Saturday in the Park: NJIT Students Survey Branch Brook Lake
On a Saturday in late June, 12 surveying engineering technology (SET) students, one adjunct professor and one faculty professor — all from NJIT — headed to the lower lake in Newark’s Branch Brook Park. Outfitted with a 15-foot Jon boat and a range of high-tech equipment provided by SET industry partners, they were there on a very special mission: to determine the volume of water in the lake for possible future dredging, and measure the volume of algae in the lake for removal.
The students, classmates from the SET 280 summer-semester marine surveying course, designed the survey-line pattern for the boat to traverse the lake, established and transferred survey control from one project component to another, and planned and executed a topographic, bathymetric (underwater topographic) and 3D laser scan survey of the lower lake and the associated surface algae. They split into three crews for the assignment, with one crew of rotating participants collecting sonar data for a hydrographic survey of the lake, another performing the laser scan and the third manning a robotic total station — an electronic/optical device used in surveying. The goal was to gather comprehensive information on the lake’s depth, bed and edges for a seamless dataset.
NJIT’s SET program was approached about doing the project by Todd Hay from Pennoni, a consulting engineering firm that served as the liaison to the Essex County Parks Department for the undertaking, and Dave Eareckson from Matrix New World Engineering, which supplied a single-beam sonar system.
“Todd is on the advisory board for [NJIT’s] School of Applied Engineering and Technology [SAET]. He has become familiar with the SET program in SAET’s Division of Sustainable Technology and the Built Environment,” said Laramie Potts, SET director. “Of particular interest to Todd was the marine surveying course, which includes tidal studies and hydrographic mapping using state-of-the-art equipment. The hydrographic mapping component of the course will serve the interest of the Essex County Parks Department’s concern about the health of Branch Brook Park Lake.”
Process and Results
The Branch Brook Park project highlights two important elements of the SET program: community outreach and industry partnerships. The latter was particularly evident in and vital to the task.
“A project of this scope and magnitude cannot be performed without specialized equipment provided by the program’s industry partners,” Potts stressed.
SET lab instructor Bert Wyness, working with Potts, was responsible for the project’s logistics, which among many details involved arranging such equipment loans. In addition to Matrix lending the sonar system, HYPACK® provided free software that was installed on NJIT laptops for the students to develop hydrographic mapping solutions; Van Note-Harvey Associates provided a Leica P50 digital high-resolution scanner; Kennon Surveying Services provided and delivered the Jon boat to the site, enabling students to conduct a hydroacoustic survey of the lake; and Leica Geosystems, through its loaner program with the SET program, provided state-of-the-art GPS and robotic total stations along with data processing software.
“Sonar systems rely on digital electrical energy being converted to physical pulsating waves at a transducer mounted just under the water’s surface. In this instance, the transducer was mounted on a pole on the side of the Jon boat. The resulting sound waves, or sonar pulses, travel through the water column, interact with the lake bottom and return to the transducer, which in turn converts the physical energy back into digital electrical pulses that are sent to the sonar processor on the Jon boat,” Wyness explained.
Within the sonar processor, the time difference between the exiting sonar pulse and the returning one is compared to determine the round-trip travel time a pulse takes to go from the transducer to the lake bottom and back. These pulses can be as frequent as 20 times per second.
The students were also required to perform sound velocity measurements periodically during the hydrographic survey and enter the values into the sonar processor. Sound velocity measurements were collected using a CTD (conductivity/temperature/depth) device as it was lowered from the Jon boat at various project locations and descended to the bottom of the lake. To determine the depth sounding for each pulse — and consequently the lake’s depth in this case — the sonar system multiplies the round-trip travel time of each pulse and the lake water sound velocity and then divides the result by two.
Both the robotic total station and 3D laser scanner employed laser signals to measure angles and distances. The total station, also utilizing Bluetooth radio and Wi-Fi to receive instructions from the operator’s hand-held controller, enabled the students to shoot the elevation of the water surface along the lake’s edge, as well as the banks of the lake. The scanner, incorporating a rotating system that gauged multiple locations in quick succession, generated a set of data points representative of the lake’s physical environment, which included the area of surface algae. Students then estimated the average thickness of the algae at 0.05 feet and 0.1 feet to calculate two scenarios of algae volume.
Honing in on an exact figure was a challenging exercise, says Wyness, because the “algae dissipates very quickly. In the time that we were there … the algae was compacted into one area and then an hour later it was dissipated throughout the lake.”
Overall, the students drove the Jon boat across the lake at roughly 50-foot intervals until the area was fully covered. They calculated the volume of water in the section of the lake that was surveyed to be approximately 132,760 cubic yards, and the volume of algae in the same section to be approximately 660 cubic yards, based on an average thickness of 0.05 feet. A formal presentation to present the findings to the Essex County Parks Department is being scheduled.
Student Viewpoint
SET junior Nick Fetzer participated in the Branch Brook Park project, assisting in establishing horizontal and vertical control (the framework for mapping) around the lake within the project limits, and laser scanning the lake’s outer rim to survey the perimeter, upland topography and extent of the surface algae. He also was involved in obtaining the sonar measurements by setting up and operating the necessary hardware, and processing the field-collected data that, with AutoCAD Civil 3D and HYPACK® software, was used to produce the bathymetric and topographic survey map of the lake’s bottom and the adjacent upland area.
Fetzer has been working in the surveying industry for the past 20 years in a variety of capacities and rose through the ranks to now manage his company’s laser-scanning services. He returned to college for NJIT’s SET program in 2018 and looks forward to receiving his bachelor’s degree, which will allow him to take the New Jersey Professional Surveyors License exam.
“This project was a great introduction to the hydrographic side of surveying. … Communication between the professor and other students proved to be imperative in merging the various data collected from the different hardware platforms,” Fetzer said. “I think our final deliverable was something to be proud of and I look forward to the opportunity of utilizing the knowledge I gained in marine surveying.”
Surveying Engineering Technology (SET) at NJIT is the only four-year program in New Jersey accredited by the Accreditation Board for Engineering and Technology, and serves students from throughout the Garden State as well as New York City boroughs and Eastern Pennsylvania. SET provides four modes of instructional delivery — traditional, online, hybrid and converged — and partners with a range of companies in the industry.
