# The First Result of Relative Positioning and Velocity Estimation Based on CAPS
## 4 Conclusions  
CAPS is the new navigation concept proposed by the Chinese Academy of Science for establishing a navigation system based on communication satellites. It is currently regarded as an experimental verification platform supporting the design, construction and update of BDS. Based on the real data collected in Beijing, this contribution analyzed the noise of code and carrier-phase measurements and showed the first results of relative CAPS positioning and velocity estimation in post-processing and real-time experiments. The following conclusions can be draw from our numerical experiment.  
1. The noise of the code and carrier-phase measurement from CAPS is about 0.25 m and 0.13 cm, respectively.
2. The accuracies of static relative CAPS positioning based on the code measurement is about 1.26 and 1.80 m in the horizontal and vertical components, while they can be improved to 2.83 and 3.15 cm when using the carrier phase via the ambiguity fixed by the geometry-free approach. The velocity estimation with doppler measurements of CAPS has an accuracy of about 0.04 m/s in the static experiment.
3. The accuracy of kinematic relative CAPS positioning based on the carrier-phase is about 5.21 and 10.41 cm in the horizontal and vertical components, and the accuracy of the velocity estimation is about 0.11 m/s.
4. The relative positioning results in the real time experiment show a periodic feature which needs further analysis with more experiments.  
Figure 12: The spectral analysis result of the east positioning error in static (**left**) and in dynamic (**right**) modes with FFT.  
Figure 13: The error of the velocity estimation based on CAPS in static (**left**) and kinematic (**right**) modes with a sampling rate of 4 Hz.  
Since CAPS is currently still in the development and test phase, this paper only provides preliminary results on relative CAPS positioning and velocity estimation based on limited data and experiments. It should be noted that the data and experiments in this work are quite insufficient to fully represent the performance of CAPS. This is because some of the satellites used in CAPS were rented on a short-term basis, and additionally the ground control station is still being tested. Moreover, the continuous and stabilized service is not available yet, so the available data is limited. With the further improvement of the CAPS system, the collection of longer data and various experiments will expand throughout China in the near future. In addition, we will also compare the positioning result between CAPS and current GNSSs like BDS, GPS, etc.  
[PERSON] proposed the research topic. [PERSON] developed the algorithms and the software, conceived and performed the experiments, analyzed the data and wrote the paper; and [PERSON] developed the CAPS receiver for collecting the data. [PERSON] helped to test the software. [PERSON], [PERSON], [PERSON] and [PERSON] helped to improve the manuscript. All components of this work were carried out under the supervision of [PERSON] and [PERSON].  
This research was funded by the National Key Research Program of China \"Collaborative Precision Positioning Project\" [2016 YFB0501900], the China Natural Science Funds [41674043, 41704038, 41730109], the Beijing Nova program [xx2017042], the Beijing Youth Talent Support program [2017000021223 ZK13] and Beijing Natural Science Foundation [8184092].  
The authors declare no conflict of interest.