Dear Mourtadha Sarhan Sachit ,

Among GNSS processing services, the Double Difference (DD) algorithm tends to be always better than Precise Point Positioning (PPP).

This is because PPP is only considered the observables collected by a single receiver during a certain time of tracking.

It is obtained more accurate results when the relative positioning is carried out, that is, where a pair of receivers (Base and Rover) collect information from visible satellites simultaneously. The mathematical model of the Double Difference of the observables eliminates the clock errors of the satellites and receivers and minimizes atmospheric errors in short baselines.

With regard to the tracking time, the PPP becomes more precise the longer the time, due to the large amount of observables and variations in the GNSS constellations during the day (not counting the variations in the atmosphere, ionosphere, etc.).

For engineering projects that require accuracy and precision better than 1 meter, I suggest using the DD algorithm using professional geodetic receivers. The tracking time and distance from baselines will depend on the precision required in your project.

Thank you Mr. Leandro França for the answer ...

Really, it is common knowledge that DD method is better than PPP. But in areas that do not have a good distribution of IGS stations, and the observation time period is less than two hours. Do you think that the DD method will achieve better accuracy than the other ?

Thanks for your generosity information.

You're welcome Mourtadha Sarhan Sachit ,

I'm pretty sure DD will achieve better results than PPP.

Generally each country has its densified network of continuous GNSS tracking stations with adjusted coordinates (or known coordinates), i.e., an official geodetic reference system.

IGS network stations are really scarce, when you want to work with a short baseline and reduce tracking time.

One suggestion is to track a vertex (Base) for a longer time (for example, 4 hours) and simultaneously track other vertices for 15 min (Semi kinematic Method - Stop and Go), with baselines smaller than 20 km. With this method you can achieve accuracy better of a few centimeters.

If the Base has known coordinates, then you can apply directly the DD method, but if it is not known (which happens in most cases), you should perform static relative processing with the closest stations of the geodetic network in your region.

It's a little complicated to explain everything with a few words, but I hope you have understood the main idea.

I suggest consulting the following book:

Satellite Geodesy, 2nd Ed. Günter Seeber

It covers very well all these methods of positioning.

Thanks for your detailed answer.

I am currently conducting a research with colleagues on this matter .. When completed, I will share it with you.

Regards