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Surveying technology: Blending measurement and management

New technologies and changing demands are driving a paradigm shift in modern surveying. Rapid technological development extends beyond measurement to include computing, communications and geospatial data mapping.

For millennia, surveyors have fulfilled the need to mark property boundaries, conduct reconnaissance and make maps for planning. As economies and populations grew, surveyors kept up with the increased demands for broader knowledge and higher accuracy. Today, we are witnessing technical advances that affect surveyors in unanticipated ways. The rapid technological advances extend beyond measurement to include computing, communications and geospatial data mapping. These changes have made geographic information more accessible. As a result, society has placed increased importance on accurate, timely and user-friendly geospatial information. To meet the demands, the role of a surveyor is changing rapidly. Far beyond the time-honoured practices of property and construction measurement, surveying has grown to include managing, interpreting, analysing and portraying spatial information. The surveyor must guide geospatial data consumers working in a variety of related disciplines. Through it all, the surveyor must maintain a high level of data integrity.

FROM SUNDIALS TO QUANTUM MECHANICS


Integrated surveying combines robotic total station with RTK GNSS. Results are immediately available in the appropriate coordinate system.

Beginning with the gnomon (a simple stick in the ground), wood and string, surveying instruments evolved to include metal parts for compasses, chains and rods. Telescopes, which required clear glass, came into surveying in the 18th century. Instruments made of these basic materials were used in the great early surveys of the modern era and remained the dominant instrument technologies through the 19th and 20th centuries. Surveying technology witnessed a rapid change in the 1950s, beginning with electronic distance measurement (EDM) based on light and microwaves. By the end of the 20th century, GPS (global positioning system) and GNSS (global navigation satellite system) emerged to play major roles in surveying measurement. Today, GNSS and EDM (with its high-speed offspring LiDAR and laser scanning) are standard equipment for survey positioning. Recent new technologies including digital levels, airborne scanning, digital photogrammetry and remote sensing have also added to the mix.

In spite of the revolutionary advances in measurement and positioning, the most important change has been a surveyor's ability to capture, manage and utilise spatial information. Field computers have become small, rugged and powerful and can be connected to the office by wireless communications. Tools for management, analysis and visualisation have become faster, more flexible and easier to use. These improvements in hardware and software have combined to deliver significant benefits for surveyors and their clients.

Advances in computing technologies have enabled the collection of more complete data, speedier field campaigns and nearly instantaneous data analysis. Software is continuously evolving to furnish more solutions to niche applications. With a focus on acquiring and managing position data, the systems are supplemented by an array of technologies. For example, surveying systems can be coupled with mobile phone and Internet access, cloud computing and Web-based geo-databases. The new data include control data and information, visible, infrared and multi-spectrum imaging, obliquely sensed aerial data, cadastral information and regional mapping products.

The growth of technology has been the catalyst that enabled a surveyor to evolve as well, changing from measurer/interpreter to geo-data manager. In this expanded role, a surveyor can select, gather and combine information and techniques to meet the needs of the entire project while retaining the ability to drill into tiny details. Let's look at some examples.

MODERNISING CADASTRES AND CONSTRUCTION
In the West African country of Burkina Faso, lack of adequate land titling and record systems is a serious problem. With funding from international agencies, Burkina Faso is setting up the geodetic and computing capability needed to develop and support its cadastral information. The country has installed nine permanent GNSS stations to provide the framework for positioning and geospatial data. In neighbouring Benin, field crews use a similar GNSS system to capture cadastral information. In rural areas, handheld GPS receivers measure property and ownership boundaries to an accuracy of 20-30 cm (0.6 to 1.0 ft). For property in higher-value urban areas, survey-grade GNSS receivers collect data to centimeter precision. After checking and analysing by national authorities, the results are loaded into land information systems running under Esri ArcGIS.

In contrast, the cadastral system in Germany is mature and richly populated. Surveyors working at centimetre level collect positions and attributes according to tightly written specifications. Germany's nationwide network of active GNSS stations provides the framework for precise, realtime measurement. The information is processed and delivered to cadastral databases using formats specified by local and regional authorities. To meet these requirements, field software directs surveyors through the workflows needed to ensure that the necessary information is collected with precision in the field.

On the construction site, a surveyor's traditional role consisted of layout and checking for the heavy equipment operators. But with the advent of machine control, a surveyor's function has radically changed. Today, a surveyor's value lies in supporting construction through planning processes used by construction organisations. In his or her role as geo-data manager, the construction site surveyor creates or verifies the digital terrain and design models used by the heavy machines. Additional activities include work to ensure that machines accurately create the desired design, managing onsite communications, monitoring individual machine performance, and providing input into the project's building information model (BIM).

THE PERFECT STORM OF TECHNOLOGY AND CULTURE
The construction activities described above illustrate the breadth of surveying technology and how effectively different systems can interact to share and utilise information. Long before construction begins, surveyors collect information on numerous aspects of the proposed project. Aerial images, ground surveys, cadastral data and information on existing infrastructure are combined into a database along with environmental and other background data. This information is shared with design and decision teams to provide a comprehensive view of the project and its challenges.

For the early project stages, 3D modeling is becoming an important part of the process. It enables quick design and visualisation of the project and its components and reacts rapidly to the changes that commonly occur. 3D models are developed using information from aerial or vehicular mobile mapping systems or from stationary sensors such as total stations and 3D laser scanners. New total stations incorporate digital cameras which streamline the data collection workflow and provide geo-tagged images of job sites and features. When combined with 3D point clouds, the images help produce photorealistic 3D models.

As the project moves to the engineering phase, GNSS, robotic total stations and 3D scanning are used to collect detailed information on existing conditions. In many locations, a construction project will install an active GNSS network to provide a consistent project reference frame for real-time positioning at the centimetre level. These technologies stay on the site through the construction and inspection process and the GNSS network provides benefits to the surrounding community long after construction has ended.

On a large construction project, the most important surveying component is the communications and information management network. Wireless communications connecting workers in the field and office ensures up-to-date information.

TIGHTENING THE LINK BETWEEN SURVEYING AND MAPPING
GIS is a dynamic management tool that provides a geographic framework to manage and utilise data from a host of sources. A surveyor's involvement in GIS is not limited to just collecting measurements. Surveyors also collect and manage attributes about the elements they geo-locate, using sensors and data collection technologies that extend beyond the normal surveying instrumentation. This is a paradigm shift for many surveyors, who necessarily regard position and spatial relationships as primary data. But GIS presents abundant opportunities for a surveyor who understands that future success requires them to be a geospatial data professional. A GIS can contain data management, precision and visualisation functionality needed to support traditional surveying needs. For a surveyor, GIS presents business opportunities that include creating, populating and maintaining a GIS and using it to manage cadastral data and information on the natural and built environment. As the cadastral and survey layers expand and densify, they infuse new levels of accuracy and precision into the GIS depiction of the physical world.

Given the close relationship between surveying and GIS, it comes as no surprise that the tools and techniques are on the converging path. GIS positioning using GNSS – once the realm of post-processed, metre-level precision – now produces decimetre results in real time. Conversely, surveying data collection commonly includes photographs, multiple attributes and ties to external sensors. The convergence of GIS and surveying is moving to include field workflow and individual tasks. Surveying data collectors include built-in cameras, GNSS receivers and other sensors to acquire information used to populate the GIS database. Survey data can also be readily exchanged with mapping systems using SHP or other file formats that have their roots in GIS.

NEW SENSORS, NEW SOLUTIONS
Mobile mapping systems utilise video and LiDAR imaging combined with position data from GNSS and inertial systems. Airborne systems continue to improve as well, with aerial cameras and scanners supported by positioning systems for navigation, flight management and georeferencing. The data from these highspeed, multi-sensor systems are fused and made available to GIS, design and other applications.

In addition to traditional photogrammetry and terrain modeling, information from the mobile systems can be used for feature extraction, asset management and maintenance operations. For example, a railway can use mobile mapping to collect information on the condition of its track, signals and other assets. This information can be used in planning repairs or schedule maintenance. Airborne imaging has taken an important step forward with the emergence of small, unmanned aerial vehicles (UAV) for aerial photography. Using very small, lightweight aircraft flying at low altitudes, the UAV captures high-quality images over small and medium areas. GNSS provides navigation and georeferencing. The images are processed with traditional photogrammetry techniques to produce orthophotos and digital terrain models.


Unmanned aerial systems provide timely, low-cost imagery. Flight plans are pre-programmed and loaded into the autonomous aircraft.

CONCLUSION
The integration of surveying technologies will continue. Integrated survey rovers, which combine GNSS and total station target on a single pole, are already available. Total stations with integrated video technology enable surveyors to see exactly what the instrument sees and to capture georeferenced images for use in photogrammetry and "in-office surveys." Airborne and mobile mapping systems – still early in their technology life cycle – have significant prospects for improvement in hardware and software that will increase integration, functionality and throughput.

In the end, it's a win-win situation for the surveyor and client. As clients become increasingly sophisticated, they drive the surveyor to deliver higher levels of information and analysis. At the same time, the technological advances in acquiring and applying measurements enable surveyors to perform as the geodata managers that their clients and communities require. By selecting and blending sensing and data management technologies, the surveyor can structure an optimal geospatial solution.