The performance of an ultra-short baseline (USBL) positioning system is limited by noises and errors from physical environment and other sources. One of the major errors in USBL positioning is to neglect the sensor misalignment which produces static yaw, pitch, and roll offsets. In this study, a circular survey observation scheme is first proposed to study the positioning errors of a USBL system with a fixed seabed transponder. The center of the circular survey scheme is assumed to be located over the top of the transponder. Mathematical equations of the transponder positioning with yaw, pitch, and roll offsets are derived, respectively. According to characteristics of positioning errors arose from yaw, pitch, and roll offsets, an iterative procedure of first getting roll offset, next computing yaw offset, and then obtaining pitch offset for sensor misalignment correction is established. Simulation results indicate that the iterative procedure can effectively obtain all offsets with high determination accuracy and the computation can rapidly converge to desired error tolerance in a few iterations. However, the center of circular vessel survey scheme is almost impossible to be exactly located over the top of the transponder. In such a case, the horizontal positioning error resulting from pitch offset or roll offset is no more a circle function. As a result, it will fail to evaluate the angle offsets through above iterative procedure unless the deviation from real and estimate horizontal transponder position is extremely small comparing to the transponder depth. Therefore, in addition to circular survey scheme, this study proposed a straight survey scheme to study the patterns of positioning error resulting from yaw, pitch, and roll offsets. Similar to the philosophy of establishing the iterative procedure described above, the iterative procedure of first getting pitch offset, next computing roll offset, and then obtaining yaw offset for sensor misalignment correction is established. Again, simulation results show that the iterative procedure can find all offsets with high determination accuracy and has the advantage of quick converging. Besides, the iterative procedure can still obtain correct angle offsets even though there is a constant heading deviation from the direction of the straight vessel track during vessel survey.

Global Navigation Satellite System (GNSS) är ett system för global satellitpositionering och navigering och innefattar bland annat Global Positioning System (GPS) och Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS), dessa två system är de enda fullt globala operativa systemen i dagsläget. Galileo är ett europeiskt satellitsystem under utveckling och erbjuder för närvarande 14 satelliter, men ska bestå av totalt 30 satelliter när systemet beräknas vara fullt fungerande 2020. Den mätmetod med GNSS som har lägst osäkerhet är statisk mätning. Det är en relativ metod vilket innebär att minst två mottagare samlar observationer samtidigt, vanligtvis i flera timmar. Snabb statisk mätning är en vidareutveckling av statisk mätning och erbjuder mycket kortare observationstider, däremot innebär det en begränsning på baslinjelängden. Syftet med denna studie var att undersöka Galileos påverkan vid snabb statisk mätning och se huruvida Galileo kan bidra med lägre osäkerheter, avvikelser och observationstider i olika konstellationer tillsammans med GPS och GLONASS. Mätningarna utfördes under två dagar i fyra respektive två timmar. Två baslinjer mättes; ena baslinjen hade en längd på 0,4 km och den andra på drygt 2 km. I ett bearbetningsprogram delades därefter konstellationerna upp i tio tidsfönster (epoker) och varje tidsfönster delades i sin tur upp i tre sessioner (1, 5 och 10 minuter). Fyra typer av konstellationer testades: GPS, GPS och GLONASS, GPS och Galileo och sist alla tre tillsammans. Resultatet i studien visar på låga osäkerheter när fler än en konstellation används. Lägst osäkerhet uppnås generellt när mätning med alla konstellationer görs. Mätning med endast GPS ger högst osäkerhet i samtliga fall, men detta är framförallt kännbart vid den kortaste sessionen (1 minut). Likheten i osäkerheterna vid den korta och långa baslinjen är tydlig, men osäkerheterna är större för den långa baslinjen. Avvikelserna är lägst med alla konstellationer, men baslinjelängden är i nästan alla fall för kort mot sin referens. Slutsatsen från studien är att Galileo kan användas för att minska observationstider och osäkerheter vid snabb statisk mätning. Detta är dock försumbart ifall GPS och GLONASS redan används, åtminstone för de två baslinjerna i detta test. Låga osäkerheter uppnås antingen med multi-konstellation eller längre observationstider. / Global Navigation Satellite System (GNSS) is a global system for satellite positioning and navigation and consists, amongst other, of Global Positioning System (GPS) and Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS). Currently, these systems are the only fully global operative satellite systems for positioning. Galileo is an upcoming satellite system and offers at the present time 14 active satellites, but will consist of 30 satellites once it is fully operational by 2020. The survey method with GNSS that has lowest uncertainties is static survey. It is a relative method which means that a minimum of two receivers observe simultaneously, usually for several hours. Rapid static surveying is a further development of static surveying and offers much shorter observation times, but it imposes a restriction of the baseline length. The purpose of this study is to evaluate Galileo’s contribution on rapid static surveying and see whether Galileo can decrease uncertainties, deviations and observation times in different constellations with GPS and GLONASS. Measurements were conducted during two days for two and four hours respectively. Two baselines were measured; the first baseline had a length of 0.4 km and the second nearly 2 km. Later in a software, each constellation was divided in ten time windows (epochs) and each time window was then divided in three sessions (1, 5 and 10 minutes). Four types of constellations were tried: GPS, GPS and GLONASS, GPS and Galileo and lastly all three combined. Results show that low uncertainties are obtained when more than one constellation is used. Lowest uncertainties can be obtained with all constellations active. Surveying with only GPS gives the highest uncertainties in all cases, but this is especially true for the shortest session (1 minute). Similarities in uncertainties between the short and long baseline is clear, but uncertainties are higher for the long baseline. Deviations are lower with all constellations active, but the baseline length is in almost all cases too short. The conclusion from the study is that Galileo can be used to lower observation time and uncertainties. However this is negligible when used with GPS and GLONASS, at least for the two baselines in this test. Low uncertainties can be achieved with multi constellation or longer observation time.