To make sure that I understand the initial example, and that if range is not stretched far beyond 700/800 yards the use of Field Charts is very appropiate as long as atmospheric standard conditions are used, if we only know altitude.

Here goes an example, where the shooter can interpolate the middle values for the incline angle, just to obtain a sensible, good prediction for a first shot.

Of course, Field Charts are handy, since they never run out of batteries, are imprevious to rain and sun, and they cost nothing!

First the values I used :

Second the complete results

and finally a Field Chart, that in this case calls for a rapid interpolation in order to find an approximate value for an incline of 25°