TDOA measurement capability, and one with TDOA measurement capability). For simplicity these three methods are referred to as AOA, TDOA, and hybrid AOA/TDOA. Note that a monitoring site capable of AOA measurement is called an AOA site; a monitoring site capable of TDOA measurement is called a TDOA site, and a monitoring site capable of both AOA and TDOA measurements is called a hybrid AOA/TDOA site. The main characteristics of the three geolocation methods are listed in the Table 1 below. (See Report for a more detailed discussion of the advantages and limitations of TDOA systems.) 1 Geolocation System Hybrid AOA ONLY TDOA ONLY Characteristics AOA/TDOA 2 Stations, hybrid Minimum number AOA/TDOA. of sites required 2 Stations 3 Stations One station can be for geolocation TDOA only Approximately constant Same as TDOA in between in the area between Linear decreasing the TDOA sites the hybrid sites as the distance to Geolocation Accuracy monitoring station Deteriorate rapidly Similar to AOA increases in the area outside in the area outside the TDOA sites the sites Accuracy decreases Only for transmitters Only for transmitters with increasing Yes in the area outside located far away from distance to emitter the TDOA sites the hybrid TDOA does not work against unmodulated Independent of signal Yes, if there are at least signals Yes modulation two hybrid sites Difficult for narrowband signals Can be as low as AOA, if only AOA is used or Data communication Medium to High, slightly higher than Low, 10-30 kbit/s requirement 120 kbit/s 2 Mbit/s TDOA, if AOA and – TDOA are simultaneously used 1 (end) Larger antenna may be Siting constraints Simple Omni, Same as AOA for harder to erect, possibly (See § 3) easier to erect hybrid sites limiting site availability Multi-element and/or Antenna complexity Multi-element antenna Single antenna Single-element antenna Calibration Sometimes (depends on Sometimes (depends No requirements AOA system) on AOA system) As the Table shows, there are a number of advantages and disadvantages to each method. In a specific application, (urban/suburban, permanent/temporary, flat terrain/mountainous, etc.), the requirements for the deployment will determine the optimum configuration.
TDOA measurement capability, and one with TDOA measurement capability). For simplicity these three methods are referred to as AOA, TDOA, and hybrid AOA/TDOA. Note that a monitoring site capable of AOA measurement is called an AOA site; a monitoring site capable of TDOA measurement is called a TDOA site, and a monitoring site capable of both AOA and TDOA measurements is called a hybrid AOA/TDOA site. The main characteristics of the three geolocation methods are listed in the Table 1 below. (See Report for a more detailed discussion of the advantages and limitations of TDOA systems.) 1 Geolocation System Characteristics AOA ONLY TDOA ONLY Hybrid AOA/TDOA Minimum number of sites required for geolocation 2 Stations 3 Stations 2 Stations, hybrid AOA/TDOA. One station can be TDOA only Geolocation Accuracy Linear decreasing as the distance to monitoring station increases Approximately constant in between the TDOA sites Deteriorate rapidly in the area outside the TDOA sites Same as TDOA in the area between the hybrid sites Similar to AOA in the area outside the sites Accuracy decreases with increasing distance to emitter Yes Only for transmitters in the area outside the TDOA sites Only for transmitters located far away from the hybrid Independent of signal modulation Yes TDOA does not work against unmodulated signals Difficult for narrowband signals Yes, if there are at least two hybrid sites Data communication requirement Low, 10-30 kbit/s Medium to High, 120 kbit/s – 2 Mbit/s Can be as low as AOA, if only AOA is used or slightly higher than TDOA, if AOA and TDOA are simultaneously used 1 (end) Siting constraints (See § 3) Larger antenna may be harder to erect, possibly limiting site availability Simple Omni, easier to erect Same as AOA for hybrid sites Antenna complexity Multi-element antenna Single antenna Multi-element and/or Single-element antenna Calibration requirements Sometimes (depends on AOA system) No Sometimes (depends on AOA system) As the Table shows, there are a number of advantages and disadvantages to each method. In a specific application, (urban/suburban, permanent/temporary, flat terrain/mountainous, etc.), the requirements for the deployment will determine the optimum configuration.
R-REP-SM.2211-1-2014-MSW-E.docx