Inside GNSS Media & Research

SEP-OCT 2018

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64 Inside GNSS S E P T E M B E R / O C T O B E R 2 0 1 8 www.insidegnss.com geodetic pillars. One pillar, in which the multistation was installed, and the remaining two to use as multiple back sights. is step allows for having the coordinates of the targets in a global reference system instead of the instru- ment's local coordinate system. UAV For our UAV, we chose a professional octocopter drone. e octocopter has a weight of 4.9 kg and is able to carry a payload of approximately 6 kg (includ- ing the batteries). The air time fully equipped is 12 minutes. e drone has IMU, GPS, and compass modules on board for stabilization. To shield the UAV electronics (especially the GPS antenna) from RF interference, a n a lu mi nu m g rou nd plate must to be installed between the UAV GPS antenna and at the Tx antenna. It was also nec- essary to cover the housing of the mini PC with EMV paint to ensure the UAV GPS recep- tion. e housing of the mini PC as well as the mounts for the USRP, prism, Tx antenna, and battery were self-designed and 3D printed. A list with the main parts is shown in Table 1 . The labels refer to the corre- sponding parts in Figure 6 . Results Full results and more will be published in Part 2 in the November/December issue of Inside GNSS. Additionally, a full version of the article will be published online at insidegnss.com. Manufacturers The sof t ware def ined radio recon- figurable device used in the Pseudolite (Transmitter) section is a SDR USRP 2950R from National Instruments, Austin, Texas. Also, the virtual bench with a customized application program that was used to measure the time dif- ference between the clocks of the WR- LENs was the VB-8054 from National Instruments. In Receiver System where the authors state that the UAVlite signals as well as the signals in space (SIS) are captured, WORKING PAPERS FIGURE 5 MS60 as a reference system and geometrical description of the measurement's scenario Item Label DJI s1000+ A USRP 2950R B Mini PC (ASRock) + EMV Shielding C 360° Leica Prism D Tx Helix Antenna + Ground plate E WiFi Antenna F UAV GPS + Ground plate G Total Weight 10.800 g Table 1. UAV item list FIGURE 6 Figure caption to their phase center: Rx antenna 1 and Rx antenna 2, which stay on ground and have a static position; and the Tx anten- na, which is mounted on the UAV and is tracked during the flight (see Figure 5 ). Hence, a complete description of the geometry between the three phase cen- ters is possible at all times. is allows the computation of the real distances (ρ 1 , ρ 2 ) between the Rx antennas and the Tx antenna. For Rx antenna 1 and Rx antenna 2, single point measurements are done with the multistation, as they are fixed on the ground and their position is stat- ic. On the contrary, with the Tx antenna, the data measured by the multistation is streamed in real time to PC2 through a Bluetooth connection at 20 hertz. e 20 hertz is the ma ximum measure- ment rate. In our test we observed a mean rate of 15 ± 5 Hz. e streamed data is stamped with the time given by the multistation. e time of PC2 and the multistation is synchronized at the beginning in the range of milliseconds, thus allowing a direct comparison with the signal recorded on PC2 as they share the same timestamp. Among the data that is streamed, one can find: North- ing [m], Easting [m], Elevation [m], hori- zontal angle [rad], vertical angle [rad], slope distance [m], and time stamp [hh:mm:ss.ss]. Another point worth mentioning is the multistation setup, which is per- formed prior to the measurements, in which the computation of the orienta- tion of the instrument is performed by using the known position of three

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