CNRDIFF

A library used to compare signal-to-noise ratio for GNSS observation data.

Dependencies

• pandas >= 2.0.0
• pyrtcm >= 1.0.0

Usage

Compute carrier-to-noise ratio differences of stations SN04 and SN02 relative to reference station SN01:

cnrdiff SN01001a.24O SN02001a.24O SN04001a.24O

Optional arguments

Compute differences by satellite system and save the output to a file:

cnrdiff --ftype RTCM3_MSM4 a.rtcm b.rtcm --by-sys > result.txt

Supported file types and auto-detected suffixes:

Use --ftype to override auto-detection when needed.

Averaging algorithm

Assumptions

1. Each station records observation data normally, with no missing epochs or event interruptions.
2. Observation data from all stations is time-synchronized, with start and end times as consistent as possible.
3. The epoch interval of observation data does not exceed 1 second; data is processed as 1-second intervals.

By satellite PRN (default)

The intermediate CNR binary file generated during execution is an SQLite database that stores the carrier-to-noise ratio for each epoch, each satellite, and each signal type.

1. First, compute the average of each signal type over all epochs for each satellite to obtain a table indexed by satellite PRN and signal type.
2. Then align the tables from all stations and compute differences to obtain a table indexed by satellite PRN + signal type and station (data file name).

By satellite system

Extract the satellite system from the satellite PRN as a new dimension.

1. First, compute the average of each signal type over all satellites and all epochs for each satellite system (equivalent to a weighted average by epoch count per satellite) to obtain a table indexed by satellite system and signal type.
2. Then align the tables from all stations and compute differences to obtain a table indexed by satellite system + signal type and station (data file name).

License

MIT

Authors and contributors

Lead Programmer: Sheng Guoliang shengguoliang@sinognss.com

Contributors:

• Yang Fawang yangfawang@sinognss.com