Question

The Ionobias software is giving me an error that I can't seem to solve. The error is "Least squares failed because the problem is singular" and appears near the end of my log file. I am inputting one RINEX observation file accompanied by it nav file. Below is a copy of my log file. Thanks in advance for the help.

IonoBias, built on the GPSTK ToolKit, Ver 1.0 6/25/04, Run 2013/07/12 18:49:01 Input configuration for IonoBias: Input Rinex obs file names are: chuc1440.13O Input Rinex nav file names are: chuc1440.13N AT file name is output Processing: Use a linear ionospheric model Minimum points per satellite = 0 Minimum time span = 0 minutes Minimum elevation = 0 degrees Minimum latitude = -90 degrees Maximum latitude = 90 degrees Minimum longitude = 0 degrees Maximum longitude = 360 degrees Time sector = night Terminal offset = 0 minutes Ionosphere height = 350 km Compute Sat+Rx biases Do not output biases to a file Do the estimation problem Do not skip the preprocessing End of input configuration for IonoBias SP3 Ephemeris list is empty Dump of GPSEphemerisStore: Span is 1741 396000.000 = 2013/05/23 14:00:00 GPS to 1741 446400.000 = 2013/05/24 04:00:00 GPS with 43 entries.

Process 1 input files:

Opened input file #1: chuc1440.13O File name: chuc1440.13O Marker name: chuc Position (XYZ,m) : (0.000, 0.000, 0.000) Position (LLH ) : (0.00000000, 0.00000000, -6378137.0000) Observation types (5) : C1 L1 L2 P2 P1 Time of first obs 2013/05/24 00:00:00.0000000 GPS Time of last obs 2013/05/24 00:59:59.0000000 GPS DOY = 144 Sunrise = 4.76 Sunset = 19.24 Begin time = 19.24 End time = 4.76 PRN Points Timespan Begin End (hrs) G01 3600 1.00 0.00 1.00 G07 106 0.03 0.00 0.03 G08 3600 1.00 0.00 1.00 G09 3600 1.00 0.00 1.00 G11 3600 1.00 0.00 1.00 G15 3469 0.96 0.00 0.96 G17 3600 1.00 0.00 1.00 G19 319 0.09 0.00 0.09 G24 2998 0.83 0.17 1.00 G26 1870 0.52 0.00 0.52 G28 3600 1.00 0.00 1.00 G32 454 0.13 0.87 1.00

Processed 1 files; 1 of them had good data. Total number of data points = 30816 Found 90.00 <= raw Lat <= -90.00 and 360.00 <= raw Lon <= 0.00

Opened AT file output for input 1 Number of stations (N data and filename follow). 1 chuc 30816 010000011101000101010000101010001 chuc1440.13O Robust statistics: Number = 30816 Quartiles = 0.00000000 0.00000000 Median = 0.00000000 MAD = 0.00000000 Outliers (low) = 0 Outliers (high) = 0 0.00 Minimum Latitude 0.00 Maximum Latitude -7.50 Minimum Co-rot lon 7.50 Maximum Co-rot lon 30816 data points used.

Opened AT file output for input Model is linear 1 Number of stations (N data and filename follow). 1 chuc 30816 010000011101000101010000101010001 chuc1440.13O 0.00 Minimum Latitude 0.00 Maximum Latitude -7.50 Minimum Co-rot lon 7.50 Maximum Co-rot lon 30816 data points used.

Least squares failed because the problem is singular

IonoBias timing: 1.775 seconds.

-- AnthonyMcCaffrey - 12 Jul 2013

Answer

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Anthony,

Sorry about the delay in responding to your question.

Normally, if the "Least squares failed because the problem is singular" error occurs in IonoBias, its because there are not enough stations or the distribution of stations does not contain enough diversity.

Per IonoBias.cpp - "Program IonoBias will estimate satellite and receiver biases and compute a simple ionospheric model using least squares and slant TEC values from multiple stations."

Looking at your log file, it looks like the number of stations is only 1 based on "1 Number of stations (N data and filename follow)", which will produce the Least Squares error.

In order to solve the error, you will need to provide an observation file with data from multiple stations.

I hope this helps with your problem, and thanks for your interest in the GPS Toolkit.

-- BryanParsons - 06 Aug 2013 No such template def TMPL:DEF{PROMPT:supportquery}

Topic revision: r3 - 12 Jun 2015, UnknownUser
 

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