Comparison of GPS Modules: UBlox LEA-6H vs Blues Wireless Notecarriers

Last updated on Jan 18, 2024

Summary

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tl;dr the Blues Wireless Notecarrier v2 with chip antenna outperformed the active antenna (on an older notecarrier) and the Ublox LEA-6H module, likely due to the on-board filtering and maybe assisted GPSe.

Three tests were performed:

UBlox LEA-6H module vs. Notecarrier-Pi with Active Antenna
UBlox LEA-6H module vs. Notecarrier-A-v1.7 with on-board GPS Chip Antenna
UBlox LEA-6H module vs. Notecarrier-A-v2.0 with on-board GPS Chip Antenna

Analysis was done using the standard pandas, numpy, and matplotlib python libraries.

Generally the Ublox LEA-6H module

dropped less samples ✅
got a fix on more satellites ✅
was less precise / had a lot more jitter in the lat/long ❌ (sometimes on the order of 100m) - note though that I wasn’t applying any filters to the data
seemed more affected by worse weather or less-than-ideal placement inside. ❌

The Notecarrier modules

have much more “precision” (it probably does its own filtering and also might be using assisted GPS with the cell tower reads as well) ✅
was less affected by worse weather or indoor placement ✅
got a fix on less satellites at ❌
dropped more samples ❌

The old notecarrier with gps chip antenna (v1.7) and the notecarrier-pi with the active antenna were about the same, but the notecarrier-a v2.0 showed a big increase in precision.

Active antenna on the notecarrier pi shows more precision than the Ublox LEA-6H module

Note that below we go from a span of 4-10 meter errors to 0.85 to 1.10 meter errors. The LEA-6H histogram is not shown since it was ranging between 1 and 100 m.

The notecarrier-a v2.0 shows a dramatic increase in precision, and also dropped less reads than than the previous versions.

Improvement in Precision on Notecard Versions

Notecarrier Pi with Active antenna:

Notearrier A v2.0

Notecard Signal Dropped Comparison

Note we can’t really compare these because they were taken on different days, but look how the Notecarrier v2.0 drops less data samples.

Above: Dropped samples were replaced with error=0m so the red areas show us where samples were being dropped. Below: The notecard reports a signal value in dB, thus the the dropped samples appear a signal = 0dB

Above: The error of the notecard v2.0 is so low that is is squashed near to the x axis. Below: The notecard reports a signal value in dB, thus the the dropped samples appear a signal = 0dB .

Further

Test cold start time-to-fix
Add in bearing to get the directional skew (i.e. vectorize the error)

Appendix - Full Data

LEA-6H vs Notecarrier-Pi w/ Active Antenna

The error distance was calculated based on the distance from a “true” point picked on google maps, so at the <5m distance the “true” value may have been wrong.

The Notecard gps was much more precise with a smaller spread around the center. There is likely some filtering / averaging going on at the notecard level or they are using assisted GPS with the cellular tower data.

Summary for LEA:
Rows:  8639
Error Uptime (): 100.000000% (8639/8639)
Satellites Uptime (): 100.0% (8639/8639)
Summary for Notecard:
Rows:  8639
Error Uptime (): 97.789096% (8448/8639)
Satellites Uptime (): 100.0% (8639/8639)

Error/Distance Comparison

Left: Histogram and box plots of error (m). Right: Descriptive statistics of error. `df1` is LEA-6H, `df2` is Notecard.

Uptime

Here we plot the same graph as above (error), but showing “null” values as zero. We see the Notecarrier-Pi drops a lot more data. The bottom plot is the “signal” value that the notecard reports, we can see some of the signal values drop to zero for the notecard, even when the Ublox module has a fix.

Number of Satellites

Ublox module had more satellites more often (average of ~12 versus ~8 for the Notecard with active antenna)

LEA-6H vs Notecarrier-A-v1.7 w/ GPS Chip Antenna

Note that this test was done at a different location than the previous test.

Summary for LEA:
Rows:  8639
Error Uptime (): 100.000000% (8639/8639)
Satellites Uptime (): 100.0% (8639/8639)
Summary for Notecard:
Rows:  8639
Error Uptime (): 86.595671% (7481/8639)
Satellites Uptime (): 100.0% (8639/8639)

Error/Distance Comparison

Screenshot 2023-11-06 at 4.27.23 PM.png — Left: Error (m) histogram and box plot. Right: Summary statistics (`df1` is LEA-6H)

Uptime

Here we plot the same graph, but showing “null” values as zero. We see the Notecarrier-Pi drops a lot more data.

Summary:

LEA-6H Error Uptime: 100% (8639/8639)
Notecarrier-A-v1.7 Error Uptime: 86.595671% (7481/8639) i.e. ~1000 dropped datapoints

Number of Satellites

Same as before, Notecarrier gets a fix on less satellites

LEA-6H vs. Notecarrier-A-v2.0 w/ GPS Chip Antenna

Summary for LEA:
Rows:  8638
Error Uptime (): 99.120167% (8562/8638)
Satellites Uptime (): 99.12016670525584% (8562/8638)

Summary for Notecard:
Rows:  8639
Error Uptime (): 94.281746% (8145/8639)
Satellites Uptime (): 100.0% (8639/8639)

Error/Distance Comparison

The updated v2.0 notecarrier is very precise, so much that you can barely see its range of values when plotted on top of the Ublox module.

Zooming in on the “error” of the Notecarrier A v2.0 shows that its precise within 0.9 to 1.1 meters for all ~8k samples

Uptime

We still want to see the signal uptime for the notecard, which is also improved (less datapoints at 0dB SNR for the bottom plot).

The notecarrier v2 shows less dropped samples in bottom plot.

Satellites

The Notecarrier is still only looking at between 3-9 satellites on average.

Time series: