Processing Of Data From A New Radio Ranging System (1978)

ABSTRACT Until recently, precise offshore radio positioning beyond line of sight typically involved the ambiguous measurement of two ranges or two range differences, and careful monitoring of lane crossings through the use of a strip chart recorder to detect and correct lane errors. However, operation at increasing distances from shore results in an increasing probability of uncorrected lane count errors due to sky waves, interference or atmospheric disturbances. A recently introduced Radio Ranging system can measure up to four independent ranges and also provides data which is indicative of the quality of the ranging signals. This increased information from the radio positioning system creates an opportunity to employ advanced automatic data processing to reliably detect and correct lane count errors. This paper presents the results of recent efforts by Cubic Western Data to optimally process range data using Kalman filter techniques to establish the most probable position and most probable lane count errors under adverse ranging conditions. The method of processing is described and the results of field tests are presented. The results indicate the potential for more reliable accurate long-range positioning for surveys and construction while reducing down time and the need for backup positioning systems and techniques to confirm lane counts. DESCRIPTION OF THE RADIO RANGING SYSTEM The described data processing techniques are designed for the ARGO Model DM-54 Radio Ranging System. This Ranging system experienced its first operational usage in March 1977 and since then has been used in survey and search applications in many areas including the Gulf of Mexico, the coastal waters of California, New Jersey, Labrador, Norway, Venezuela and Southeast Asia. Fig. 1 shows the major equipments of the system which consist of the Range Processing Unit (RPU) and the Control Display Unit (CDU). The Range Processing Unit, when connected to an antenna system, serves the function of a shore or reference station. The Control Display Unit, when connected to the RPU, permits the combination to function as a mobile station. The mobile station can measure over the horizon distances to a maximum of four shore stations. Up to seven mobile stations (users) can be serviced by this four shore station net. Alternate system configurations include but are not limited to the following:Six users measuring four ranges plus an unlimited number of users measuring three hyperbolic LOP's.Nine users measuring three ranges.Eight users measuring three ranges plus an unlimited number of users measuring two hyperbolic LOP's.Seven users measuring four ranges utilizing both the two-way and one-way ranging method with the addition of cesium clocks. 41.7 SIGNIFICANT RANGING SYSTEM DATA CHARACTERISTICS The Radio Ranging System provides output data in the form of lanes up to a maximum value of 9999.99 lanes. The lane width is determined by the assigned carrier frequency and is typically on the order of 85 meters. Up to four range words per data sample are provided through either a general purpose interface bus or an optional RS-232 interface.