# Assessment of IRNSS-Only Data Processing: Availability, Single-Frequency SPP and Short-Baseline RTK
###### Abstract
The accuracy assessment of SPP with IRNSS L5, S, and L5/S signals indicated that the horizontal offset between the reference point and the average value of the epoch-wise position solutions for the three cases was 1.571, 0.398, and 0.372 m, respectively, while the corresponding three-dimensional (3D) offset was 1.706, 1.526, and 1.461 m, respectively. With the continuous improvement of the IRNSS constellation, several researchers have begun to consider the interoperability of IRNSS with other satellite systems. [PERSON] et al. [9] analyzed the positioning performance of seven-satellite IRNSS and the combination of IRNSS with GPS and GLONASS by using simulation methods. Based on the simulated PDOP values and UERE values (approximately 6 m), it was deduced that the position accuracy achievable with IRNSS satellites was at the level of 20 m over the Indian subcontinent, while the corresponding position accuracy was improved to 6-8 m under the combination of GPS/GLONASS/IRNSS. ISRO [10] analyzed the accuracy of dual-frequency SPP, and the performance of DOPs and available satellites by dividing the IRNSS service areas into five regions (eastern, northern, western, southern, and central). [PERSON] et al. [11] solved the short baseline based on the combination of IRNSS and QZSS. The results showed that the ambiguity success rate (ASR) for a single system (i.e., IRNSS or QZSS) was both under 10%, but the ASR could reach up to approximately 100% after using the combination of IRNSS and QZSS. Additionally, the IRNSS/QZSS integrated case could achieve smaller PDOP values, and the positioning accuracy was at a millimeter level in the east, north, and up directions when the phase ambiguities were successfully fixed. The combination of GPS/Galileo/QZSS/IRNSS could significantly improve the ASR and positioning performance under high cut-off elevations when using the L5 signal [12]. The ASR of the four-system combination was higher than 95% even when the elevation mask was set to 40 deg, with the millimeter-level and decimeter-level positioning accuracy under ambiguity-fixed solutions and ambiguity-float solutions, respectively. [PERSON] et al. [13] combined the systems of IRNSS, GPS, Galileo, and QZSS to evaluate the relative positioning accuracy with the single-frequency observations from L1/E1 or L5/E5a signals. The single-frequency ASR of L1/E1 and L5/E5a signals were 74% and 96%, respectively. The positioning accuracy with L5/E5a signal was slightly better than that with L1/E1 signal under the ambiguity-fixed solutions, and the advantage of L5/E5a signal was conspicuous under the ambiguity-float solutions. The results demonstrated that the L5/E5a signal had a better positioning performance than the L1/E1 signal for all the satellite systems. [PERSON] et al. [14] observed ASR improvements of 26.2%, and 57.7%, respectively, in classical differencing and inter-system differencing when only 3-4 IRNSS satellites were added to GPS/Galileo/QZSS for L5/E5a short-baseline positioning. Although many previous studies evaluated the positioning accuracy with IRNSS, the IRNSS performance at the user end needs to be further investigated. For single-frequency SPP performance analysis, only one or two stations were employed in [7; 8], and the theoretical analysis with PDOP and URER rather than the real data processing with ground tracking stations was conducted in [9]. In addition, the accuracy of dual-frequency SPP was investigated in [10], but the SPP users usually employ the single-frequency observations. With the increasing number of Multi-GNSS Experiment (MGEX) stations that can receive the signals of IRNSS, the earlier SPP results may no longer be applicable. As to the real-time kinematic (RTK) positioning performance analysis, the existing research [11; 12; 13; 14] paid more attention to the fusion data processing of IRNSS with other satellite systems, and only limited IRNSS-only solutions with low ASR were reported in [11; 12]. Thus, more tests should be carried out to gain more insight into IRNSS-only RTK performance.