ubx-cfg
Static ESP Testing - Phase 3
Overview
The objective of phase 3 was to determine the effects of limiting the number of satellites @ 15 Hz. The SYRAC GPS devices were configured to use GPS + Galileo + GLONASS or GPS + Galileo + BeiDou B1C, and various satellite limits - 20, 24, and 28.
The tests were started on 2026-07-10 @ 2311 and the duration was close to 12 hours. The results re-enforced the belief that B1C is better than GLONASS, and also showed that satellites limits can prevent dropped frames, without reducing accuracy.
Configurations
The following device configurations were tested.
| ID | Constellations | Rate | Max Sats | ESP | Observed time distribution (ms) | Drops? |
|---|---|---|---|---|---|---|
| D3 | GPS + Galileo + GLONASS | 15 Hz | 28 | 240 MHz | 65: 1, 66: 2844, 67: 623883, 68: 2855, 133: 9 | Y |
| D5 | GPS + Galileo + BeiDou B1C | 15 Hz | 28 | 240 MHz | 66: 2838, 67: 623969, 68: 2842, 133: 4 | Y |
| D1 | GPS + Galileo + GLONASS | 15 Hz | 24 | 240 MHz | 65: 1, 66: 2845, 67: 623816, 68: 2854, 132: 1, 133: 5 | Y |
| D2 | GPS + Galileo + BeiDou B1C | 15 Hz | 24 | 240 MHz | 66: 2288, 67: 502609, 68: 2290, 133: 2 | Y |
| SY1 | GPS + Galileo + GLONASS | 15 Hz | 20 | 240 MHz | 66: 2806, 67: 623919, 68: 2806 | - |
| S3 | GPS + Galileo | 15 Hz | 20 | 240 MHz | 66: 2835, 67: 623912, 68: 2835 | - |
| SY2 | GPS + Galileo + GLONASS | 10 Hz | 32 | 160 MHz | 99: 21, 100: 417730, 101: 43, 199: 23, 200: 1987, 201: 1 | Y |
Notes:
- S3 was intended to be GPS + Galileo + BeiDou B1C, but it somehow switched to GPS + Galileo
- All of the devices using more than 20 satellites dropped some frames, but SY2 dropped a LOT of frames
Statistics
Click the GPY filenames for charts showing SOG, Sats, HDOP, and sAcc.
| File | Description | Mean | Median | Stddev |
|---|---|---|---|---|
| SY2_2607102311.gpy | GPS + Galileo + GLONASS, 32 sats @ 10 Hz | 0.046 | 0.043 | 0.025 |
| D2__2607102312.gpy.gpy | GPS + Galileo + BeiDou, 24 sats @ 15 Hz | 0.051 | 0.047 | 0.027 |
| S3__2607102311.gpy | GPS + Galileo, 20 sats @ 15 Hz | 0.052 | 0.049 | 0.028 |
| D5_2607102311.gpy | GPS + Galileo + BeiDou, 28 sats @ 15 Hz | 0.053 | 0.049 | 0.029 |
| D1_2607102311.gpy | GPS + Galileo + GLONASS, 24 sats @ 15 Hz | 0.053 | 0.051 | 0.028 |
| SY1__2607102311.gpy | GPS + Galileo + GLONASS, 20 sats @ 15 Hz | 0.054 | 0.051 | 0.029 |
| D3__2607102311.gpy | GPS + Galileo + GLONASS, 28 sats @ 15 Hz | 0.057 | 0.052 | 0.031 |
GPS + Galileo + BeiDou (green) slightly outperformed GPS + Galileo + GLONASS (orange) with 24 satellites.
GPS + Galileo + BeiDou (green) slightly outperformed GPS + Galileo + GLONASS (orange) with 28 satellites.
GPS + Galileo + BeiDou (green) slightly outperformed GPS + Galileo + GLONASS (orange) @ 15 Hz from the perspective of median values.
The performances from the perspective of standard deviation were ordered in much the same way as the mean values.
Observations
- S3 was intended to be GPS + Galileo + BeiDou B1C
- Somehow it was switched to GPS + Galileo
- 38,400 baud was able to cope with a sample rate of 15 Hz
- SY1 did not drop any frames, despite running at 38,400 baud
- All of the devices with more than 20 satellites dropped frames
- SY2 dropped a LOT of frames, perhaps because max sats was 32
Conclusions
- B1C is clearly better than GLONASS, certainly at this latitude
- B1C outperformed GLONASS regardless of max sats = 24 or 28
- Sadly no data for 20 sats, due to incorrect configuration on S3
- Reducing max sats does not necessarily reduce accuracy
- 24 was the most accurate @ 15 Hz
- 28 was the least accurate @ 15 Hz
- Reducing max sats can potentially prevent dropped frames
- 20 had no dropped frames, but without any reduction in accuracy