Re: Terrain and Wind
RickP - in SW OR, the only areas I have available to shoot long are steep mountainous areas. A typical shot for me is across a narrow, steep draw.
Here are some thoughts:
- You can not read it in a book or watch it on a video - you actually have to go out there and sling lead. Formulas don't get it done, you really need to develop a sense for it.
Things that flatten the learning curve:
- Think of wind as water. If you look at a stream and watch the water flowing you will note that the effect of the current varies with the grade, depth, and the width of the stream bed (getting at the concept of recognizing what land formations lend themselves to velocity changes). Along the same line of thought, consider that if you send a volume of water down a 10" pipe, then step it down to an 8", then 6", then 4" and finally a 2" pipe - your increasing the pressure on that same volume of water with each reduction in pipe size. (Same thought if a wind flows up a broad valley and through a series of progressively more narrow formations.) Back to water - sometimes current flows over or around rocks, and sometimes it eddys or swirls back. If you watch that same riffle / rapid throughout a range of flow rates - you will notice that at some flow rates it merely flows over or around, while at other flow rates it eddys, and some times it not only eddys - it whirlpools. Same deal with land formations.
- Have a topo map (know how to read it and be able to recognize distinct land formations which are represented on the map with a quick scan -
GPS Land Navigation by Ferguson has a section in the back which does a nice job of explaining this - if you need it).
- Understand seasonal prevailing wind patterns for the area - what direction are they generally coming from, what speed, how do things typically flow during the day, how does that change with the season or time of year?
- When you're on site, and thinking about the seasonal winds, reference the map and scan the area. Depending on the number and severity of topo changes in proximity to both the shooting position and the target location, you may want to start thinking about the cumulative effects on the wind at your target area that are generated by the topo formations that are 1, 2, maybe even 5 miles away.
- Watch for wind eddys - say your target is near the top of a draw, as the draw comes to it's vertical end, if it is steep it will have compounding effect on the wind speed. If the target is not on the crest and the wind speed is sufficient - you can see an eddy.
- Listen to the wind on site. If the weather is constant you will note that the wind is running more or less on a cycle. If you pay attention you can identify the change based on not just observable but audible conditions.
- About the only 'formula' work you can do (given the above already) is to take your spotter and use it to see if you can observe vegetation / foliage or mirage at each of the following locations - nearest any land formation that may have an impact on the wind at the target, 1/2 & 3/4s of the way to the target, the target itself. You can run the standard formulas based on these observations, but in time you will come to see that they belie the truth; and the truth is you really just need to be able to sense it, b/c there is as much art as there is science to it.
Good luck
