Thread: using GPS as a rangefinder

You CAN use GPS or phone (Balistic app with maps etc) as a rangefinder when you are in a low drop zone, ie probably 100-200m. After that the inaccuracies will most likely mean a miss for you.
As previously stated, if your accuracy is +-10m and your pinpoint is +-20m (which is hard to determine exactly unless you have significantly good terrain markers), and you are say 150m range (which you do not know exactly), you have an uncertainty of 150m +-30m, so anything between 120m and 180m.
If you shoot a 180gr 308 projectile, your drop between the 120 and 180m may be roughly 285-123=162mm. Still good enough to hit - maybe just about.
If we do the same calculation for say a distance of 200m (so a range of error between 170m and 230m), your drop will be 478-253=225mm between the two distances. A chance for a miss.
And now we add any angles to it ie down or up and it get a wee bit more complex. The further you go, the worse the error drop gets and the more important range accuracy gets.

So my take on this thing:
For 100m you do not need a rangefinder or GPS. You shoot, you hit - if your rifle is sighted in to 100m or hold a tad under if zeroed to 200m.
For 200m your GPS may be handy but you could also do a shoot and most likely hit if your rifle is zeroed to 200m.
For 300m and over the accuracy will not be enough.

All the above will depend on your zeroing, your caliber and the projectiles you are shooting.

I shoot Rimfire at ~200m and GPS is way, way to inaccurate. the drop difference at even 5m is massive (~90mm per 5m)

so lets do the same with some real world figures and the mighty 270
figures rounded for ease...
3" high at 100
dead on at 270 yards
6" low at 350
backbone hold at 400
your 180grn 308 is awesome bush load but not really an easy longer range option.