What Does This Mean To The United States?
Part 2

Satellite signals can be improved for special aviation applications, such as landing planes during poor visibility. GPS is continually being improved and modernized. It is easy to see that the aviation industry, particularly the airlines, badly needs GPS. With so many airplanes in the air it becomes increasingly important to know where they are.

GPS has greatly affected marine operations, including search and rescue. GPS provides the fastest and most accurate method for mariners to navigate, measure speed, and determine location. This increases levels of safety and efficiency for mariners worldwide.

It is extremely important in marine navigation to know your vessel's exact position while in the open sea, or congested harbors. The need for accurate position information becomes even more critical as a vessel departs from or arrives in port. GPS is also used for underwater surveying, buoy placement, and navigation in a hazard location. Commercial fishing fleets use GPS to navigate to optimum fishing locations, and to ensure compliance with regulations. Maritime operations also enjoy higher precision and increased safety using Differential GPS. ( DGPS ). And now we come to perhaps the most important weapon in our arsenal, the submarine. It is an absolute necessity for the sub to always know its exact position.
Later we will see that the Tomahawk missiles fired by our subs are dependent on GPS to guide them to their target.

A typical engineering company accomplishes ground-based surveying with geodetic-grade ( centimeter accuracy ) GPS receivers operated in static or kinematic mode, depending on project requirements. Trimble mapping-grade receivers are used for sub-meter accuracy survey work. Also used in surveying are automatic levels, total station, and theodolites. Horizontal control can be surveyed to 1st or 2nd order accuracy using GPS, while vertical accuracy with GPS can be surveyed to 2nd order accuracy with precise leveling. Ground surveying using GPS is used in mapping of highways, railroads, dams, lakes and rivers, airports, transmission lines, plant sites, landfills, hazardous waste sites, and wetlands to name a few. A large percentage of surveying work is done utilizing aerial photogrammetry. This requires very expensive equipment, such as modified aircraft, first order aerial cameras, complete photo lab, rectification systems, and highly qualified personnel. Primary photogrammetric-grade image acquisition systems require the latest generation USGS-calibrated aerial cameras, such as the Zeiss RMK TOP 15 with built-in forward motion compensation producing resolution in the highest range. This camera can be operated using automatic gyrostabilizing mounts which are linked to geodetic-grade APPLANIX 510 POS/AV airborne GPS/IMU systems which record the exact camera position and spatial orientation at the instant of each exposure. This produces automated image geo-referencing accurate within inches. The transition of the captured photo image to the final product requires sophisticated instrumentation operated by well skilled photogrammetrist. Aerial surveying has progressed at an unbelievable rate in recent years, and is now an important part of aerial and ground surveying.

Without exaggeration our military would be greatly affected if they did not have GPS. In the Korean war it was common to send 10 B-29s with 500 pound bombs to destroy a bridge. Many times after bomb damage assessment ( BDA ) photos showed the bridge to be undamaged and another flight was scheduled. It was common for a perfect bomb run to have its bombs "straddle" the bridge. That is where GPS comes in. With precision guided weapons the bridge could conceivably be destroyed by one well placed bomb. The U.S. has experimented with Radio-controlled weapons, laser guided weapons, Radar/infrared/electro-optical, only to arrive at the conclusion that GPS offered the most accurate delivery system. In some instances TV guided bombs are still being used. The laser had a disadvantage of not being useable in poor weather. The problem of poor visibility has no effect on satellite guided weapons. At present it is still possible to jam GPS. Several companies are developing advanced guidance concepts, combining laser guidance to the GPS guided system.

Possibly our most important weapon is the all-weather submarine or ship launched land-attack cruise missile. Our BGM-109 Tomahawk is such a weapon. It is highly survivable, difficult to detect because of its small cross section, and its low altitude flight. Infrared detection is difficult because the turbofan engine emits little heat. The land attack version of Tomahawk has inertial and terrain contour matching guidance.


The Tomahawk is a long -range, highly survivable, land attack weapon system capable of pinpoint accuracy. It offers the Navy a deep strike capability. Submarines utilize a different weapon control system to guide the Tomahawk. On the attack submarines, missiles are fired from torpedo tubes. Some of our subs have a vertical launch system located forward, external to the pressure hull, which will handle both storage and launch. Since the Gulf War, the Tomahawk has an increased target penetration, along with better range and accuracy. The GPS guidance control utilizes a jam proof missile. Inventory of Tomahawk missiles is underway with over 4,000 missiles currently in stock. The Tomahawk is built by Hughes Missile System Co. It uses a turbo fan engine which has a solid fuel booster. Weighing 2650 pounds, it has a range of 690 miles at a speed of 550 mph. The Tomahawk production model cost $500,000.


By Wayland M. Mayo
Wayland is a Professional Surveyor and Mapper (ret) In the state of Florida.
Chief Photogrammetrist, pilot,(ret) Korea Veteran RB-29 "Tiger Lil."

Sources: U.S. Coast Guard, nav. Center GPS
Library of congress
Associated press
U.S. Department of Defense
U.S. Navy

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