Yes, they have inertial guidance. You do not need mechanical gyros for inertial guidance. You use electronic ones==
Electronic gyro? Let them use them. They are very inaccurate.
A German test of the smart fuse which is added to conventional 155mm artillery shells found, at 27 km, 90% of the smart fuse shells hit within 5m of their target. That was in 2014.==
It is GPS guided. It can be if GPS is not jammed. But all real material depos at this war always defended by AA machines and GPS jammers.
Most of the correction to the trajectory occurs before apogee of the flight of the projectile, ==
Why to correct at this stage? You kind of defeat a purpose. During flight there can be like atmospheric turbulence which drag away projectile and you are not correcting it anymore.
Russian shell is corrected just when it goes down on target so they are more precise then.
Not a bad system, but, unfortunately, with GPS already there, very little commercial market for Glonass. This limits the incentives for continual improvements.==
How GPS may get a commercial returns if it is just broadcasting system for anyone to listen? I doubt that GPS got any penny from Russia for example but we use it for years.
But Glonass is embedded to any weapon system Russia sells. SO any country say from Afrika may have a cheap high precision weaponry with satellite targeting. SO it is a commercial returns.
As I have written, repeatedly: Smart munitions do not need laser guidance. It can be used with many. It can drop the error from 5 meters to .5 meters. But with an artillery shell, 5 meters is almost always enough.===
If you need to hit up say one blindage or one tank or one ICV which you see from your drone then you will very need 0.5m precision. Russia uses them today exactly this way. To take out a blindage or a tank or a group of soldiers and so on. 5m is too much for such targets to destroy tank or blindage if it is just 10-20 pounds of explosive but just shake it and scratch it.
It might take two or three smart munitions to kill one.
A hit a meter away will disable one, at minimum.
Then there are the loitering munitions which deploy above tanks, and pick out the tank to hit, all internally programed. Multiple munitions from one shell. Takes out 2 tanks with one munition each, through the top.
You may believe differently, at your peril, but that is your choice.
One possibility is the system learns what is going on in the atmosphere on the way up, and applies those corrections on the way down by memory.
Atmospherics are very important, but are most important in the first two thirds of the flight. They are least important at the termination of the flight.