| With the rapid development of high-speed railway in recent years, the surveying and designing tasks for high-speed railway projects are very heavy and generally suffering from limited construction period. In addition, because most of the railway projects undertaken by the Railway Eryuan Engineering Group (REG) are located in the southwest mountainous areas, it is very difficult and inefficient to perform field measurement. In order to meet the industrial needs, the REG performed an investigation on IMU/DGPS assisted aerial triangulation, As a result, the investigation provided the opportunity and research backbone for this study.Three types of Aerial traditional available in the past couple decades, traditional aerial triangulation, GPS assisted aerial triangulation and IMU/DGPS assisted aerial triangulation. Traditional aerial triangulation requires a large number of external control points to reversely calculate the exterior orientation. Widely used by railway surveying. Although this method demands numerous field works, it’s the most commonly used method. GPS assisted aerial triangulation technology has been applied and tested since the1990s, but it’s not widely accepted in projects due to GPS’s lock failure under high dynamic caused by low sampling frequencies. In recent years, the IMU/DGPS system has been gaining more acceptance among engineers and businesses.This study reviewed the technical principles, theories and methods of IMU/DGPS assisted aerial triangulation. The study summarized the advantages and technical characteristics of IMU/DGPS system as well as described the errors sources and corresponding solutions in IMU/DGPS assisted aerial photogrammetry. It also focused on the role and design principle of GPS base station and calibration site used in IMU/DGPS assisted photography.This study worked closely with REG’s projects on IMU/DGPS assisted aerial photogrammetry missions in the construction of Yunnan-Guilin railway and Sichuan-Tibet railway projects. Many experiments related to the operation procedure, such as GPS baseline solution, GPS and IMU data combined adjustment, calibration of systematic errors by using the calibration site, the standard of refinement, assisted aerial triangulation and orientation mapping bad conducted to evaluate IMU/DGPS assisted aerial triangulation performance. As part of the study, a set of technical processes of IMU/DGPS assisted aerial triangulation been summarized to show suitable for railway surveying.In addition, taking a variety of terrain conditions of the Yunnan-Guilin railway and Sichuan-Tibet railway projects into account, this study designs a complete experiment. To validate the accuracy of the IMU/DGPS, the experiment was adducted at a restricted location and tested multiple times to avoid unreliable biased results. The result demonstrated that by using the IMU/DGPS assisted aerial triangulation, namely:accuracy requirements for large-scale railway mapping can be significantly improved1:10000scale mapping accuracy requirements without control points, and1:2000scale mapping accuracy requirements for four corners with control points.Finally, difficulties during the study and prospect study recommendations for IMU/DGPS lore described. The prospect application of IMU/DGPS assisted aerial triangulation for the construction of railway was anticipated. |
