How to measure the gradient/height differen of a long slope?

[Frimley111R]

We are putting in a long zip wire system for a customer and need to calculate the gradient of the slope. What I think we need is some type of GPS device that allows us to stand at to the top of the filed and the bottom of the field and show us the height difference, we can do the rest. So, where do I get one (will a smatphone do it?)

[Munter]

I think what you really need is a Theodolite. And I think there might be an app for that...but how good it/they are I have no idea.

[16v stretch]

Just use a protractor. No need to go gung-ho (unfortunately)

http://www.lakeway-tx.gov/DocumentCenter/Home/View...

eta: Basically the same principle as a theodolite, but costs about 50p from WHSmiths.

Edited by 16v stretch on Friday 12th June 16:53

[Crusoe]

take a photo from the side, measure something in the photo so you know the scale and then you can measure the difference between the two objects.

[jeremyc]

A GPS receiver will not provide the necessary accuracy for accurate altitude measurement (whether in a standalone unit or a smnartphone with app). The error in elevation can be up to 45m.

Why not find some good old maps of the area and work it out from the accurate surveys provided by cartographers.

[tendown]

Depending on the distance/height you could buy some cheap clear pipe, fill with water and food dye, and check levels at each end. This would be exact and minimal outlay.

[B17NNS]

Water level.

[Muncher]

tendown said:

Depending on the distance/height you could buy some cheap clear pipe, fill with water and food dye, and check levels at each end. This would be exact and minimal outlay.

That, or do what I do and use a laser level once it is a bit dark.

Edited by Muncher on Friday 12th June 18:00

[Condi]

jeremyc said:

A GPS receiver will not provide the necessary accuracy for accurate altitude measurement (whether in a standalone unit or a smnartphone with app). The error in elevation can be up to 45m.

Of course it will. Probably not on a smartphone, but you can use RTK systems which have a basestation and correction signal to measure very accurately. How do you think they get roads graded these days? Bulldozers etc have GPS units on the blade and work from that.

[wolfracesonic]

What sort of length and height difference, roughly, are you dealing with? Maybe hire an optical level and graduated surveying staff. They'll give the height difference, then a tape measure and a bit of geometry will give you the gradient.

[Paul Drawmer]

Look at the location of the top and bottom of the slope using Google earth. The info bar at the bottom of the screen shows the ground height at the pointer. subtract one from the other to get the total elevation change of the zip wire. Using Google earth, you can set it to measure distance. You will be measuring the horizontal distance. Use trig functions in excel or similar to give you the angle and length of wire.

[Simpo Two]

16v stretch said:

Just use a protractor. No need to go gung-ho (unfortunately)

http://www.lakeway-tx.gov/DocumentCenter/Home/View...

eta: Basically the same principle as a theodolite, but costs about 50p from WHSmiths.

I made a big one of those to measure tree height for O-Level biology!

[otherman]

What sort of height roughly, a few meters or maybe 25 or 50? How accurately do you need to know? A land surveyor can use a theodolite and get you an answer to a few mm, but there are various ways to estimate if depending on how accurate you need the answer.

[TheInternet]

Can't believe some of the answers given so far. Depressing.

[Simpo Two]

TheInternet said:

Can't believe some of the answers given so far. Depressing.

Only if he's at the top of the slope...

[RichB]

TheInternet said:

Can't believe some of the answers given so far. Depressing.

And your answer is what?

[Paul Drawmer]

Frimley111R said:

We are putting in a long zip wire system for a customer and need to calculate the gradient of the slope. What I think we need is some type of GPS device that allows us to stand at to the top of the filed and the bottom of the field and show us the height difference, we can do the rest. So, where do I get one (will a smatphone do it?)

This intrigued me. How did you do it in the end?

[paul.deitch]

jeremyc said:

A GPS receiver will not provide the necessary accuracy for accurate altitude measurement (whether in a standalone unit or a smnartphone with app). The error in elevation can be up to 45m.

Why not find some good old maps of the area and work it out from the accurate surveys provided by cartographers.

It could but it will cost you about 20k to purchase.

[singlecoil]

Have a look at the Leica Disto

http://www.laser-measure.co.uk/leica-disto/leica-d...

[T.J.B]

IMO best way with regards to accuracy and cost would be to hire an automatic ("dumpy") level and staff. Maybe £30 tops for a week.

Level difference would be accurate to sub centimetre and then you can use Stadia Tacheometry for the distance.

A survey grade GPS (pedant GNSS!) will give you 3D positions to circa 20mm. But cost wise is around £400 for a weeks hire