Line-of-sight measuring

[MissJean]

Here in Nashua, the Con Comm rules state that nothing can be put within the 40' buffer zone around prime wetlands. That is 40' line of sight, as the crow flies. 41' you're golden, 39', you have to go to a bazillon meetings and get permission.
Well, on the trail I've laid out there is a spot that is as sweet as sweet potato pie, it goes down along side a rocky outcropping, with a couple of trees set just so, so you'll have to tweek the bars to get through. :D I've GPS'ed it and it comes up 38'. >:( I know there is a +/- of a few feet with GPS-ing, so there is hope.
My question is what other method can I use to get an accurate measument? Stretching rope won't work because the wetlands is a good 15/20' drop down the slope, so I'd never be able to get the far end of the rope up to the trail level.
Any ideas would be appreciated.
Jean

Tie one end of the rope at trail level, weight the other end and throw it down the slope to the wetland edge, go down to the wetland edge, pull the rope taught, make a mark then go back up, pull up the rope and measure? Thought about range finders (used a lot in golfing) but good ones are expensive and prob. no accurate enough for that small a distance...Bob

You will need a friend to help but heres a way.

You need a plumb bob and a string level. Stand at the begining of the measurement area. Hold the plumb bob vertically over the start point and have you friend run the string out horizontally till it runs into the rising slope. Use the string level to make sure you run the string out level. Mark the point on the ground where the level line hits. Measure the horizontal distance between the two level ends of the string. The next measurement begins where the last one ended. Add all the measurements up and you have your distance.

Imagine that you are creating a staircase up the slope and just measuring the steps, not the risers. This method will also work if you want to determine the elevation change. Just add all the vertical measurments.

an old boy scout
bill

if you are looking for the "level" horozontal distance from the trail above to the edge of the "water, you can still use the "rope measurment "down" the slope in conjuntion with an angle measurment taken with an inclinometer from the trail level looking down to the wetland edge. With the "rope distance" and the angle of slope you can use Trig. to calculate the horz. distance from the trail to the wetland. (b = a X cosine of C) b=horz. distance you are looking for.....a="rope measurment down the slope to the wetland edge.....Cosine C=cosine of angle of slope from trail to edge of wetland(get from trig table. math book or a nut like myself) Angle measurment should be accurate to a degree or two and you will be well within a foot of what you need...Bob

[MissJean]

Thanks guys! I knew there had to be another way to measure.
Keep your fingers crossed that it comes out 40' +

[Kenquig]

As an engineer and a former concom member I would accept nothing but a surveyor's survey to prove that something is 40' and not 38'. However, is someone really watching that closely that it is an issue?

Ken

[MissJean]

For brevity's sake, I didn't give the back story, but this is the first offical SC NH nemba chapter trail to be cut in Nashua, and I want to cross all my T s and dot all my I s and keep everything above board. Better safe than sorry. There is a whirl wind of political crap blowing around the Parks Dept lately and I want to make sure we stay out of it.

[Kenquig]

If it is that political and that close a surveyor would be the way to go. Of course you may spend the money for a surveyor and still come up within 40 feet.

What type of a wetland is it and how do you know you are measuring to the edge of the wetland? I know the Mass regulations pretty well (but and not up to date). I do not know the NH regulations at all. If I can be of any help email me.

My bet is that you are within 40 feet and it would be safest to be clearly beyond 40 feet.

Ken

[dsi]

You may find it educational to bring a tape measure into the woods with you. Locate both ends of the tape with your gps. Move the tape to a different location and repeat. Then inverse between the gps locations and compare with the tape length. It is unlikely you have a gps unit that provides differentially corrected positions real time since those cost around $10K. Money much better spent on bikes and gear. Assuming the limits of the prime wetlands have been accurately locate on the ground by a qualified soils scientist. Doubt it. First rule in surveying is measure from the right point. Buffers or setbacks are measured on a horizontal plane. So you need to raise the low end (prime wetland side) of your tape to a height nearly level with the upland then add 25 feet to the min. dist. to be safe. The State of NH has some pretty stiff regulation on Prime Wetlands that may exceed the local regulations. I know you don't want to hear it, but maybe this is one area you should stay away from.

[knucklebuste]

Whats the problem here? I ride through the wetlands all the time and I've never had to go to a meeting?
???
Knuckle

[Kenquig]

I go along with DSI. I was going to ask what you meant by line of sight measuring. The measurement should be on a horizontal plane. Unfortunately I also agree with dsi's assesment to stay away from this area if it is a political issue.

[MissJean]

Well, I went down to the site this weekend with a couple of the Con Com folks. We climbed up and down and all around, looking at the plants & water & dirt and came to the conclusion that the line between wet and non-wet is a bit further out that I had hoped. So it does fall inside the 40'. Fooey :(
There is a nice line a bit further up the hill, I guess we'll just stick to that.
This is what might have been. Under the leaves it is rocks. The approach was from the left, down, then curve up around the tree to the right, then through tree 1 & 2. Tree 1 is set a bit back from tree 2. At the base, they are about 10" apart and angle out to about 23" at handle bar height, so you have to tweek your way through. Then it drops down over more rocks, and you zip out up and to the right.

[MissJean]

And here is the exit. It looks like you could go further to the left, but it starts to drop. You can't really see it from this picture.