Before GPR surveying we have to set step of acquisition in Synchro program settings:

We got different GPR profiles with different values of Step of acquisition.
See the results below:
 
Pipe3.sgpr GPR profile: Step of acquisition is 26,03 mm.
Initial proportionality: one pixel is equal to one sample

 
Pipe2.sgpr GPR profile: Step of acquisition is 156,18 mm.
Initial proportionality: one pixel is equal to one sample

It would seem that using smaller value of Step of acquisition we would get more detailed GPR profile.

However, if you change proportionality from samples to distance, you will see that the resulting GPR profile is very similar to Pipe3.sgpr GPR profile. (Click button Distance 1:1, located in the GPR profile window, View tab. See picture below)

   
Pipe3.sgpr GPR profile: step of acquisition is 26,03 mm.
Proportionality in distance - 1 m by vertical is equal to 1 m by horizontal

 
Pipe2.sgpr GPR profile: step of acquisition is 156,18 mm.
Proportionality in distance - 1 m by vertical is equal to 1 m by horizontal

We could suppose that using Migration method would lead to higher horizontal resolution.
But resulting images are the same:

 
The result of the migration for Pipe3.sgpr GPR profile (step of acquisition is 26,03 mm).
Proportionality in distance - 1 m by vertical is equal to 1 m by horizontal

 
The result of the migration for Pipe2.sgpr GPR profile (step of acquisition is 156,18 mm).
Proportionality in distance - 1 m by vertical is equal to 1 m by horizontal

It is clearly seen, especially for the object located at 2m depth, that the resolution is the same for the both profiles. At the same time the step of acquisition of Pipe2.sgpr profile is 6 times larger than Pipe3.sgpr profile (Pipe3.sgpr profile is six times wider than Pipe2.sgpr profile).
Increasing the step of acquisition six times allows you to increase six times the speed of the antenna movement without loss of horizontal resolution.