2022august 26

Allow up to 72 satellites per epoch (it was 60)


2020november 27
Ignore satellites with values of 99999.999  ....

2020august 19
Check for nonsense SNR values. If larger than 999, write out as zero.

20apr03
I have extended the capability of this code to read
up to 25 observable types in a RINEX 2.11 file.  The code will exit
beyond this point. If you have more than 25 obs types,
I recommende using a program like teqc to reduce the number
of observables, e.g.

teqc -O.obs S1+S2+S5 inputRinex > outputRinex


The program gfzrnx can similary reduce the number of observables.

Sincerely,
Kristine M. Larson


19oct18
To clarify, the column definitions are:

1 Satellite number (see **)
2 Elevation angle, degrees
3 Azimuth angle, degrees
4 Seconds of the day, GPS time
5 elevation angle rate of change, degrees/sec.
6  S6
7  S1
8  S2
9  S5
10 S7
11 S8

Units of the SNR observables are the same as the native RINEX file

**
Satellites are named as follows:
GPS 1-99
Glonass 101-199
Galileo 201-299
Beidou 301-399

SNR Options:
options 98 and 99 are all data wth elevation angle between 5-30 degrees 
option 88 is all elevation angle data above 5 degrees
option 66 is all elevation angle data below 30 degrees
option 50 is all data below 10 degrees

Allows up to 20 observables in the RINEX file

gfortran is used in the makefile
-----------------------------------------------------------------------------------------------
Using gfortran for the executable 

Unknown date
Allows 20 observables

19feb04
The code has been changed to allow a sp3 file to be longer than 23 hours and 45 minutes.
This was a pretty major change because I had to allow for the sp3 file to change GPS week 
on midnite, which meant changing the timescale used (previous gps seconds and now seconds relative
to the sp3 epoch).  Other minor changes were made to improve commenting.
Let me know if you see odd behavior.

19jan10
Various updates, including extending the number of allowed observable types to 20.
(it was previously 15).
We now allow up to 60 satellites at one epoch can be reported (up from 48).

makefile now uses gfortran instead of local f77 command I had been using.

Because of the size of RINEX files, I only provide a single test file with 
only two epochs.  A sp3 file with signals from all four constellations is also 
provided. 

shellscript testit will show you the input and output of the code.

-----------------
18oct01 
I added space for observables s6,s7,s8, I am currently storing s6 in column 6
and s7 and s8 are in new columns: 10 and 11.  As with GPS, S5 for Galileo is still stored
in column 9.  Column 5 is still edot.  Beidou is stored in the S2, S6, and S7 slots

18oct16 
I increased the number of satellites allowed at any epoch from 36 to 48
This allows multiple constellations without having to make separate
files.

May 14, 2018

This code is meant for sp3 files from midnite to midnite (minus epoch), where
epoch is the sample interval (usually 15 minutes).  Some sp3 files 
apparently have two midnites.
The code has been modified to only read the orbit positions for the same day
as the day in the header. So the second midnite is ignored.

This code is not meant for sp3 files which cross midnite. 


January 8, 2018
This is a new GNSS version of RinexSNR. The original used navigation
messages and was restricted to L1 , L2 and L5 GPS signals. This version
allows all GNSS constellations (GPS, GLonass, Galileo, and Beidou).  
To accommodate this change, I am now using sp3 files for the orbits.  

The a priori receiver coordinates can be changed by modifying 
the locations and velocities in the knut.txt file.  
If your site is not defined in that file, the code uses the RINEX header location.
This option is particularly useful for Antarctica and Greenland.
The location of the file is hardwired. Please change the locaction of the filename in the
moving_sites.f file before you compile the code. 

To test that you are getting the correct answers, use the examples in testit,
or  
             input        output    sp3file    option
gnssSNR.e smm32960.17o  out-smm3A gbm19721.sp3 98
gnssSNR.e smm32970.17o  out-smm3B gbm19722.sp3 98

option 98 and 99 are data between 5-30 degrees (98 was defined to facilitate for testing with RinexSNR)
option 88 is all data above 5 degrees
option 50 is all data below 10 degrees
an old option (77) for L2C only satellites is not currently set for this code.

To accommodate reflector height corrections which need d(elevation angle)/ dt,
the 5th column now has this value, in degrees/sec.
The 6th column is not meaningful

Column 7,8,9 are SNR signals for L1, L2, and L5

Satellites are defined as follows:
GPS 1-99
Glonass 101-199
Galileo 201-299
Beidou 301-399

Please let me know if you find bugs.

Sincerely,
Kristine M. Larson


-----------------------------------OLD CODE -------------------------------


June 5, 2015

RinexSNRv2 extracts SNR data from RINEX files (version 2.11)
It computes a simple azimuth and elevation angle
for easy reading into other programs, i.e. Matlab.

Output format:
satellite number, elevation angle, azimuth angle, secondsOfday 
east and north multipath reflection points (in meters) for a 
2 meter antenna and S1 S2 values in the original RINEX units, usually db-Hz

The options are easy to see in the code. Option 77 is all data for L2C only satellites.
As new satellites are launched, you need to add their names to the code.
Option 99 is for all satellites, but only below 30 degrees. Option 88 is all
satellites, all data.


I cut off at 5 degrees because I have found the data can have 
large outliers below this value, but you are welcome to modify the 
code for your own interests.

To run:
 
RinexSNRv2.e inputRinex outputSNRfileName navfile program-option

----

1. This version replaces the previous one that had a bug in the 
ephemeris calculation.  In fixing that, I took the opportunity to rewrite the code
in a more modular form. I hope this makes it easier for others to 
understand. 

2. This code ignores everything except GPS data.  If someone is willing
to give me fortran code that will calculate the orbit for a GLONASS
satellite, I am willing to modify it.

3. I do not think this code allows more than 24 satellites at a 
given epoch. I don't think that will be hard to fix, but currently the 
program exits if it finds more than 24 satellites.

4. There is a limit to the number of observables. You can use teqc
to reduce the number of observations if you run into that limitation.

5. I'm sorry but I do not speak PC. I cannot make a PC executable for you.

I would be very grateful for bug reports.

Sincerely
Kristine M. Larson
University of Colorado