IMO you need two things to get started, a wind gauge and a few feet of surveyors streamer tape.
Hang the streamer tape near the gauge and observe how much wind it takes to lift the tape to (approx) 20deg - 30deg - 45deg. It is also helpful to see how the wind effects the vegetation in the area.
It will take awhile but eventually you will be able to judge the wind speed by the angle of the streamer tape and the wind effect on the vegetation.
If it is at all possible, put a streamer down near the anticipated shot location. If not, watch the grass, leaves or whatever else is around to help you judge the wind.
Judging wind over long range is difficult because even if you have accurately determined the wind speed and angle from your position, it could be quite different down by the target or anywhere in between. The wind often blows in gusts and abates in between, or it may switch directions entirely, going in one direction at the target and another where you are standing. You must take these variables into account if they are present.
Naturally, you will need to know how the wind effects your particular bullet and at the muzzle velocity it is going from your rifle. A ballistic chart or loading manual will usually provide you with this info.
It is also VERY helpful if you shoot a high BC bullet. This will reduce overall wind deflection and minimize your errors.
Hope this gets you started. Figuring out the wind over a long distance is much harder than determining bullet drop over the same distance. Bullet drop is basically a known factor.
VH
