QZSS 3.2.4 Inter system biases between multi-GNSS 3.2.5 Half cycle shift for BeiDou 3.3 Open source multi-GNSS analysis software: GSILIB 3.4 Application of PPP for GEONET deformation monitoring 3.5 Draft manual of multi-GNSS surveying for public surveys 4. Future works 5. Conclusions Noriyuki TAKAKUWA Abstract The GSI has archives of aerial photos taken from the pre-war era to the present which are available to the public. Regarding old photos that were taken up to 1974, individual photos cannot be viewed by superimposing them on maps, so it has been difficult to specify such things as locations of photographed objects.
Therefore, utilizing recent advanced image processing techniques, a method has been examined for joining these photos in a simple and easy manner over a wide area and convert them into tile-based dataset so that they can be superimposed on GSI maps. Furthermore, using this method, aerial photos that were taken by the US Army after the war (hereafter, “US Army photos”) of urban areas (mostly urban cores) designated by the government were converted into tiles. This enabled comparisons to be made with photos taken from 1974 on that were already publicly available on the GSI Maps (http://maps.gsi.go.jp/), which are Web-based maps provided by GSI on the Internet, and it was apparently possible to see changes in land use in a time series. In the future, efforts will be made to convert aerial photos taken during the time of the Japanese Imperial Land Survey into tiles using this method, and expand tile-based datasets of past aerial photographs. Contents1. Introduction 2. Orthographic projection 2.1 Bundle block adjustment software 2.2 Issues with orthographic projection 2.2.1 Automatic acquisition of tie points and pass points 2.2.2 Effect of flying conditions on aerial photographs 2.2.3 Artifacts 3. Panorama method 4. US Army photos that were used in this study 5. Geometric conversion 5.1 Selection of reference points 6. Removal of edges 7. Tile conversion 8. Topic for future examination 9. Concluding remarks Akira SASAGAWA, Nobuyuki WATANABE, Kentaro TERASHIMA and Yoshiyuki MIZUTA Abstract Mountain trails, defined as one of the acquired feature items of the Digital Japan Basic Map, have been investigated locally where changes were pointed out by users such as climbers, because of the difficulty of extracting changes from aerial photographs. Since fiscal 2012, the Geospatial Information Authority of Japan (GSI) has started a new approach to investigate them with regional partnerships such as relevant local agencies and volunteers. This approach enables us to reflect the latest mountain trails on a wide area of the target mountains on the Digital Japan Basic Map. We report the details of the flow of investigations and the methods of surveying mountain trails with regional partnerships, as well as achievements in 2012 and 2013.
Contents1. Introduction 2. Overview of investigation with regional partnership 3. Review meetings with partner organizations 4. An example of urgent survey of mountain trails investigation 5. Field survey 6. Updating Digital Japan Basic Map 7. Conclusions |