Small-sized unmanned aerial vehicles (UAVs) have been widely investigated for use in a variety of applications such as remote sensing and aerial surveying. Direct three-dimensional (3D) mapping using a small-sized UAV equipped with a laser scanner is required for numerous remote sensing applications. In direct 3D mapping, the precise information about the position and attitude of the UAV is necessary for constructing 3D maps. In this study, we propose a novel and robust technique for estimating the position and attitude of small-sized UAVs by employing multiple low-cost and light-weight global navigation satellite system (GNSS) antennas/receivers. Using the "redundancy" of multiple GNSS receivers, we enhance the performance of real-time kinematic (RTK)-GNSS by employing single-frequency GNSS receivers. This method consists of two approaches: hybrid GNSS fix solutions and consistency examination of the GNSS signal strength. The fix rate of RTK-GNSS using single-frequency GNSS receivers can be highly enhanced to combine multiple RTK-GNSS to fix solutions in the multiple antennas. In addition, positioning accuracy and fix rate can be further enhanced to detect multipath signals by using multiple GNSS antennas. In this study, we developed a prototype UAV that is equipped with six GNSS antennas/receivers. From the static test results, we conclude that the proposed technique can enhance the accuracy of the position and attitude estimation in multipath environments. From the flight test, the proposed system could generate a 3D map with an accuracy of 5 cm.

翻译：小型无人机在遥感及航空测绘等众多应用领域已得到广泛研究。针对小型无人机搭载激光扫描仪的直接三维地图构建是众多遥感应用的需求。在直接三维地图构建过程中，获取无人机精确的位置与姿态信息是实现三维地图构建的关键前提。本研究提出一种新颖且鲁棒的技术，通过采用多个低成本、轻量化的全球导航卫星系统天线/接收机，实现小型无人机位置与姿态的高精度估计。利用多GNSS接收机的"冗余"特性，我们采用单频GNSS接收机增强了实时动态差分定位的性能。该方法包含两个核心策略：混合GNSS固定解算方案与GNSS信号强度一致性校验。通过融合多天线间的多路RTK-GNSS固定解算结果，可显著提升单频GNSS接收机下RTK-GNSS的固定率。此外，采用多GNSS天线可进一步通过多径信号检测技术提升定位精度与固定率。本研究开发了配备六组GNSS天线/接收机的原型无人机系统。静态试验结果表明，所提技术在多径环境下可有效提升位置与姿态估计精度。飞行试验显示，该系统能够生成精度达5厘米的三维地图。