When I SL mortars I move my attack marker back and forward to get the exact range.
For instance, I first mark the position I want to hit. I then move the marker further away to see how accurate the distance is. If it takes a while to increase the range indicator by 50m then I know the original distance is accurate. If on the first move of the marker the range increases by 50m then I know the original distance is less accurate and I adjust the range to be closer to the extra 50m increment.
After a very short while of doing this you can get a feel of whether to increase or decrease your range by 10-50 metres.
P.S. To OP: No information is useless. When you first receive information it might appear pointless, but in time it may prove useful

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Extra info:
Logi truck repair stations rearm in the field automatically. You don't have to RTB to rearm them. I've come across a surprising amount of people who don't know this.
In AAS your team loses 30 tickets if the enemy captures your flag.
On INS the first cache is revealed after a certain amount of time. This means you can spend the time strong pointing cities without losing unnecessary tickets by entering densely populated areas at the start of the game. Use this time to set up a strong logistics network blufor.
If you have trouble building fobs or emplacements on hill sides try to look up the hill or lie prone parallel to the place you want to set it. Looking down from higher points is rarely successful.
Don't fire tank AP shells on the canvas part of logi trucks. It often does no damage to the vehicle.
All munitions and supplies are rearmed quicker from the small ammo crates and ammo bags. The big crates and half crates rearm you much slower, in spite of having a larger quantity of supplies.
If you become wounded (without becoming dead-dead) you still cost your team 1 ticket. If you go straight to dead-dead you lose 1 ticket. If you become wounded then become dead-dead you lose 2 tickets (one for each stage).
APC AP rounds can kill infantry, but have no splash damage. And yes, I have been in situations where I've had to resort to using them to kill HATs

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