Channeling the Oceans
Called one of the greatest engineering achievements the world has known, the Panama Canal officially opened in August of 1914. This transcontinental canal was the most expensive construction project in U.S. history to that time and cost around $375,000,000, including payments for the rights to build. Interesting to many is that it came in under budget by about $23,000,000, in spite of landslides and design changes. Today, the 51-mile canal is undergoing a vast modernization and improvement program to ensure the waterway remains viable and competitive into the next century. And GPS is part of the modernized solution.
The multi-year, $1-billion capital investment program began in 1996; some projects included in the program have been completed and others are still in process. At the project's completion, Canal transit capacity will be increased by about 20 percent, guaranteeing a modern waterway and sufficient capacity for the Canal to meet projected traffic demand safely and efficiently well into the next century.
The Canal modernization program followed a U.S. Army Corp of Engineers review of the Canal's physical plan. Completed in 1996, the yearlong review included a panel of Panamanian engineers who evaluated the Corps' work. Along with normal maintenance concerns, the increased size of ships using the waterway has put added pressure on the Canal. In fact, the Canal has become such a critical passageway for world travel that it birthed a category of ship, the Panamax, which is the largest ship specifically built to fit through the Canal locks. Approximately 13,000 to 14,000 vessels use the Canal every year; and today it is expected that the number of Panamax ships using the Canal will increase from one fourth to more than one third of the total transits by the year 2010.
Because of the vessel size issue, one of the main projects in the Canal's modernization and improvement program included the widening of Gaillard Cut, a mid-section of the channel that allows two wide-beam Panamax ships to move simultaneously in either direction without impairing navigational safety. Following the completion of the Gaillard Cut project in November 2001, work on deepening the Gatun Lake Channel was begun and continues today. Other projects included increasing the towboat fleet, purchasing new and more powerful locks locomotives, modernizing the marine traffic management and locks control systems, and replacing 50,000 feet of locks tow track. Modernization project funding has been generated by increases in toll revenues.
Journey Through the CanalFrom its Atlantic entrance, a trip along the Canal would take you through a seven-mile dredged channel in Limon Bay, then 11.5 miles to the Gatun Locks, the first of the Canal's three sets of locks. Gatun Locks has a series of three locks, with Pedro Miguel consisting of one series of locks and Miraflores two series; each lock set raises and lowers ships from the Atlantic to the Pacific sea-levels, or vice versa. The Gatun lockset raises ships 85 feet to Gatun Lake, one of the largest manmade bodies of water in the world. The journey continues through a channel in Gatun Lake for 32 miles to Gamboa, where the Gaillard Cut (also known as Culebra Cut, the Spanish term for snake because of the waterway's curving form) begins. Eight miles through the Gaillard Cut brings you to the Pedro Miguel locks, which lowers ships 31 feet to a lake. The lake then takes you to the Miraflores Locks, which lowers ships 52.5 feet to sea level at the mouth of the Pacific Ocean in the Bay of Panama.
The lock chambers, called steps, are 110 feet wide by 1,000 feet long. Water from Gatun Lake is used to raise and lower vessels in each set of locks; the water comes into the locks through a system of main culverts extending under the lock chambers from the sidewalls and center wall.
The Canal dramatically reduces time and distance traveling between the Atlantic and Pacific Oceans by eliminating the need to round the base of South America. For example, using the Canal on a trip from New York to San Francisco would save a total of 18,000 miles. That's an average of 8 to 10 hours through the Canal compared to 26 days at 25 knots traveling around South America.
GPS at the CanalThe Panama Canal Authority (the English translation for La Autoridad del Canal de Panamá, or ACP) is the Panama government agency responsible for the Canal. With a work force of approximately 9,000 employees, ACP operates the Canal 24 hours a day, 365 days a year. Its Engineering and Projects Department includes the survey branch, which has been involved in many of the modernization projects. ACP has long used Global Positioning System (GPS) technology, employing it in the modernization projects in a variety of ways.
Initially, ACP worked to densify the Canal's first-order geodetic control network. The network was first established as a support for Panama's rural cadastral project. Surveyors could use the base station files to post-process their data and get sub-meter accuracy for the project. The network densification involved a new and strong tie to the World Geodetic System of 1984 (WGS-84) and the establishment of a geoid model due to increased needs for precise elevations. For this purpose, in 1999, three points in the network boundary were tied to Continuously Operating Reference Stations (CORS) outside of Panama, in the Caribbean, Central America and South America; the entire network was then re-measured for a new adjustment.
For the improvement project, ACP reviewed several manufacturers' GPS receivers and chose Trimble (Sunnyvale, Calif.) equipment. ACP believes the equipment is reliable, offers high accuracy and close tolerances, and is easy to operate and rugged enough to use in a rough environment, critical for the extremely hot and humid Panama climate. ACP used seven Trimble survey grade receivers with compact L1/L2 antennas; the adjustment was done with Trimble GPSurvey software. ACP is also planning to expand the CORS network in the future. The CORS uses Trimble Reference Station Software with a serial link to get the data to the office, approximately 6.3 miles away. All the data is public, 24-hour data files can be downloaded from the ACP Internet site, and coordinates of the rest of the points can be obtained in ACP's office.
All the dredging and earth movement work for the modernization projects have been dependent on the RTK GPS network. The development of research areas in the remote areas of the watershed depended on the geoid model because normal leveling would have been too expensive to complete. In the remote areas, ACP used static observations in smaller network densifications; these were always tied to three or more control stations from the first-order control network.
Gaillard Cut WideningHistorically, the narrowest portion of the Canal is Gaillard Cut, which extends from the north end of Pedro Miguel Locks to the south edge of Gatun Lake at Gamboa. This segment, more than 8.5 miles long, is carved through the rock and shale of the Continental Divide. During its initial construction, this section of the Panama Canal required the largest excavation volume and experienced the largest landslides. Even today landslides disrupt Canal passage through this section.
The widening project increased the Cut's span to at least 0.12 miles of straight stretches and 0.14 miles in the curves. It is estimated that increasing the breadth of Gaillard Cut will increase the lock's potential to accommodate more traffic by more than 90 percent as well as reduce the risk of landslides that could disrupt Canal operations.
For the project, ACP equipped its two dredges with Trimble GPS receivers with TRIMMARK radios. Both the dredges and the drill boat barge received differential corrections from five Trimble RTK GPS base stations located along the Canal. The RTK system allows precise, real-time positioning 24 hours a day, eliminating the problems of positioning the dredges and hydrographic vessels, and improving the confidence of ACP's work. In addition, ACP surveying boats are equipped with Trimble GPS receivers and TRIMMARK radios using the same differential corrections.
The positioning of the dredges for the widening project was critical. GPS allows all the dredging work to be done without interrupting the moving vessels. ACP surveyors produced the hydrographic charts, from which the drill boat prepared a drill pattern and blasted the area to fracture the rock. After the blasting work, ACP surveyors provided additional hydrographic surveys for one of the dredges to dredge up to the design depth.
The last blasting was performed on July 4, 2001, thus ending the drilling and blasting portion, while on August 16 the R994 hydraulic excavator from Liebherr-Werk Ehingen GmbH (Liebherr-International AG, Bulle, Switzerland) lifted the last shovelful of the wet excavation work from land. A grand total of 23.2 million cubic meters of dry material and 12 million cubic meters of underwater material were removed. The major widening work ended in November 2001, when one of the dredges removed the last portion of rock and shale from Gaillard Cut.
Aids to NavigationACP also uses GPS to help vessels navigate through the Canal. Each pilot (captain) carries a small GPS receiver and transmitter with a laptop. Though it's not used for general navigation purposes, the GPS helps the pilot traverse safely through the Canal. This system, called CTAN-AIS, AIS for Automatic Identification System, is part of the modernization of the marine traffic management; its main use is for safety and administrative purposes.
The CTAN-AIS system uses two radio beacon stations that broadcast differential corrections-one on the Pacific and the other on the Atlantic side. The Atlantic radio beacon is powerful enough to cover the whole country. Each base station includes a Trimble 4000 reference station with a Trimble 4000 Integrity Monitor system using a Nautel transmitter (Hackett's Cove, Nova Scotia, Canada). Radio beacons and GPS receivers are maintained by ACP's Department of Information and Technology.
The CTAN-AIS system is part of the Enhanced Vessel Traffic Management System (EVTMS) that is expected to put the Panama Canal at the forefront of the world's maritime traffic administration. CTAN-AIS sends the vessels' location information via radio to a central computer at the Maritime Traffic Control Center. At the center, all Canal vessels, launches and towboat information are integrated; the information is sent to each pilot, who is able to visually see and monitor all transiting vessels and Canal support equipment. Pilots can check for the vessel's speed, distance to the banks, to other vessels, or to the locks. In addition, pilots can easily find out the time and meeting point with other vessels. This information is also available to Maritime Traffic Control Center controllers, as well as officials from different support units.
Finally, ACP is also repairing the Tow Tracks, along which locomotives tow the vessels through parts of the Canal. The Canal tow track system includes three track types: towing tracks, return tracks and spur tracks. The return tracks, which allow locomotives to circle the chambers, are currently in use only at the Gatun Locks. ACP surveyors provided topographic surveys using Trimble GPS and conventional total stations for the alignment, positioning and leveling for replacing all tracks.