Advancement through Consolidation

The last half of the 20th century saw remarkable technical innovations in the field of surveying in general, and survey engineering in particular. These innovations, initially the tools of the geodesist, eventually became common among land surveyors, bringing geodetic quality measurements to surveys of ordinary extent. The first innovation was the electronic distance-measuring instrument (EDMI). The first commercially available EDMI, the Geodimeter NASM-2, was introduced in 1950. The advent of the EDMI freed the surveyor from physically traversing the ground he measured. Twenty years later, in 1971, the combination of EDMI and theodolite, in the form of the Geodimeter 700 and the Zeiss Reg Elta, created the total station. The eventual coupling of the total station and field computer completed the modern data collection system almost universally employed by the modern surveyor. In 1990, Geodimeter introduced the first robotic total station, the System 4000. The final step in the evolution of the 20th century total station was the reflectorless EDMI. The first coaxially mounted reflectorless total station, the Leica TPS 300/1100 was introduced in 1998.

More liberating to the surveyor was the introduction of the Global Positioning System (GPS). Even before reaching full operational capacity in 1995, GPS removed the requirement for line of sight that remained with EDMI. With GPS, the only physical constraint for measuring is a view of the sky. GPS has redefined the way surveyors access the National Spatial Reference System (NSRS). Following the original paradigm of physically monumented networks, more accurate networks were created using GPS observations. Known as High Accuracy Reference Networks (HARN), these networks upgraded the accuracy of the North American Datum of 1983 (NAD83). GPS observations on the HARN began in 1986 and were originally completed in 1997. Even before the completion of the HARN, the first Continuously Operating Reference Station (CORS) was established in 1994. By the end of the 20th century, over 200 CORS were operating in 48 States. The CORS network has continued to expand and currently over 900 CORS sites operate in North and Central America and the Caribbean.

Paralleling these innovations in measurement technology are equally rapid advances in communication. The Internet and email have forever changed how information is disseminated. Information is available over the internet on demand.

Since the turn of the century, these tools have continued to mature; the range of reflectorless total stations has increased; and improved GPS receiver and antenna designs have decreased multipath and increased tracking ability. However, the innovative trend is toward a consolidation of existing technologies. Surveying technologies are merging in synergistic combinations that augment and enhance their efficacy. Surveyors have never been able to rely on any single technology alone; but new tools that combine several complementing technologies blur the difference between surveying methods and allow surveyors to complete projects with greater efficiency and better results.

The Online Positioning User Service (OPUS) introduced by the National Geodetic Survey (NGS) in 2002 is a convergence of Internet-based communications and the CORS network. Using OPUS, surveyors can submit their dual frequency GPS observations to the NGS via an internet-based portal, and receive computed NAD83 (CORS96) and International Terrestrial Reference Frame 2000 (ITRF00) coordinates of the occupied station along with quality control information, by email. Initially viewed as potential competition by surveyors providing control to clients, OPUS has forever changed the way surveyors access the NSRS. OPUS continues to evolve, spawning two new flavors. Best results are obtained from the original OPUS with observation sessions greater than two hours. OPUS Rapid Static (OPUS-RS) can produce results with as little as 15 minutes of data. OPUS Data Base (OPUS-DB) allows users to share their OPUS results through the NGS Integrated Data Base (NGSIDB). Using OPUS, geodetic quality control is available on demand through the Internet.

A more intimate fusion of Internet-based communication and CORS GPS are the Real-Time Kinematic (RTK) networks deployed by private and government organizations. These networks broadcast GPS observations and corrections over the Internet. Network RTK eliminates the need for a dedicated GPS receiver acting as a fixed base station and extends the working area. Subscribers log into the data network using an IP address through a cellular modem. Leica GPS Spider (Leica Geosystems, Norcross, Ga.) and Trimble RTK Net (Trimble Navigation, Sunnyvale, Calif.) provide regional RTK network software solutions. Leica GPS Spider offers network solutions based on Zero-Difference Processing while Trimble RTK Net offers Virtual Reference Station solutions. Briefly, Zero-Difference Processing estimates the satellite and receiver clock errors along with the station coordinates and zenith total delays. The Virtual Reference Station solution broadcasts corrections simulating a reference station very close to the position of the roving receiver. The short baseline between the virtual base station and the roving receiver eliminates distance dependent error sources in RTK vectors. With Network RTK GPS, extensive surveys are possible with one-person field crews.

At the federal level, the NGS is considering the possibility of streaming GPS data, but not corrections, via the Internet, from select federally funded CORS. Using NTRIP [(Network Transport of RTCM via Internet Protocol) RTCM—Radio Technical Commission for Maritime Services], a stream of GPS observation data will be publicly available and free of direct-user fees. It is hoped that providing this data will enable other entities to provide location-based services relative to the NSRS. As more GPS users migrate from post-processed to real-time positioning, this union of CORS data and Internet communication will become more vital.

Originally built as a cold war competitor to the US NAVSTAR GPS (NAVSTAR—Navigation Signal Timing and Ranging), the Russian GLONASS system is now complementing GPS surveying systems by providing additional satellites. In the 1990s, Dr. Javad Ashjaee developed Ashtech’s first dual constellation single frequency receiver. Early reliability and accuracy questions slowed the commercial acceptance of GLONASS as an equal partner in Global Navigation Satellite Systems (GNSS). Dr. Ashjaee left Ashtech to form Javad Positioning Systems, which was subsequently acquired by Topcon in 2000. With this acquisition, Topcon gained considerable engineering acumen in GPS/GLONASS receiver technology and signal processing. The success of the TOPCON Hiper Pro (TOPCON Positioning Systems, Livermore, Calif.) line of GNSS receivers prompted both Trimble and Leica to introduce GNSS surveying systems that utilize all the navigation satellites in view. Integrating GLONASS and GPS increases productivity by reducing the impact of obstructions and low DOP values.

The marriage of the reflectorless EDMI and servo-driven robotic total station gave birth to the 3D engineering scanner. Leica Geosystems acquired Crya Technologies in 2001 and introduced its High Definition Surveying (HDS) scanner. The following year, Trimble Navigation introduced their 3D scanner from Callidus Precision Systems GmbH. Applications of 3D engineering scanners range from detailed record drawings of architectural features, which previously required the use of terrestrial photogrammetry, to more mundane topographic surveys, where they function as autonomous total stations. By systematically measuring millions of points per setup, creating a cloud of points, engineering scanners produce a complete and detailed record of existing conditions. By measuring without a reflector, engineering scanners locate details without the need to enter dangerous situations such as traffic or high spaces. The accompanying software can remove intermittent obstructions such as passing pedestrians and cars, reduce delays in the field and allow work in active environments. The reduction software allows the surveyor to produce conventional deliverables from the cloud of points these scanners produce.

Complementing the horizontal accuracy of RTK GPS with the vertical accuracy of a rotating laser level, TOPCON Positioning Systems introduced the Millimeter GPS System at the 2004 ACSM Convention (ACSM—American Congress of Surveying and Mapping). With one laser, the Millimeter GPS System has a vertical range of 33 feet and can cover a circle with a diameter of 1000 feet. Four units can be ganged together to extend the working area to a mile and a half. With this hybrid technology system, TOPCON seeks to replace robotic total stations for construction stakeout.

Leica Smart Station further blurs the difference between spatial and terrestrial measuring methods with its inosculation of total station and GPS in one instrument. The Leica Smart Station combines the TPS1200 total station with an ATX1230 Smart Antenna. The ATX1230 is a dual frequency RTK GPS receiver. Mounted above the total station, the ATX1230 communicates directly with the total station. In this configuration, the Leica Smart Station can establish its own position with RTK GPS, including Network RTK, while using optical methods to locate objects in areas where the view of the sky is obstructed. The software controlling the Smart Station obscures the distinction between optical total station and GPS operation. The Leica Geo Office software further integrates GPS, optical total station and leveling data into a unified database for processing and export to other applications.

On the construction site, the integration of surveying technology with grading machines for machine control is becoming more common. Rotating lasers, robotic total stations and RTK GPS can control site grading in a stakeless construction environment. While this trend may seem to reduce the role of the surveyor on the construction site, the surveyor with his understanding of topography and terrain models is ideally poised to market his knowledge to site contractors. The surveyor is the professional most qualified to identify the parameters upon which the site grading depends and to develop the terrain models that drive the blades on the graders. This model of construction emphasizes the surveyor’s role as data provider rather than a measuring technician and laborer.

With their acquisition of Spectra Precision in 2000, Trimble complemented their GPS expertise with innovative technology from Geodimeter and Zeiss. By bringing together the company that introduced the first commercial EDM, Geodimeter, with the company most responsible for making GPS the utility it is for the practicing surveyor, this acquisition brought full circle the convergence of surveying technologies. The immediate result of the merger of Spectra Precision was the Trimble Toolbox with its Integrated $\mathrm{Surveying}$ paradigm. This convergence of terrestrial surveying and GPS surveying is accomplished through the unified data collector and software. The emphasis here is on acquiring the positioning data or laying out predetermined positions, not on the measuring method. The surveyor chooses the most appropriate measuring tool for the task; the data collector organizes and records the data; office software processes the observations, be they GPS vectors or total station angles and distances. This coalescence of data, independent of the method of collection, is the model for the synergies that result from the merging of technologies.

The common goal of the convergence of these disparate technologies is to move surveying away from a measurement-oriented profession to a data-centric profession. As sophisticated, multi-technology tools allow the acquisition of more information, the surveyor’s role is increasingly developing to organize and direct the flow of that data. Understanding how the surveyor’s data contribute to the success of the enterprise is the indicator by which the professionalism of the surveyor will be measured in this new surveying environment.