The United States, Canada, Australia and other countries have started a new round of national geological mapping plans since the mid-1980s. For example, the national geological mapping plan in the United States, the national geological mapping agreement in Australia and the energy and mineral geological mapping plan in Canada all have a common feature, that is, the general goal of establishing a national geological mapping database is put forward, and the use of geographic information system (GIS) to manage geological information and develop and establish a digital mapping system network is an important technical way to improve the ability to meet the needs of different users.
At present, the application of information technology in field mapping varies greatly from country to country. The United States and other countries are still in the exploration stage, while Australia has achieved a complete production process from field data collection, database construction, GIS comprehensive analysis to auxiliary mapping publishing. This section mainly introduces the digital mapping technology of field data collection and final geological map informatization in the United States, Canada and Australia.
1. Application of information technology in field data acquisition
In the past, geologists usually recorded field observations, sketches, survey data and descriptions in field record books. These recording methods are still valid at present. However, with the increase of digital photos in the field and the use of GPS and other technologies, in the past 10 years, the work of field recording and data collation by using field digital acquisition system has increased dramatically.
1. American field data collection
Digitization of field geological data collection is the general trend of geological mapping in modern countries, but the specific working mode has its own characteristics. In order to meet the surveying and mapping needs of "geological phenomena guide geological routes" and improve the efficiency of field work, the United States mainly adopts the working mode of field data collection and digital separation. Field surveying and mapping consists of surveying and mapping experts and auxiliary personnel. The former is mainly an employee of the US Geological Survey, who is responsible for completing geological mapping. When mapping in the field, use cards to record the field and outline geological phenomena. The latter are mainly students hired from universities or graduate students brought by surveying and mapping experts themselves. They are responsible for digitizing the geological data in the notebooks of surveying and mapping experts in the field camp (Figure 6- 14).
Figure 6- 14 Digitization of American Field Data
(According to Athey et al., 2008)
The mapping group with Kellogg, an American geological mapping expert, as the chief scientist is a typical example. In recent years, they have successively completed more than 24,000 geological maps of bedrock mountain areas in the western United States 1∶ 100000 and1∶ When completing a 1∶24000 geological mapping in Colorado, Kellogg was in charge of mapping, Tai Sen was an assistant in field mapping, Yang and Brandt were in charge of digitizing field data, Bill Sawers was in charge of designing digital geological maps, and Nancy Shock prepared GIS files of digital geological maps.
At the same time, the United States is constantly trying to change from traditional mapping to digital mapping on the premise of ensuring the quality of the field. For example, Athey et al. (2007) in Alaska, USA, used field digital mapping equipment to carry out field mapping experiments (Figure 6- 15). The geological mapping of bedrock 1∶24000 carried out by USGS in New Hampshire 1998 shows that its mapping technology is relatively mature. In the process of drawing, PDA3Com Palm is selected to run Pendragon table data acquisition software with version 1.2. The system uses Palm OS handheld operating system, which only records spatial location and attribute information, so it uses PDA and uses some database functions of Microsoft Access of Windows 95, 98 or NT system. The table can be generated by Pendragon table, Microsoft Excel or any ASCⅱII II text editor, and then converted into Palm Pilot format. Users can flexibly use their favorite and familiar software or specific data fields. Once the table matching the data model is completed, attribute data and point data can be collected on any outcrop in the field through PDA and GPS. After the field work is completed or when drawing is needed, Microsoft Access data can be converted into Arc/Info point layer (Jiang Zuoqin et al., 200 1).
At present, the geological mapping work of the US Geological Survey is full of vitality and fruitful results. Satellite images, aerial photography, GPS technology and GIS-based mapping technology provide technical support for the mapping work. However, all geological mapping is ultimately attributed to geologists, who walk on the ground with boots, compasses, notebooks and magnifying glasses, just like Powell's time.
Figure 6- 15 Alaska field digital mapping equipment
(According to Athey et al., 2008)
2. Field data collection in Canada
1984, the Geological Survey of Ontario, Canada, carried out a computerized research on the whole process from field sketch to publication of color maps. 1989, the Geological Survey of Ontario, Canada developed a "field log" to help geologists manage field geological data, and the Geological Survey of Canada further developed this log (Brodaric et al., 1997). 1990, geologists began to study regional survey automation. They store the base map data purchased from the government in a portable computer, and add the observation information recorded in the notebook to the digital base map every night, so as to draw sketches in the wild. The success of this research has changed the traditional working mode and greatly accelerated the speed of surveying and mapping.
From 199 1, the "Fieldlog" of field geological data has been applied to regional geological mapping and rapid digital geological mapping in Canada. This technology can also be used in harsh natural environment, and it is also very durable, and can provide complete digital maps and related information in the field. Because it has the functions of recording, storing, displaying and analyzing field observation data in digital form, and assisting graphic preparation and geological interpretation, it can help geologists to digitally manage field geological observation data. Fieldlog is actually a software for indoor collation of field data, and the system has also been adopted by the Geological Survey of Canada.
The "field record" of the field geological mapping system has the following characteristics:
(1) This software mainly uses the relational database in AutoCAD environment, and can be connected with various GIS systems. Project database, graphic representation method, geological glossary, etc. It is completely established in accordance with the conventional geological mapping method, which enhances the functions of database and graphic operation and is convenient for field reference or creation of field geological mapping database;
(2) It has powerful data input function. In the preparation stage of field work, digital geographic base maps, aerial photos or other related data can be input into the field geological mapping database. Geometric shapes (points, lines, polygons) and graphics (such as symbols, characters, lines, etc.) observed in the field work stage. ) can be added to the database and connected to one or more AutoCAD drawings, while lines and polygons must be added through AutoCAD standard graphics function first and then connected to the database, that is, observation of points, structural measurement parameters, rock type characteristics, etc. It can be recorded directly by field recording software and can touch the boundary line.
(3) It has powerful database query function. Using the visual interface to query, users can query the database purposefully and view the results in tabular form. These results can also be output as AutoCAD graphics with common geological map symbols. The supported query output forms include text file and table form, which can be directly converted into GIS system by using conversion tools such as Arc/InfO-Arcview, Mapinfo and SPANS TBA format.
(4) Support multiple operating platforms. The "field record" software is generally operated in AutoCAD graphic environment, which increases the operation ability of geographical and geological processes. The ability to freely develop the environment and operate a variety of hardware and system platforms, so the field recording software can be used in DOS, Windows3. 1, nt and AutoCAD release 12, and can also be used in various database systems such as dBase, ODBC and Oracle, which is easy for users to obtain.
(5) Support various input devices. Version 3.0 of "Field Record" software developed the pen input technology provided by Apple Newton, exported the field database structure to Newton, and used it to input the collected data. You can also input field data from mobile devices (such as GPS, PDA or other devices).
In the process of mapping in the field, geologists can digitize points and geological features from topographic maps and aerial photographs, or use GPS to obtain geographical positions and features, and then record data with handheld computers outside the field (at the same time, they can also use traditional notebooks), and then visualize the data with drawing and analysis tools to interpret and edit geological maps. The final product is formed indoors through a series of editing and drawing processes. The final product can be released in three forms: traditional paper media, ROMS discs and the Internet.
Three-dimensional geographic information system is a new technology of three-dimensional spatial display and data analysis. In the past, the application of three-dimensional geographic information system in earth science was mainly in oil exploration, mining, meteorology, environmental detection, scenic spot construction and geological model. At present, Canada has expanded the 3-D GIS toolkit through further research and development, and has made important progress in data rewriting, projection and surface editing technology after being tested by the Canadian geological mapping project. Today's three-dimensional geographic information system enables the visualization and modeling of three-dimensional geological conditions that could only be imagined in the past. In the process of geological mapping, geologists use three-dimensional GIS technology to generate complex geological visualization images near the surface, which increases their understanding of near-surface and surface observation and measurement results. Combined with GPS and radar satellite images, geological disasters such as landslides can be quantitatively analyzed, displayed and predicted, and a three-dimensional geological disaster prediction map can be generated.
The key to the success of geological mapping or exploration projects is whether a large amount of data can be effectively managed and processed. At present, Canada has developed a geological mapping system, which can store spatial data collected, interpreted and published in the field, and archive, operate, process, analyze and visualize these data through tools provided by GIS technology. In this way, GIS has changed the traditional concept of geological map. GIS tools can make and innovate non-traditional geological maps at any time as needed, and add useful data at any time.
In addition, Canada has developed user-friendly statistical and expert system tools for data visualization, so these tools and quantitative mathematical methods are used to synthesize geological maps and geophysical images to make geological maps showing new special application fields, such as metallogenic prognosis maps, and have been successful.
3. Australian field data collection
As early as 1984, during the geological mapping of Queensland Geological Survey of Australia 1∶250000, I deeply realized that the traditional field data recording method seriously affected the use efficiency of existing data, and at the same time, I considered how to use modern information technology to quickly retrieve, process and analyze a large amount of information obtained in more detailed second-generation mapping. During the period of 1986, the field data acquisition system REGMAP was successfully tested and used in all geological survey projects in this state. REGMAP uses a standard field record book to divide the data collected by each observation point into three basic data types: observation point information, structure and lithology, and designated record structure. This idea of standard structured notebook was adopted by AGSO of Australian Geological Survey in the national geological mapping protocol, and implemented in 1990. It was integrated with other project achievements such as the whole rock geochemical database to form the structure of the AGSO field geological database OZROX.
This structure is not only the database structure for managing field data, but also the basis for designing standardized forms for field collection. Structured notebook can provide basic information that must be recorded in field observation according to geological model. A large amount of information can be collected from outcrops in the field, which is often the key to explain and understand geological phenomena in specific areas. However, the attention of field geologists is often focused on the description of the targets they are interested in, so when recording the geological characteristics of a site, they often abandon a lot of outcrop information. If the original observation results are recorded, the field description can be reinterpreted under the new model. It is difficult for traditional recording methods to avoid the above problems.
The Australian Geological Survey (AGSO) and Resource Industry Association (RIA) jointly developed the AGSO field data acquisition system (Fieldpad), which runs on Apple Newton PDA. Compared with the Canadian system, the system has the functions of map data display, sketch drawing, real-time positioning and superimposed display with GPS data. Fieldpad is a digital field record book developed on the basis of AGSO structured field record book. It can digitize field data on the spot, without re-digitizing the record book, saving a lot of time (Jiang Zuoqin, 1997).
It is worth noting that although the technology of directly recording observation information with handheld devices in the field is mature, Australia still adopts the working mode of manual recording in the field and computer input indoors (Jiang Zuoqin, 1997).
In short, European and American countries such as the United States, Canada, Australia, etc. are still dominated by traditional field records, and computer technology is mainly used for field data collation and final results release.
Second, computer-aided drawing.
The application and development of digital mapping technology has been widely concerned by all countries. Although digital mapping technology has not yet occupied a dominant position, it has formed a preliminary production process, and digital mapping technology began to enter the practical stage in the 1970s. After years of research, development and experiment, the United States, Britain, Canada, Australia and other countries have incorporated digital mapping technology into the production process.
The new mapping scale of USGS is mainly 1∶24000. In order to adopt digital mapping technology, it is necessary to establish a three-level computer network for projects, departments and regions. The project level is mainly equipped with microcomputers for map editing and input. The department level is equipped with multi-user microcomputers or workstations running UNIX for structural analysis, GIS layering, and multi-project rechecking, and the district level is equipped with minicomputers or high-end microcomputers, scanning input and high-end output equipment for drawing. According to this plan, starting from 1990, 45 project-level workstations will be established every year.
At the headquarters of the US Geological Survey, the production of digital maps has taken shape, and dozens of workstations are running. According to the established standards and specifications, determine the digital content, software and hardware configuration, quality inspection and corresponding production process. The workflow in the United States and Australia is slightly different, but they all include drawing preparation, digital input, editing and modification, database building, sorting, intermediate proofing, color separation and plate making, which is used to produce drawings with good publishing quality, while the printing factory is responsible for plate making (Jiang Zuoqin, 1997), realizing the digitalization of the whole process.
Since 1980s, the social demand for geological data has been increasing day by day, and new methods such as digital technology need to be developed in the field of geosciences to ensure data coordination among Canadian government departments. 1989 upgraded computer equipment to realize the modernization of map production process and assembly line production. GSC Geoscience Information and Communication Office, which is responsible for digital mapping, will store the digital base map data bought from Canada's Ministry of Energy, Mining and Resources, Bureau of Surveying and Remote Sensing and other units, develop relevant interface software, establish the output flow, and make geological maps with publishing quality in the mapping plan. Canada began to implement the national geological mapping plan on 199 1, encouraging all institutions interested in earth science to carry out cooperative projects, especially those that use computer technology the most. Through the cooperation of different geoscience government departments, the mapping of field bedrock and Quaternary geology has been carried out, and digital technology has been applied in various geological mapping, geological mapping and database construction.
Australia has initially formed a complete production process from field data collection, database construction, GIS comprehensive analysis to auxiliary mapping and publishing. In order to compile the second generation map with a new method, determine the field observation position with GPS, establish the workflow of field measurement of magnetic susceptibility and gamma data, and develop a database for recording lithologic characteristics. At present, notebook computers have been used in field work to collect data in a new way, and various databases needed for field observation, outcrop lithology, geological age, rock geochemistry and rock properties have been established. All data are managed by ORACLEDBMS, integrated, superimposed and interactively edited and modified by ARC/INFO until the final version is finalized, and then color separation and screening sheets are generated by large-format high-precision laser imagesetter for plate making and printing. The new process of digital mapping method is studied. The whole process of field data collection, database establishment, comprehensive superposition and drawing and printing is aided by computer. 199 1 ~ 1992 gold mine project has been completed 12 digital geological map 1: 100000. They will gradually replace the traditional manual surveying and mapping with this new technology (Zhang Liangbi et al., 1994).