Optimal Ranging Introduces the Spar, One-step Subsurface Utility Locator and Mapper
July 5, 2011
Optimal Ranging, Inc, (ORI) today introduced the Spar, a handheld, one-pass, remote sensor capable of locating and GIS mapping in 3-D subsurface cable, conduit and pipe with up to centimeter-level accuracy to depths of one meter, decimeter-level accuracy to depths of three meters and sub-meter accuracy to depths of 15 meters. The new method is expected to be of interest to surveyors and GIS professionals who are looking to incorporate underground surveys in their work. The Spar operates similarly to a GNSS receiver by incorporating additional sensors just as the GNSS receiver makes use of additional satellites. The unprecedented performance of the Spar is made possible by ORI’s proprietary FieldSens remote sensing technology integrated with GNSS-derived geographic positions. The Spar determines the offset and depth of the pipe and automatically merges it with the GNSS geographic position to produce a survey-grade subsurface 3-D map, with estimates of both horizontal and vertical RMS error, in GIS or CAD formats for export
Easy to Operate
To locate and begin mapping, the Spar only needs to be brought in proximity to the utility line. It automatically displays the location of the utility on the GIS map interface and guides the operator along the lay line of the utility. The Spar identifies the position of the utility regardless of its orientation to the radiated field, which allows the operator to follow the track even when the utility is behind a fence or covered by impassable vegetation.
Broad Range of Applications
Handheld, pole or cart-mounted, the Spar is designed to meet a broad range of applications. Depending on the job requirements, either a single Spar or dual Spars may be integrated with several levels of GNSS (global navigation satellite system) positioning accuracy. For entry-level applications to depths of three meters requiring decimeter-level accuracy, a single Spar with single L1 frequency GNSS geo-positioning is suitable. For applications requiring centimeter level accuracy or to depths beyond three meters, a dual Spar configuration and dual-frequency, multi-constellation GNSS is recommended.
NTT Field Tested
In field tests using five pre-production units, Nippon Telegraph and Telephone (NTT) Infrastructure Technology, a division of NTT, reports the Spar uniquely delivers the required reliable accuracy. According to Toyokazu Fukui, R&D Group Director, their previous underground cable mapping process was only successful down to 1.5 meters. “The Spar delivers reliable five percent accuracy down to three meters, and because of its forgiving ease-of-use we have been able to improve our mapping efficiency,” said Fukui. The NTT R&D Group tested the Spar on a variety of lines including fiber optic, metallic telephone and even water mains. The Spar results are so positive; NTT is moving to expand this service capability to offer locating and mapping services to municipalities, water companies and other utilities.
The Spar Surpasses Conventional Locating in Four Key Ways
1. The Spar measures offset as well as depth, eliminating the need to bring the measurement equipment to specific points related to the utility cable or pipe in order to validate position. Legacy instruments must find the peak or null in the signal in order to confirm pipeline or cable position. The Spar needs only to be in the approximate vicinity to calculate position.
2. With every 3-D position at up to a five positions per second rate, the Spar provides an estimate of the expected error in the position of the underground targeted utility. Associating RMS error to GNSS receiver derived positions has long been essential to understanding the quality of aboveground geospatial data. Now, with the introduction of the Spar, the same understanding of accuracy can be known for the underground component of the geospatial data.
3. Two spars can collaborate on the job site through a wireless network, resulting in a doubling of the number of sensors used to position the targeted utility. This directly leads to improved accuracy and reliability, in the same way that an increased number of satellites improves the reliability of GNSS positions. More importantly, wireless networking allows an arbitrary separation distance between the two Spars, resulting in an expansion of the measurement volume compared to a single Spar, thereby giving the two-Spar system improved range and depth performance.
4. A dead reckoning mode is available that holds the measured 3-D position within acceptable tolerances during periods of GNSS signal degradation, such as under foliage cover or beneath underpasses. About the Spar FieldSens Technology
The Spar FieldSens technology is based on the optimization of data from many sensors against a physical model of the magnetic field expected from a utility line. The effects of ground conductivity and field distortions are accommodated in the real-time processing. Using two 3-D magnetic field sensors, a triaxial accelerometer and digital compass, FieldSens identifies the offset, depth, current, and yaw angle to the underground utility regardless of its position in the radiated field. FieldSens need only be in the approximate vicinity to calculate position with corresponding confidence bounds. In combination with GNSS, automatic geo-positioning can occur even from the side of the actual utility. Beyond the convenience offered by the continuous measurement of line offset and depth from an arbitrary point in the field, the method effectively deals with field distortion, one of the biggest problems of conventional electromagnetic line location.
The Spar is available now and ships from stock in several standard configurations. Custom configurations are also available. Price and GNSS options are available from authorized Optimal Ranging representatives. For a Spar datasheet describing features and specifications, please visit: www.optimalranging.com.