Skip to main content

How to log data for OPUS

Get the how-to cards on your smartphone to work in the field

This guide shows how to record logs for NOAA's Online Positioning User Service (OPUS) and download them using Emlid Flow.


Online Positioning User Service (OPUS) is provided by the National Oceanic and Atmospheric Administration (NOAA). With OPUS, you may accurately determine the coordinates of a static point mostly on the territory of the US without real-time corrections or a base station nearby.


You can learn more about the NOAA’s OPUS in this guide.

Recording RINEX logs on Reach

To record logs for OPUS, follow the steps below:

  1. Open Emlid Flow and connect to your Reach.

  2. Go to the Logging screen.

  3. Tap the Recorded logs and settings button.

  4. To configure logging, tap the Settings button.

  5. Select the OPUS preset.

  6. Choose the required RINEX format in the Raw data section.


    If you do not know which version of RINEX you need, we recommend using RINEX 3.03.


    While recording in the RINEX format, you can log the UBX file as a backup. UBX file can be used to adjust RINEX file settings in the Converter tool in Emlid Studio. You can enable logging in the UBX format in the logging settings in Emlid Flow.

  7. Tap Show configuration and enter the measured height to the bottom of the receiver in the corresponding field.

  8. Fill in the point's name in the Marker name field.

  9. Tap Apply.


    You can start recording automatically when your receiver is turned on. Check the corresponding field on the Raw data settings screen.

  10. Enable log recording by tapping the Start recording button. The red recording icon will appear in the status bar.


    NOAA’s OPUS requires recording the data for at least 4 hours to get the best accuracy.

  11. To finish recording logs, tap the End recording button.


Wait for data processing to finish.


You may log the data for up to 24 hours, depending on the accuracy required.

Once you finish the survey, don't forget to turn off raw data recording in the logging settings.

Downloading logs

After you finish raw data logging, you need to download RINEX data from Reach to your mobile device.

  1. Go to the Recorded logs section at the bottom of the Logging screen.


    You can also find information on the logs size and recording date and time here.

  2. To export the file, tap the Download button.

  3. Save your log depending on the device you use.


    If you do not need your logs anymore, you can delete them using the Select button.

When the logs are downloaded, you can submit the data to NOAA's OPUS for processing.

Further reading