Development and Implementation of an Embedded LowCost GNSS Receiver Emulator for UAV Testing This paper introduces the development and implementation of lowcost navigation satellite system (GNSS) receiver emulator. The main motivation of this work is to facilitate the testing process of autonomous vehicles, which depend on satellitebased navigation. The proposed emulator can generate National Marine Electronics Association (NMEA) code relevant to several messages while targeting GPS or GLONASS systems. The architecture of the proposed emulator is presented along with implementation targeting lowcost electronic components. Testing of the developed version of the emulator demonstrates that it can provide a solution that facilitates testing the interaction between unmanned aerial vehicles (UAVs) and GNSS receivers without actually flying them.

Robust UAV Position and Attitude Estimation using Multiple GNSS Receivers for Laserbased 3D Mapping Smallsized unmanned aerial vehicles (UAVs) have been widely investigated for use in a variety of applications such as remote sensing and aerial surveying. Direct threedimensional (3D) mapping using a smallsized 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 smallsized UAVs by employing multiple lowcost and lightweight global navigation satellite system (GNSS) antennasreceivers. Using the xe2x80x9credundancyxe2x80x99u0027 of multiple GNSS receivers, we enhance the performance of realtime kinematic (RTK)GNSS by employing singlefrequency GNSS receivers. This method consists of two approaches: hybrid GNSS fix solutions and consistency examination of the GNSS signal strength. The fix rate of RTKGNSS using singlefrequency GNSS receivers can be highly enhanced to combine multiple RTKGNSS 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.