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Aiming to Please

By Ken Greene

The M-3000 Electronic Luminaire Aimer is accurate to within one-half of one degree and reads magnetic north 10 times a second.

Positioned 52 feet above the roadway on 43 towers at the NY/NJ Port Authority George Washington Bridge toll plaza are nearly 200 floodlights. To maintain safe access at night on the converging roads at the toll plaza for the millions of passengers and the vehicles that cross the bridge each year, the Authority uses floodlights that illuminate more than 3,500 feet of roads leading to the bridge's toll plazas.

Magniflood, Inc., of North Amityville, NY was challenged to retrofit outdated toll plaza luminaries with floodlights that would be more efficient, use lower wattage and be easier to maintain. They were asked, as well, to devise solutions to meet four critical requirements:

In addition to the above, the lighting fixtures needed to have narrow beam patterns to minimize glare and light pollution. Precision accuracy of the aiming method was equally important to the Authority. The task of aiming these floodlights easily, accurately, and quickly-while a significant challenge-was an extraordinary opportunity for the company to illustrate its technical expertise, design and manufacturing capabilities.

Conventional methods previously used to aim floodlights required the area to be surveyed to define and locate the aiming coordinates of each luminaire. These coordinates were established from an origin and plotted to pinpoint the "X-Y" coordinate locations on the ground. This particular method required the contractor to have personnel up in a bucket truck with a sighting device to attach and correctly position the luminaires. The luminaires would then be aimed to specific "X-Y" coordinates. Slow, tedious and necessitating the closing of lanes of traffic for extended periods, the accuracy of this type of aiming over such a large area was questionable, at best.

For lighting design engineers to produce precision lighting layouts, the computer age has placed the power, speed and accuracy of mathematical calculations in their hands. Software enables the importation of complex AutoCAD drawings or the creation of original layouts. This, in turn, permits the placing of fixtures and poles onto the drawing to develop a point-by-point lighting calculation. Engineers needed-and found-a way to accurately translate the data from the computer to a precisely lit roadway.

The New York/New Jersey George Washington Bridge toll plaza lights illuminate more than 3,500 feet of roads leading to the toll plaza.

Computer layouts generate a schedule of fixture locations in "X-Y-Z" coordinates. These aiming coordinates also defined "orientation angles" (luminaries rotated on their vertical axes to a given point in the horizontal plane) and "tilt angles." (luminaires tilted in the vertical plane from nadir toward the horizon to a given point"). Utilizing lighting software, engineers established that 150 400-watt high pressure sodium floodlights would achieve the light levels being sought by the Authority.

The company provided its client with a computer-generated layout of the roadway. Using a CAD drawing provided by the Authority, lighting engineers were able to position and aim 150 floodlights to orchestrate a precision layout in the computer. This data was then used to address the field aiming of the floodlights. To further reduce installation time and contractor costs, each fixture was aimed at the time of installation and without being energized, thus keeping lane closures to a minimum.

Focusing the floodlights so they matched the computer-designed layout is an arduous task. Engineers devised an accurate, reliable, portable and, most of all, foolproof method for a contractor to use in the field. The Port Authority survey gave tower locations and defined a "true north" direction. It also gave the company the opportunity to import the drawing into the lighting software to perform the lighting layout calculations. This minimized error and helped to ensure accuracy. For such a large area, a reference point was needed that could be depended upon to remain fixed and constant over the two-thirds of a mile of roadways. A Global Positioning System (GPS) was considered, but it was decided instead to employ space age electronics that senses and reads the earth's magnetic field.

A sophisticated magnetic electronic sensor combined with a simple angle locator solved the problem. The magnetic sensor would provide the orientation angle and the angle locator would provide the tilt angle.

To ensure accuracy, the sensor could be calibrated in the field with the use of a laptop computer. It is accurate to within one-half of one degree and reads magnetic north 10 times a second. With a 12 volt rechargeable battery system, the Aimer is totally portable. It has a three-inch digital screen with large numbers and the unit is encased in a heavy-duty cast aluminum housing. The slip-on mounting bracket allows the sensor to be attached to each floodlight in a matter of seconds; the glass lens of the floodlight serves as the reference surface to position the device.

Before field tests were performed, several more details were addressed. The orientation angles generated by the lighting software defined 0 degrees on the positive side of the X axis at 3 o'clock. A compass defines 0 degrees at 12 o'clock-a 90-degree difference. Additionally, the bridge location has a 13-degree magnetic deviation between true north and magnetic north. These two factors had to be figured into an equation that would allow the computer data to be translated into field-usable data for the contractor. Engineers interpolated the computer layout data by using the following equation: [360 degrees] – [orientation angle] + [90 degrees] + [35 degrees] = magnetic aiming orientation angle. (The 90 degrees is the difference between the 0 angle for X-Y coordinates and the 0 degree of a compass rose. The 35 degrees is the addition of the deviation angle, 13 degrees, plus the angle to true north, 22 degrees, on the survey drawing with respect to its X-Y axis.)

The development of a tool-less floodlight to reduce future maintenance costs was the last of the requested considerations. The company had previously developed a tool-less luminaire for the Authority, the VERTILITE-3, for lighting the lower level of the George Washington Bridge. These fixtures have been in service for several years and the tool-less features have proven to reduce maintenance costs and lane closure time. Modifications incorporating hinges, latches and quick disconnects were made to our existing floodlight design. This would enable a maintenance electrician with gloved hands and no tools to remove and replace lamps and ballasts while the fixtures remained aimed in the correct positions. A prototype floodlight was submitted to the facility for evaluation and ultimate approval.

To facilitate installation, the company placed the fixture aiming data, tower number and fixture number on two permanent weather-resistant labels-one inside the luminaire and visible through the lens; the other on the exterior of the luminaire. This would give the Authority the ability to track each fixture for maintenance and at the same time let the installing contractor use the information to aim each floodlight.

The company called the new focusing device the MF-3000 Electronic Luminaire Aimer (patent pending), and now proudly introduces it to the marketplace. The simplicity of this technologically advanced system with its large and portable digital read-out, made aiming nearly 200 luminaires fast, easy and economical and placed precision aiming directly in the hands of electrical design engineers and contractors.

  1. Provide a computer-generated layout of the entire 3,500 feet of roadway utilizing the existing towers.

  2. Enable precision aiming of fixtures during installation with minimal traffic flow interruption.

  3. Use a more efficient and lower wattage fixture than the ones being replaced.

  4. Develop a tool-less fixture to reduce maintenance costs.

This product recently took “Best in Category” at LightFair International’s New Product Showcase.

Ken Greene, R & D engineer, is president of Magniflood, Inc.

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June 18, 2019, 9:07 pm PDT

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