Hans van der Marel, TU Delft, September, 2024.
UbxLogger is a suite of shell scripts and executables for logging data from a U-blox
ZED-F9P low cost GNSS receiver on OpenWrt routers and Single Board Computers such as the
Raspberry Pi.
Some of the things you can do with UbxLogger are
- Log data from one or more U-blox ZED-F9P receivers to a micro SD card, USB stick or disk partition
- Compress the data and save to an archive
- Optionally push the compressed to a remote server over the Internet (requires LAN, WAN or 4-G connectivity)
- Optionally convert the data to RINEX version 3 files, at a selectable sample rate and interval, Hatanaka and gzip compress, archive and/or push to a remote server.
- Start on (re)boot, monitoring and restart
You have have the choice to create compressed RINEX files on OpenWrt or SBC and push the RINEX to the remote server, and/or push ubx rawdata files to the remote server and convert to RINEX on the remote server. To transfer the compressed RINEX files, especially at a lower sample rate, requires only a fraction of the bandwith compared to ubx. A single receiver can produce up to 4 GB/Month of compressed raw ubx data if only raw measurements are stored (UBX-RXM-RAWX records). If also navigation data is stored (UBX-RXM-RAWX + UBX-RXM-SFRBX records) the number increases to 6 GB/Month. The RINEX data, at 10 sec sample rate, only takes less than 200 MB/Month.
UbxLogger is designed to run on power efficient OpenWrt routers and Single Board Computers.
In this document the hardware setup is described for two example configurations
- The GL-iNet X750V2 (Spitz) OpenWrt 4G router
- Raspberry Pi single board computer with Teltonika RUT240 4G router
First we need to configure the receiver.
UbxLogger uses the USB port of the ZED-F9P to power the receiver and stream data. The receiver must first be configured to send raw measurement data to the USB port. We use u-center for this task.
-
Connect the receiver to an USB port on your computer, start u-center and connect to the receiver using the proper COM port.
-
Open
View->Messages View, selectUBX-MON-VERin the left pane, and check that the firmware version is1.32or higher. If not, upgrade the firmware to version 1.32. -
Open
View->Generation 9 Configuration View, deselectSBASandQZSSif not needed, and send configuration to RAM+BBR+Flash -
Open
View->Configuration View- In the left pane select
MSG (Messages), in the right pane select02-15 RXM-RAWXand tickUSB, and pressSendin the taskbar. - In the left pane select
PRT (Ports), in the right pane select as target3-USBand changeProtocol outto0-UBX, and pressSendin the taskbar. This will disable NMEA output to the USB port, with as side effect that the time and satellite data in u-center is not updated anymore. - In the left pane select
CFG (Configuration), and pressSendin the taskbar. This will store the configuration in BBR and Flash.
- In the left pane select
-
Open
View->Packet Console, and check thatUBX RXM-RAWXmessages are send every second (and nothing else).
This will provide the minimal amount of information to generate RINEX observation files.
If you want you can also select to output 02-13 RXM-SFRBX so that also RINEX navigation files can be created.
However, this will generate a lot of additional data for something you can also download from other sources. To
save space, we recommend only to log 02-15 RXM-RAWX messages.
The GL-X750V2 Spitz is a 3G/4G dual-band wireless router running OpenWRT OS. It has built-in mini PCIe 3G/4G
module, built-in 128GB MicroSD capacity and USB-A port. Of course, it also has 2GHz/5GHz Wi-Fi, LAN and WAN
ports seen on most other routers.
Running on OpenWrt you can compile your own firmware and software to fit different application
scenarios.
This makes it an ideal controller for GNSS receiver boards, such as the U-blox ZED-F9P, which can be
directly connected to and powered by the USB-A port on the router. The ubxlogger scripts running on
OpenWrt saves the raw receiver data to the router's MicroSD card, optionally converts it into RINEX and
optionally send it to an upstream server using the 4G connection.
With an additional USB hub the router can log data from more than one receiver.
The GL-iNet router has three main user interfaces
- GL-iNet Web Admin Panel (http://192.168.8.1)
- OpenWrt LuCI web user interface (http://192.168.8.1/cgi-bin/luci)
- SSH to the router BusyBox ash shell (
ssh [email protected])
The first is a Grafical User Interface (GUI) for standard settings
and firmware upgrades. The second is a GUI for OpenWrt to do more advanced settings. Many
tasks can be done in both GUI's, but not everything. The third is a Command Line Interface (CLI)
which will be used for setting up regular Linux stuff and the ubxlogger software.
The GUI's are accessible with a web-browser on the local LAN after connecting to the router with a LAN cable or via WiFi. the WiFi password is *secret-1*. The admin/root password is *secret-2*. The GUI is also available remotely (over 4G) via the GoodCloud Cloud Management Software. The GoodCloud password is *secret-3*.
The ubxlogger software is managed through ssh. This can be done on the local LAN using
a ssh client (e.g. Putty on Windows) or remotely over 4G using ssh from the GoodCloud interface.
On the operational system WiFi is turned off to save power. To use WiFi on the local LAN you have first to enable it using a LAN cable or remotely through GoodCloud.
For more information on the GL-iNet Spitz see https://www.gl-inet.com/products/gl-x750/ or check out https://openwrt.org/start for working with OpenWrt. See also 2 for the installation manual.
This setup on a Raspberry Pi is pretty standard and not further discussed (The GL-iNet X750 is our preferred platform because of the lower power requirements).
In this section a short introduction to the UbxLogger software is given. The software is described in more detail in the UbxLogger Software Manual.
The UbxLogger software is written entirely as shell scripts. No Python, Perl, or other
interpreter tools are required. The reason for this is to reduce memory usage and be able to
runs it on OpenWrt routers with limited flash, ROM and RAM memory, while simultaneously be
able to run it on more powerfull single board computers like the Raspberry Pi.
The scripts have been written with BusyBox ash shell in mind. BusyBox was specifically
created for embedded operating systems with very limited resources and is used also by
OpenWrt. The scripts also run on the more powerful bash shell used by for instance
the Raspberry Pi and many other Linuxes.
In the background str2str from RTKLIB is used to capture data from the receiver. This can
be imported as extension package in OpenWrt. If not available for your system, it can
be cross-compiled on a Linux desktop using the OpenWrt developer suite and RTKLIB source
code. On the Raspberry Pi you can natively compile str2str with gcc from the RTKLIB source
code.
For the conversion to RINEX the convbin console app from RTKLIB and rnx2crx from
Yuki Hatanaka are needed. These can be compiled natively on the Raspberry Pi, or cross-compiled
using the OpenWrt developer package. It is also possible to convert the data to RINEX on an
upstream server, desktop or laptop using the same scripts.
All data files follow the RINEX3 file naming convention
SITE9CHAR_YYYYDDDHHMM_FFU_DDU_MO.{ubx|rnx|crx}[.gz]
All elements are fixed length and are separated by an underscore “_” except
for the file type (ubx, rnx or crx) and optional compression field (.gz)
that use a period “.” as a separator.
The 9 character station name SITE9CHAR consists usually follows the convention SITEMRCCC with a 4-character site name SITE (e.g.
'ZEGV', 'ROVN', ...), two decimals MR for the monument and receiver number, and the country code CCC.
However, you can use any naming convention as long as the total length does not exceed 9 characters, and you don't use _ or - in the name, as _ is reserved for
separating fields in the RINEX name, nor can we use - as this is very
awkward for shell scripting.
The software is managed through the ubxlogd script. The syntax is
./ubxlogd.sh [start|stop|check|restart|status] 'identifier'
./ubxlogd.sh status
./ubxlogd -h
The 9 character station name SITE9CHAR is used for 'identifier'.
For more details and other commands see the UbxLogger Software Manual.
This section is a shortened version from the UbxLogger Software Manual to provide an idea of the amount of data that is involved.
Under normal (full-sky) tracking conditions the typical amount ubx data that is collected, after compression with gzip, is
| RAWX | RAWX+SFRBX | |
|---|---|---|
| Hour | 4.2 MB | 5.7 MB |
| Day | 100 MB | 138 MB |
| Month | 3.0 GB | 4.1 GB |
| Year | 36 GB | 49 GB |
This is the amount of data that needs to be transmitted and stored.
As the navigation data (broadcast data messages send by the satellites) is the same for all stations, and can also be retrieved from the Internet, it is not necessary log SFRBX messages.
Therefore, storing only UBX-RXM-RAWX data for a single receiver will fill up a 128 GB micro SD
card in about 3 years, and requires a 4-5 GB data subscription with your telecom
provider.
Hatanaka compressed and gzipped RINEX version3 files tend to be smaller than u-blox raw data files. When the sample rate is further reduced to e.g. 10 seconds, the file sizes are only a fraction of the raw ubx data.
| intv | crx.gz | |
|---|---|---|
| Hour | 1 sec | 2 MB |
| Day | 10 sec | 4.5 MB |
| Month | 10 sec | 140 MB |
| Year | 10 sec | 1.6 GB |
Compressed navigation files are typically 300 KB per day.
Storing and transmitting compressed RINEX 3 data at 10 second sample rate takes only 1/20 - 1/30 of the data volume of raw ubx data.
The factory specifications for the different components are
| Device | Voltage | Idle | Typical | Max Dev | USB Amp. | Remarks |
|---|---|---|---|---|---|---|
| U-blox ZED-F9P | 5 V | 600 mW | n/a | Note 1 | ||
| ANN-MB-00 antenna | 3-5 V | 45 mW | n/a | |||
| 2B Survey antenna | 3-5.5 V | 150 mW | n/a | |||
| Raspberry Pi Zero W | 5 V | 500 mW | 750 mW | 850 mW | <2.5 W | |
| Raspberry Pi 3B+ | 5 V | 1.9 W | 5.0 W | 5.1 W | <6 W | |
| Teltonika RUT-240 | 9-30 V | 1.5 W | 4.2 W | <6.5 W | n/a | Note 2, 3 |
| GL.iNet X750V2 | 12 V | 4.5 W | <5.5 W | <3.5? W | Note 4, 5, 6 |
Notes:
- SimpleRTK2B, no radios, from ArduSimple
- Teltonika RUT240, Idle, is Mobile data on, no trafic, 12 Voltage
- Teltonika RUT240, Typical, Mobile data on, LAN, WiFi, trafic
- The GL.iNet X750V2 uses an uncommon barrel power connector outside/inside 4.0/1.7.
- From the GL.iNet forum, for older model GL-X750, system idle with 2.4Ghz Wifi running in STA+AP mode ~1.8W-1.9W (~150-160mA@12V), add 5.2Ghz AP brings it up to ~ 2.2 W (~180mA @12V), add cellular w/EP06 goes to ~2.3-2.4W(~190-200mA @12V).
- This number is not available from the GL-iNet specs. The USB 2.0 industry specifies a maximum current draw of 500 mA (2.5 W). On the GL-iNet forum there is one report that someone succesfully connect a USB modem (to an other device, not Spitz) with a power draw of 3.5 W.
The 6th column, "USB Amp" specifies the maximum possible power draw from the USB-A 2.0 port if such a port is available on the device. If a USB 2.0 port is not available on the SBC or router, the receiver must be powered using an external device.
Voltage and current are measured separately in the 12 V and 5 V circuits. For the 12 V circuit a DEWIN PZEM-013 DC 0-200 V 10A Digital Battery Tester, Power and Energy meter is used. For the 5 V circuit a USB 3.0 AT35 3.7-30V 0-4A digital Multimeter is used. Both instruments measure instantaneous Voltage (V), Amperes (A) and Power (W) and the consumed energy (Wh) over time.
Current and voltage is measured at two points
- The 12 V barrel connector of the GL.iNET X750V2, which gives the total power consumption
- The USB-A port of the GL-iNET between the GL-iNet and USB hub, which gives the power consumption of two U-blox ZED-F9P, two ANN-MB-00 antennas, and one USB-hub.
The second measurement (two U-blox ZED-F9P, two ANN-MB-00 antennas, and one USB-hub) is very stable
0.29 A @ 5 V -> 1.5 W for two receivers
Thus, the power consumption for a single receiver, with ANN-MB-00 antenna, is 750 mW, which is a bit more than what is given in the specs (645 mW).
The power consumption of two ZED-F9P receivers is also well below the limit USB-A 2.0 port can provide, so there is no need for external power supply.
The total power consumption is more variable. It is given in the table below for various scenarios
| Scenario | Current@Voltage | Power | Remarks |
|---|---|---|---|
| Full load | 360mA@12V | 4.4 W | Copying a tar file via WiFI |
| Logging 2+5G WiFi | 320mA@12V | 4.0 W | |
| Logging 2G WiFi | 280-300mA@12V | 3.4-3.7 W | |
| Logging no WiFi | 250-280mA@12V | 3.0-3.4 W |
The LAN cable was not connected. Also no clients connected to WiFi during the measurement. Turning WiFi off has a big impact. If necessary, it can be turned on again using the remote connection over the 4G network.
The 4G network was connected during all measurements, but without much trafic (No file transfers).
During a file transfer the power consumption peaks to 5.3W for very brief moments (with WiFi turned off). Also, during file compression with gzip, it seems there is a very small increase in power consumption (maybe 0.2 W), but hardly measurable because of the fluctuations.
To get a good impression on the average power consumption the power consumption was measured over a 24 hour period, with two receivers, and with WiFi turned off. The measured power consumption over a full day is 78.2 Wh, or 6.41 Ah @ 12.2 V, per day. This is equal to 3.25 W or 270 mA @ 12.2 V.
To summarize, with WiFi off, the total power consumption is well below 3.5 W .
If only one receiver, and no hub, is used the total power consumption is expected to be less than 2.7 W.
No measurements available yet.
The input parameters for the solar power and battery dimensioning are
SystemPower = 3.5 W
EquivalentSunHours = 1.08 hours
PowerRatio = 1.5
The equivalent Sun hours are for London, in December, south facing panels angled at 50°. The power ratio is to account for losses in the panels and charge controler.
The consumed power per day is
PowerConsumed = SystemPower * 24 hours = 3.5 W * 24 = 84 Wh per day
The minimal required panel power is then
PanelPower = PowerConsumed * PowerRatio / EquivalentSunHours = 84 * 1.5 / 1.08 = 117 Wp
Batteries are sized based on the number of days to run the device with Sunshine. The number of days the device can run on batteries alone is calculated As
NumberOfDays = BatteryCapacityAh * 12 * 0.9 / PowerConsumed
Here BatteryCapacityAh is given in Ah, the factor 12 is to convert Ah into Wh. The factor 0.9 is to account for the minimal discharce percentage of 10% for a battery.
For a 84 Wh power consumption per day, the number of days for two common battery capacities is
| Battery Capacity | No Sunshine |
|---|---|
| 30 Ah | 3.85 days |
| 50 Ah | 6.4 days |
Batteries should be sized to run the device for at least 4 days.
In order to be able to operate throughout the Month of December, we require at least (To be confirmed)
- 120 Wp Solar panels
- 50 Ah Lithium battery
Though a more practical sizing may be 60 Wp Solar Panels with a 30 Ah LiPo4 battery with a small amount of down-time in December.
| Part | Qnt | Price | Supplier | Remarks |
|---|---|---|---|---|
| SimpleRTK2B ZED-F9P | 1-2 | € 172 | ArduSimple | |
| u-blox ANN-MB-00 antenna | 1-2 | € 54 | ArduSimple | |
| USB-A to micro USB cable | 1-2 | € 3-8 | Alle kabels / Amazon | 1 |
| 4 port USB hub | 1 | € 5-17 | Alle kabels / Kiwi / Amazon | 1 |
| GL-iNet X750V2 EP06 | 1 | € 153 | Amazon | |
| SanDisk 128 GB HiEndu uSD | 1 | € 16 | Amazon | |
| 4G SIM card subscription | 1 | p/m | Telecom provider | |
| 12 V 5,5x2,1 male cable | 1 | € 2 | Amazon | 2 |
| 12 V 5,5x2,1 female cable | 1 | € 2 | Amazon | 2 |
Note 1: USB cables and hubs are widely available but their quality can vary. For good communication
between the receiver and router we advise to invest in good quality cables and hubs. Some recommendations are given in 2.
Note 2: The GL-iNet comes with its own DC connector and power supply. We recommend cutting the
cable and inserting a male/female 5,5x2,1 12 V DC connectors to ready the equipment for
battery and solar power.
The total cost for a setup with a single U-blox ZED-F9P receiver is about € 400. A setup with two U-blox ZED-F9P receivers will cost about € 600.
The monthly 4G subscription rate varies between € 10 and € 20 depending on the provider and data volume.
Four different USB hubs have been evaluated
| USB Hub | Price | Supplier | Remarks |
|---|---|---|---|
| USB Mini Hub w/ Switch | € 4.95 | Kiwi electronics | |
| KiWiBiRD USB 2-port spliter/hub | € 6.99 | Amazon | 18Month warrenty |
| Digitus USB2.0 Hub 4-port | € 7.39 | Alle kabels | |
| Nedis USB2.0 Hub 4-port | € 16.49 | Alle kabels |
The first USB hub, the USB Mini Hub with power switch from Kiwi electronics, was used for
the two week testing period and initial experimentation. During initial experimentation,
sometimes the data connection was lost - the USB contact don't feel very sturdy and are
easy to move in the sockets - but not the 5 V power, resulting in the assignment of a new
device name /dev/ttyACM#. This device was subsequently detected by the crontab hourly
ubxlogd check and logging to a new file started. During the 2 week test, the USB hub and
cables were left untouched and no interruptions occured. Our experiences with the first hub
prompted us to do a evaluation of alternative hubs and alternative USB cables to compare quality.
| Part | Qnt | Price | Supplier | Remarks |
|---|---|---|---|---|
| 120 Wp solar panel | 1 | € 90 | Eco-Worthy / Amazon | |
| 12V 50Ah LifePo4 battery | 1 | € 160 | Eco-Worthy / Amazon | |
| Solar charge controler | 1 | € 65 | Victron / Amazon | |
| Solar cable | 1 | |||
| Battery cable | 1 |
The total cost for solar panels and LifePo4 batteries is about € 320, but prices may vary depending on the chosen components. The quoted prices in the table are amongst the cheapest.
| Part | Qnt | Price | Supplier | Remarks |
|---|---|---|---|---|
| Antenna monument | 1 | |||
| Instrument cabinet | 1 | |||
| Solar panel mount | 1 |
1. H. van der Marel (2024), UbxLogger Software Manual, TU Delft, September 2024.
2. H. van der Marel (2024), UbxLogger GL-iNet Installation Guide, TU Delft, September 2024.