UM980 is relatively affordable chip allowing multi-constellation multi-frequency GNSS with capability to provide raw phase measurements and hence potentially suitable for use in OpenStreetMap environment for precise mapping susing RTK.

In this post (or potentially series of posts), I will document my experiences with using UM980 with RTKLIB and other open-source or free tools.

Hardware

• UM980 RTK GNSS USB Dongle with SMA antenna - ELT0222 (from gnss.store)
• EM-FD700 antenna (form AliExpress)

The module can easily be configured using UPrecise tool coming with UM980. It is advisable to have faster than default COM port rate ~~~ CONFIG COM1 230400 ~~~ and use the signal group 2 (note that this leads to reset of the UM980 module ~~~ CONFIG SIGNALGROUP 2 ~~~

If you need to stop the stream of measured data, you can use ~~~ UNLOG ~~~ You can also UNLOG just specific messages.

If you want to store your config of the module so that it survives unplugging and restarting the module, use ~~~ SAVECONFIG ~~~

Software setup on Android

RTKGPS+ - collecting raw phase measurements

This is to collect the raw data in real time. The last RTKGPS+ tool is release is unfortunately relatively old and hence does not support, so the native UniCore support, which is available in demo5_b34L version of RTKLIB, is not yet available in RTKGPS+. Hence it is mostly useful for collecting raw data, rather than providing real-time solutions. If you want to collect the data, choose BINEX as the format and just log the input stream from the USB. This is how to configure the module:

CONFIG PPP DISABLE

OBSVMB 1

GPSEPHB 120
BDSEPHB 120
BD3EPHB 120
GLOEPHB 120
GALEPHB 120

GPSIONB 120
BDSIONB 120
BD3IONB 120
GALIONB 120

If you want to have faster measurements, you can use ~~~ OBSVMB 0.2 ~~~ But it may be then advisable to use at least 240kbaud rate of the COM port (which is generally well supported by RTKGPS+).

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