Opening 21O Files

The 21O file type is primarily associated with Assistant.

21O	File extension: 21O
	File type:	GNSS Observation Data

What is a 21O file?

21O files mostly belong to Assistant. A .21O file is a GNSS observation data file primarily used by Assistant, a software related to RTKLIB. It stores raw GNSS measurements collected by receivers, including signal information like pseudorange, carrier phase, Doppler shift, and signal-to-noise ratio. These measurements are crucial for various positioning and navigation applications. The internal structure of .21O files closely resembles the standard RINEX observation data file format, facilitating interoperability with other GNSS processing software.

How to open 21O files

You need a suitable software like Assistant to open a 21O file. You need a suitable software like Assistant to open a 21O file. Without proper software you will receive a Windows message "How do you want to open this file?" or "Windows cannot open this file" or a similar Mac/iPhone/Android alert. If you cannot open your 21O file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a 21O file directly in the browser:. Just drag the file onto this browser window and drop it.

Online 21O Text Viewer

Choose your .21o file to view

or drag and drop it here

Online File Viewer

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How to extract texts from 21O files or capture a screenshot to PDF, JPG, DOCX, TXT, ...

If you want to extract texts from 21O file or capture a screenshot, you can use our free Online 21O File Viewer:

To do this, click the button "Choose your .21o file to view" on this page.
Your 21O file will then be displayed in the browser.
Now click on "Save as..." at the top of the page.
Then choose the file format (e.g. JPG, PDF, DOCX, TXT, ...) you want.
Download the converted file.

Unable to Open a .21O File? Quick Solutions:

21O files can originate from various GNSS systems and aren't universally openable.

Identify the Source: These files typically come from surveyors or GPS receivers logging observation data for the year 2021.
Check the Header: Open the file in a text editor to inspect the first lines. You may see:
- Plain text starting with RINEX VERSION, confirming standard RINEX data.
- Unreadable binary symbols, implying a proprietary compressed format.
Use the Original Software: You usually need specialized GNSS processing tools. Try software like Assistant, RTKLIB, or Trimble Business Center, or ask the sender.
Use this Webpage: Drag and drop your file into our viewer to detect its format, extract readable metadata, and preview the contents.

Technical Data for 21O File Extension

File classification:

GNSS Data File

Related files:

210, 21, 21n, gut, vis, tbk

a 21o GNSS Observation Data is a special file format and should only be edited and saved with the appropriate software.

How to solve problems with 21O files

Associate the 21O file extension with the correct application.
Update your software that should actually open gnss observation data files. Because only the current version supports the latest 21O file format. Search, therefore, e.g. on the manufacturer website after an available Assistant update.
To make sure that your 21O file is not corrupted or virus-infected, get the file again and scan it with Google's virustotal.com.
Click here to open your .21O file online - secure, fast, and no downloads needed.