# Measuring height difference over 200 meters without clear line of sight?

I recently got access to a piece of land including a spring and a pond. Since the terrain is slightly sloping after the pond´s drain, I thought on using the water flow to power a small hydro station.

Without having to consult some people from surveying and mapping or use their equipment I want to roughly guess the height difference between the pond´s water level and the intended location of the hydro station.

Horizontally the hydro station will be about 200 meters downstream, and there is no clear line of sight between the pond and the hydro station´s location due to trees and certain terrain features.

How to best make a rough guess (+- 2 meters) at the height difference? (I estimate it to be somewhere between 10 to 25 meters.)

• Have you tried doing it in segments? Oct 12, 2014 at 11:54
• Doing it in segments came to mind, maybe using a piece of wood and a level, but that takes quite long if the plank is only four meters long. I will keep that as last resort however. Oct 12, 2014 at 12:54
• No, use a laser level. Simple, fast, and super accurate. Oct 12, 2014 at 13:43
• I just took another look at the location, I might be able to enhance line of sight by cutting back some branches. What is the usable lenght of the laser beam of the laser level? Oct 12, 2014 at 14:03
• Night, or day? Which laser level? Oct 12, 2014 at 14:13

If you are moderately careful you can do it by eye with a regular level. If you happen to have a laser level easily available, you can use that, it's easier. In either case, the method is the same - pick your starting point, and set the level on a stick (or tripod) above it. Measure the distance from the ground to the level, write it down, then use your eye on the level or the laser to mark a spot on the ground that is at the same height as the level. Go to that spot and repeat. Add up all the "height above ground" measurements and there is your rough estimate. This is (almost, but not quite) the same procedure that has been used by surveyors (with "better than average" care and tools) for centuries up until the recent introduction of "total stations" which allow them to get away with faster methods these days (and make "merely old" surveying equipment quite cheap, at least until it passes into the "expensive antique" era.)

If you actually have a rise of 10 meters in 200 meters, you won't need much range on your laser, as your "average" distance in that case would be ~40 meters or so (if you were as high as 2 meters off the ground - 1.5 meters is often more comfortable to work with unless you are very tall.) Working on an overcast day or in the early morning/late evening also increases the effective range of a laser over what you can spot in bright sunlight. One way to cheat is to use a white card and walk away from the laser holding the card in the beam - you can often see the beam that way when you cannot simply pick it out amid trees and foliage.

Edit: per comment on @Peter's answer, an example of a google earth elevation profile (complete with mythical cliff) - this may be the quickest method, if not of stunning accuracy:

• I was still working out the procedure, but this seems like the solution. So thank you for that. Oct 12, 2014 at 18:23
• Good answer - This method works well. I did this by mounting a sight on a 2"x2" stake, about 6' tall at a height comfortable for me (~5'6"). I attached a corner level on the stake, plumbed up the stake, looked down the sight board and had my helper put their foot where it the sight hit the ground. I started at the low spot and worked up the property. Repeated moved my stake to the helper's food location and soon I had my answer. Elevation change roughly equals number of measurements X the height of my stake's sight. Certainly close enough for this kind of work. Oct 13, 2014 at 19:15

The solution is almost certainly in your pocket in the form of your smartphone. Perhaps it has a GPS that will tell you the exact elevation of both points. If not, install some sort of exercise tracker (designed for runners and bike riders) and start your "run" at one point, then get to the other somehow and end your "run" - the app should then tell you your net elevation gain or loss.

I used the GPS approach to work out some information about the height of a ridge that might have interfered with an antenna and it worked beautifully. But not all phones make it simple to get this information, so use an app to help you if need be.

• I like the idea, Kate, of using technology if it works well. The iPhone 6 has the barometer - and perhaps other phones do too, I don't know offhand - and one could certainly employ that to determine the elevation difference, probably within a couple of meters of accuracy. Oct 16, 2014 at 13:32
• I don't think I'd trust the accuracy of that. GPS is at best accurate to 3m - which I certainly wouldn't be very happy with! Nov 13, 2014 at 14:51
• Accuracy is different to precision, and for height differences, the precision of GPS is much better. Newer GPS are also better: they can use more different satellites, so adding precision. Just: check position of satellites (scattered is a lot better [DOP parameter]), not windy (on high level, check the clouds), and both measures within short time with same device (15 min) would improve data (either accuracy and precision). Oct 26, 2017 at 11:33

I think in your circumstance I'd either invest in decent laser level as per Ecnerwal's answer. Or perhaps more cheaply and also perhaps more accurately (debate!) I would buy or make a simple water-level. If you're not familiar with this then basically it's a tube - which is clear at least in part to allow you to see the water level within.

Water will always find a true level, the laws of physics dictate that. You could make one quite easily with a length (or two or three) of hose - and a couple of pieces of clear pipe stuck on the end. Lay the hose from one point to the other, clear tubes uprightish. Fill with water (perhaps pre-fill with water will be easier in your case). The water level you can see in one clear tube is the same as the water level you see in the other.Drive a stake in the ground to the water level shown. Hey presto, the tops of those stakes are bang level and you can do your working from that.

As a precaution, ensure that both clear tubes are reading the same level when next to each other. If not, there may be bubbles in the line. If they read the same level then you are good to go and can just walk to the other end.

Get a friend with an iPhone 6 (or an Android phone with barometer). You should be able to get within 2 meters accuracy if you measure the pressure at point A, then compare it (as soon as possible) to the pressure at point B. You can then go back to point A and see if it has wandered at all. If you do it within a few minutes, you should be able to get better than 1 meter accuracy.

• I don't see how this will help the OP with his particular situation. He isn't looking for pressure, and using pressure will be a very inaccurate solution, as compared with other methods that have been brought up here. Oct 14, 2014 at 23:09
• @J.Musser over a short time horizon, using a barometer to measure pressure can give you accurate height readings. This is how aircraft measure altitude. The iPhone 6 sensor can easily give you sub-foot differential height accuracy. Oct 15, 2014 at 21:04
• I don't know how good the present generation of them are - early "digital" barometers were fairly terrible (and the same can be said for most digital compasses, as opposed to GPS) but if they are now reasonably accurate this is a valid method over a short time horizon. Does remind me of the old joke about measuring the height of a building with a barometer, though; the joke was anything but measuring the pressure differential; drop it and time the fall, measure its shadow and the building's shadow, & ending up with offering the janitor "this nice barometer" to tell you how tall it is. Oct 16, 2014 at 2:39
• And many phones that don't have a barometer do have GPS, so you could measure it that way, of course. Google earth is another "out in left field" method that can work, if their elevation data is not too messed up (they have some mythical cliffs representing glitches in their data near my house, at least, but you can put in a path and get an elevation profile from it.) Oct 16, 2014 at 2:43
• My current electronic barometer is good down to 0.1 hPa. On a calm day, that should get you to within a few meters of your altitude difference: mide.com/products/slamstick/… Oct 16, 2014 at 13:41

Just use clear tube. Put some water and see the level of water on the both side.

• Could you explain more how you would do it? 200 meters long tube is also not so practical. Oct 26, 2017 at 11:22
• Really? it not only distance that is problematic, but height deifference. And how to keep 10 to 25 meter tube vertically, from the ground? Nov 7, 2017 at 15:11