Best Way to Measure Elevation Profile of Land?

[walker450]

I have a 2 acre clearing that I would like to get a very accurate elevation profile of so I can model it in 3D. I will be using the free Google Sketchup program. I want to virtually build my house, shop, and driveway before I actually build it.

I want to do this myself to save money. I have done this on small scales by simply using very long hoses and making "water levels" and recording everything on a piece of paper. This was on areas big enough to build a shop on.

I have GPS on my iphone but I'm not sure if I could trust it to be accurate enough. I was thinking about taking elevation readings in a 20'x20' grid then entering them in the computer.

A laser level on a tripod would be great but I don't know anyone with one of those. Maybe I could do some searching and borrow or rent one.

Any advise would be greatly appreciated.

 

[BeezFun]

I'd rent a rotary laser. If you're really a spartan, you can tape a laser pointer to a 4' level and shoot grade at night. I've used water level for fairly large areas, but it's pretty flat here.

 

[Egon]

Get a hand level and a 1x3x8 ft. Piece of wood for a rod and you are all set.

(Kinda old fashioned but cheap and
It works)

 

[BHD]

could probably use Google earth, for a quick estimate

with these Colorado floods, my son was in the flood plane, and with the forecasts of the river crests, I used Google earth and estimated the flood waters and conclude it would be about 10 feet from there house, and the water came to with in 10 feet of there house,

and planed the exit rout via road ways and what roads would be under water first, for there evacuation orders,

it was very close.

 

[walker450]

Get a hand level and a 1x3x8 got piece of wood for a rod and you are all set.

I have done this before for small area... I would have to layout a grid first to make sure I'm measuring in straight lines. Whatever I do, I'll post results here.

 

[walker450]

could probably use Google earth, for a quick estimate

For some reason Google Earth shows large hills on my property that aren't there at all. However, I was very impressed with the accuracy on other land we were looking at before we bought our current piece.

 

[Egon]

I have done this before for small area... I would have to layout a grid first to make sure I'm measuring in straight lines. Whatever I do, I'll post results here.

Well, the grid you need anyway. And you surely know how to do it.

 

[forgeblast]

https://play.google.com/store/search?q=elevation&c=apps&hl=en is a list of different apps that might work if you have a smart phone.

 

[newbury]

What is the grid density you need for the critical items? What is the range of elevations? How big a house and driveway?

If you can get by with the approximately 200 points based on your 20'x20' grid that would seem cost effective and accurate. I don't know how you did it in the past but if you don't have GREAT variation a transparent tube attached to a PVC stake could give you great accuracy. And would be easy to densify with a smaller grid for critical areas.

 

[walker450]

My iphone "Trails" GPS app shows 30' of drop over 450'.

 

[JPRambo]

Does the county have a GIS (geographical information system) website?
I have a piece of land in Georgia and the county has a GIS site in the land tax website which shows the elevation in 10 foot intervals. Once I was able to get it to show me 2' intervals, but not since. Maybe someone in the tax office for the county can get it to print with elevations in 2' or so elevations.

 

[mikehaugen]

I would not trust an iphone gps for grading. As far as I know (unless it has changed) any consumer grade gps is only considered accurate to 3 meters for coordinates. I doubt altitude is any better.

As mentioned, it would be better to borrow/rent a laser.

 

[walker450]

I will check into the county info.

I have ruled out the iphone GPS. I walked the land in a grid pattern recording with an iphone GPS app. I then opened it in Google Earth and measured differences in intersecting points to check pass-to-pass accuracy. Many were over 10' off from each other. I would like to have +/- 6" height accuracy in a 20'x20' grid.

I am not going to be grading by these measurements. I only want to make a 3D model for me to mess around with.

Thanks for all of the comments and suggestions everyone!

 

[walker450]

Here is a screenshot from Google Earth. For some reason all waypoints were 1100' over actual elevation... so the track appeared to be a skyscraper lol. Hopefully you can see what I mean by the pass-to-pass inaccuracy.

 

[quicksandfarmer]

If it's 2 acres and 450 feet one way that means it's about 200 feet the other, assuming it's rectangular. With a measurement every 20 feet that's 23x10 measurements, or 230 total. If you spend 10 minutes on each measurement that's 38+ hours, or about a week. So the challenge is doing it in a reasonably efficient manner so it doesn't take you forever. There are really two parts to this. One is laying out a 20x20 grid with reasonable accuracy. The other is taking height measurements with reasonable accuracy.

Here's how I would do it, assuming the ground is reasonably clear, flat and free of obstructions. You can get a laser that will shoot the 200 foot direction. I would mark two corners along the 450' dimension. I would walk that line with a measuring wheel , and use a spray paint marking wand to put a dab of paint every 20 feet. Then I would do the same thing along the other 450' edge.

(One thing you'll have to ask yourself is how important it is to make a true rectangle at this point. If you don't want to just eyeball it, and you don't have any landmarks, once you've got your first two corners down you'll want to use a 3-4-5 triangle to find a right angle to them, and then use the measuring wheel and the laser to measure out two perpendicular sides of the same length, and then the laser to connect them.)

You'll need two laser target cards and two stakes, probably six feet or so. Use a ruler and a sharpie to turn one stake into a measuring stick. Put the target card on the other and pound it into one of your paint blobs. Put the laser on the matching blob on the other side of the lot and see if you can hit the target. Now walk from the laser to the target carrying the measuring stake, the other target, a notebook and pen, and measuring with the measuring wheel. (You'll need four hands!) Every 20 feet stop, get the target into the laser beam, and use the measuring stick to measure the height above ground. Record in the notebook. When you reach the other end move the stake to the next blob, move the laser to the next blob and repeat until finished.

A helper would be real handy, because otherwise you have to make a round trip for each pass to move both ends. With a helper you can do each pass in a single trip so you save half the walking. Even so it's about a mile of walking.

 

[farmer2009]

I would find a buddy or a rental center with a laser or at least a basic level the kind that takes two people and do your grid.

Might even check at Sears use to be able to buy one for around a couple hundred bucks. This would be my preference especially if you plan on doing the dirt work for your house other buildings yourself.

Just my 2 cents.

 

[buckeyefarmer]

a fairly inexpensive builders level and a rod.

 

[farmer2009]

a fairly inexpensive builders level and a rod.

Exactly what I was trying to think of.

 

[walker450]

Thanks farmer! You are correct on the approximate measurements, and it is mostly open. My next task is locating a laser...

I don't mind putting the time and effort into this. Once it is done I will have the info for the rest of my life.

Thanks everyone!

 

[bandaidmd]

A handheld locke level such as this and a helper with a 2x4 and a tape measure will also work.
You sight thru the telescope holding it level and measure whatever the height is on the helpers stick ( helper moves tape up and down stick until its level with yours)

CST/Berger Locke Hand Level - Hand Levels - Measuring Supplies - Supplies - Allen Precision Equipment