How can I read IONEX files in MATLAB?

I have some redundant information that I want to skip while reading this file and then I want to extract the latitude, longitude and TEC data into separate columns. I don't understand LAT/LON1/LON2/DLON either. Basically I need [x y TECdata] for Kriging.

[Walter Roberson]

With regards to the meaning of LAT, LON, DLAT, DLON:

The material I find indicates that the program used to generate that file was an older version of the source code available in http://ftp.izmiran.ru/pub/izmiran/SPIM/ in the isomain.zip file . In particular, file IRIPLAS5c.FOR there is noted as having comments about the format of the output file.

Answer 1

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/175097-what-is-the-fastest-way-to-extract-data-from-a-huge-text-file-urgent

[Sadia Khaf]

I checked this, it's not working for me. fopn and textscan seem to take the whole data as a single string.