# Cloud-Based Single-Frequency Snapshot RTK Positioning
## 4 Conclusions  
The results presented in this paper show how SRTK is able to achieve IAR and obtain a high accuracy solution with long baselines of up to 50 km, confirming for the first time that the SRTK technique can be practically functional in real scenarios, i.e., non-zero baselines. The manuscript explored the influences of signal bandwidth, integration time and baseline distance, and for this purpose, the collected snapshot data set was processed using different combinations of settings. The results show that higher bandwidths and longer integration times lead to better performances of the SRTK engine in terms of RTK fix rate and mean LRF value for all the snapshots, although at the price of a larger size of data to be transmitted and a higher computational burden. These two are the dominant impacting parameters when the distance is shorter than 10 km. However, it is also noticed that the baseline distance has a more significant impact on the fix rate than the bandwidth and integration time when the distance is larger than 10 km, which could be caused by the simple DD measurement model we applied for the navigation filter. In addition, it was recorded that, for baselines shorter than 15 km, a fix rate of 90% was reached for all the settings combinations. The test results also show that a snapshot with the size of 255 kB could result in a potential fix rate of more than 93%, with centimeter level positioning accuracy when carrier phase ambiguities are correctly fixed. However, there is still a lot of unexplored potential in SRTK and better performance could be achieved with some further research. First of all, this work has a limited the number of satellites by using only GPS and Galileo constellations. With a more complete infrastructure network, more satellites from other constellations can be included in the RTK algorithm and higher fix rates are expected. Secondly, the ratio test could be implemented using LRF threshold values that adapt to a given failure rate, instead of directly comparing with the fixed value of two that is used in this research, the change of strategy could bring a big improvement in fix rate especially for the cases where the LRF values are close to the selected threshold. Thirdly, a more robust method can be developed for GPS satellites to solve the data bit ambiguity issue, the goal would be to remove the dependence on external navigation data bit services. Finally, more detailed performance evaluations about IAR and fix rate can be done by comparing the results with ground truth values derived based on a known baseline. Conceptualization, X.L. and M.A.R. ; methodology, X.L. ; software, X.L., M.A.R. and A.G.-A. ; validation, P.C., A.R.-G. and J.S. ; formal analysis, X.L. ; investigation, X.L. ; resources, A.R.-G. and J.S. ; data curation, M.A.R. and A.G.-A. ; writing-original draft preparation, X.L. ; writing-review and editing, X.L., P.C., A.R.-G. and J.S. ; visualization, X.L. ; supervision, M.A.R., A.R.-G. and J.S. ; project administration, P.C. ; funding acquisition, M.A.R., A.G.-A. and P.C. All authors have read and agreed to the published version of the manuscript. This research was funded by Albora Technologies and Universitat Politecnica de Catalunya with industrial PhD grant number DI 082 from the Generalitat de Catalunya; This research was partially funded by the Spanish Ministry of Science and Innovation project RTI2018-094295-B-100. P.C. has been partially supported by the NSF under Awards CNS-1815349 and ECCS-1845833. The study used data from ICGC and GFZ for generating the results. The GFZ data can be accessed through the URL [[http://isdc.gfz-potsdam.de](http://isdc.gfz-potsdam.de)]([http://isdc.gfz-potsdam.de](http://isdc.gfz-potsdam.de)) (accessed on 25 May 2021), project: GNSS, product type: GNSS-GPS-1-NAVBIT. The ICGC data can be obtained at [[ftp://geofons.icgc.cat/rinex3/](ftp://geofons.icgc.cat/rinex3/)]([ftp://geofons.icgc.cat/rinex3/](ftp://geofons.icgc.cat/rinex3/)) (accessed on 25 May 2021).