Where can I process the single frequency GPS data
1) by Klobuchar model
2) by introducing my TEC data (as calculated from the in-situ dual frequency GPS),
3)by introducing any global TEC data, i.e., the .ION files published by CODE, UNIB
So that I may compare them and see how the position coordinate varies with each option.
If anybody has an idea about this aspect, I would be glad to hear from you.
Thanks and regards,
sampad
I think it is not possible to obtain TEC from single frequency, but you can quantify the delay if you correctly know the position of the satellite and use it to just approximate TEC. so you have to therefore where your satellite are and use that as abasis of computing your delays hence TEC
@ Dr. Olwendo, Thank you sir. But, what I mean is I have the TEC as derived from the dual frequency data. Now, I want to use this TEC data for ionosphere error correction in the single frequency receiver exactly at the same location where the dual frequency TEC was calculated. So, is it possible with any package or program in which we can incorporate the VTEC value as estimates of ionosphere error and thereby determine the position of the single frequency receiver.
Your comments in this thread are welcome
regards,
sampad
@Venkata Ratnam sir, Yes you are absolutely correct. Please, let me know if it is possible to do this task.
regards,
sampad
I get your question now. that should be possible and i will check again in the internet and get you some specific tools which are open source for this sort of thing. if you are interested i also have a code which process TEC from a dual frequency and converts TEC into ionospheric errors that is vertically, horizontally north and east ward. how this can help you am not sure!
You can introduce the ionospheric models in Leica Geo Office software as follows:
Configure GPS Processing > Strategy > ionospheric model
To use Global model the IONEX file should be in the your LGO project directory
For Klobuchar model there should be the coefficients Alpha_i and Beta_i of the model in the navigation messages.
The Ionosphere is a predominant source of error in the GNSS Receivers and it acts on the code and carrier based pseudoranges in a opposite way. The code is delayed and the carrier is advanced (the phenomenon of code carrier divergence) which happens when GNSS signals pass through ionosphere. Normally using a single frequency receiver it is not possible to estimate the iono error properly. So there exists models like the Klobucar Model (which uses four alpha and Beta coefficients) which is a generalized model and using that 50% iono error approximately may be estimated. In countries like India which is close to equator a GRID based Ionospheric model is also proposed for IRNSS. If you have a dual frequency Receiver then you can certainly measure the iono delay.
Once to have that and want to use this info for Single frequency receivers you need to adjust the pseudo rage measurements obtained from single frequency receivers which the actual iono data you have and derive the ionospheric free pseudoranges. hen if you have the satellite positions available for that measurement time you can estimate the User position.
Hope it helps. All the best for your Research.
I would suggest you investigate the open-source package for GNSS positioning, called RTKLIB (www.rtklib.com). It allows you to process your single-frequency observation data, as well as to input your IONEX files for the ionospheric corrections. In case you want to process your data with the Precise Point Positioning (PPP) method, I inform you that RTKLIB does not support single-frequency PPP (SF-PPP) due to the fact that the package does not allow you to process only the L1 data. However, you can modify the source of RTKLIB (as it is a open-source package), and implement SF-PPP by your own.
Another package you could use, in case you need SF-PPP, is the PPP-Wizard (http://www.ppp-wizard.net/index.html) which supports the PPP method using single-frequency observation data and IONEX files.
I hope it helps. If you have further questions, I would be glad to help you.
I have another suggestion for you that will help you to process your data. You can download the gLAB tool suite from:
http://gage.es/forum/software-tools
It can be run either Windows, Linux or MAC. It has the versatility to process in Standard Point Positioning (SPP) and Precise Point Positioning (PPP). The 1st processing you want to do is straight forward with the gLAB tool using the SPP template. The 2nd one also with the PPP template. For the use of the IONEX TEC source, since the gLAB offers its source code, you could adapt the SPP to get the TEC corrections from IONEX files (conveniently interpolated) instead of using Klobuchar.
