NAVACE is a revolutionary navigation system under development by Electrospace Systems, Inc. NAVACE utilizes a concept of ocean bottom and sub-bottom feature correlation to determine accurate ship positioning within a surveyed ocean area. Accuracies of 0.05% within a 30 × 30 mile operating grid are well within NAVACE's capability. NAVACE is adaptable to surface ship, submersible or tethered vehicle navigation.
NAVACE provides an operational advantage of eliminating deployment of reference pingers and transponders to obtain precision positioning data during offshore operations in surveyed areas. Since reference grids utilized for correlation represent essentially permanent geophysical characteristics, renavigation becomes as simple as initial area navigation with NAVACE.
This paper summarizes the design, discusses accuracies and presents equipment status.
Since man first became interested in utilizing the oceans to support transportation, accurate navigation has been a challenge. Early sailors utilized geophysical references for navigation. The characteristics of a shoreline, an island formation, a man-made tower or a far-off mountain peak became key reference marks along his path of travel. Then, as technology progressed, the magnetic compass and celestial navigation techniques were developed and applied. The twentieth century became the era of even more significant advances in ocean navigation. Electronic technology brought about navigation utilizing radio, radar and sonar ranging. Inertial navigation was perfected. Computers were applied to provide more precise position reference timing measurements and resulting positioning fix calculations.
The era of satellites brought about a new dimension in ocean navigation. By appropriately calibrating satellite position relative to earth coordinates, ships can communicate with satellites to determine their coordinates. Tomorrow promises mariners twenty-four hour, full earth coverage by navigation satellites to provide ocean navigation capability on a continual basis.
Offshore navigation requirements vary with application. Requirements can be classified in several ways. The two common classifications are Enroute and Terminal Navigation. Utilizing Air Traffic Control as an example, enroute implies less accuracy and less precise control while terminal implies precise accuracy and precise control.
A class of navigation equipments has been developed which supports terminal navigation. These range from TOA-DF type radio ranging to their sonar equivalents. Most of these equipments operate within a limited range of transponders or emitters. Obviously sonar is much more limited than radio. These systems are currently the backbone of offshore, terminal area operations.
Terminal area operations, as referenced in this paper to the offshore industry, refer to work areas. Work area relates to survey, drilling, inspection, mining, platform construction, etc. The work task not only involves a specific ocean area as defined in the work contract, but also involves specific geophysics within the area.
Enroute navigation, as described, implies navigation tasks of getting the ship to the work area to perform contract requirements. Enroute navigation may involve LORAN, OMEGA, Inertial, SATNAV, DOPPLER, etc. Usually the terminal area work task involves navigation accuracies exceeding those of enroute navigation equipment by several orders of magnitude.
