Measuring my altitude above sea level accurately

Question

I live in a building which sits very high near the top of a hill. I estimate the ground level of the building to be around 700 feet, I live on the 13th floor, so my altitude is approximately 800 ~ 850 feet. I would like to get an accurate measurement (correct to +- 10 feet).

How I did the measure

• Measure the ground level altitude at a park with a phone GPS
• estimate the height of each floor
• I have a laser measurement tool which I can use to measure my ceiling height. But the height of each floor is ceiling height + some concrete. My tool cannot measure the distance from ground to my floor, it's too far away.

Other considerations

• Using a GPS unit in the flat would produce inaccurate results
• GPS units are inheritly inaccurate at altitude (compared to lateral position)
• I cannot access other floors other than the one I live
• I have a good view of the city. By looking at a map, I can accurately calculate my ground-level distance to certain sea-level landmarks. These landmarks are some 5 km away.
• I would like to minimize the cost of purchasing special equipment.

Answer 1

The first two ideas require knowing the altitude of your building.

You may have a building manager / contractor that actually knows how tall each story in the building is.

Tie a rock to the end of a string, hang it out your window, and measure how long it is when it touches the ground ( think "kite string" )

Other than that I think you will need rather precise tools to get a better estimate than just guessing at the height of each floor.

Water boils at different temperatures at different altitudes, but we're talking about a few degrees at most. So, you're going to be needing to be able to measure within thousands of a degree to get within 10 feet.

It is simple to make a clinometer, fir which you can measure the angle to an object of known distance. I believe tan ( angle ) / distance will give you the height difference ( trigonometry ). Again though, the further away the object, the more precise you will need to be. If you knew the altitude of your building, you could even measure the angle to across the street.

Answer 2

Some of the more modern smartphones (especially flagships) have a barometer integrated to assist with the GPS altitude measurements. So technically you could use your phone's GPS to determine the altitude (bear in mind to stay close to the window, possibly even open the window for a better GPS signal).

An option is also, that you put a marker of some sort on your window, that measures exactly 1 foot, then take a photo of your building, where you can see your window and the base of the building simultaneously, without using special (fish-eye) lenses, then you can use pixels as a measurement of approximately how high you are living.

Answer 3

Shadow measuring.

This isn't always possible, but it should be at midday in most places.

The stick is 1m tall. You measure the shadow and it is 0.3m tall.

You then measure the Building's shadow. It is 10m.

We can use "similar triangles" to work it out.

1/0.3 = 3.33...

10 x 3.33... = 33.33...

So the building is 33 m tall.

Here is the formula:

Stick Height
------------  x  Building Shadow = Building Height
Stick Shadow

Answer 4

Stand on ground next to wall and measure the distance straight up to the 1st floor. Use string or a tape-measure if it reaches. Or use your laser. Then multiply by 13 and add to sea level at ground.

(x * 13) + 700

Answer 5

Flip the building horizontal

I'm presuming the ground height of your building, 700 feet, is good enough for your purposes, so it's really a question of finding the height of your building. If not use a local typographic map with height indications.

From a viewpoint where you see both the base and your floor of the building, use some measure to rotate the height of the building into a horizontal distance. I.e find something which at an arms length equals the height of the building, and then rotate this length to the horizontal level and measures it afterwards. This does require free sight to a point horizontal to the left or right of the base of the building...

Edit: Here are some illustrations of the concept.

Stand sideways at point where you see the entire building. At an arms length hold a stick and make the top align with the top of the building, and put your thumb at the point aligning with the bottom of the building. Now rotate your arm 90 degrees.

Now align the thumb to the corner of the building, and mark out where the top of the stick is pointing. Go over to the building, and measure from this poing back to the corner of the building, and you have the correct height of the building.

Essentially you flipped the building from vertical to horizontal, and are now able to measure it more easily.

Major edit: Hopefully this is not so vague, and illustrates my point of flipping the building over much better. Images made by myself

Answer 6

The angular approach

Either from the flat or from the outside find a point at the same height as the base of the building, and use some device to calculate the viewing angle to the point. Measure the distance at base level to your point and use standard calculus to find the height (I.e use Pythagoras therom)

If you have 45 degrees, then the distance from the building is the same as the height. Add this to the known height of base level of building.

This method requires the most calculations, but could be the most precise given that you are able to get a good reading of the angles. See also measuring the height of trees from StackExchange, or tree facts from OneOak regarding the formulas.

The formula to use is:

Height of building = ( tan a * AB) + (tan b * AB)

To get the angles, either use a hypsometer, like the one in the OneOak link, or try something like the following:

• Hold a piece of board to a wall and get the proper sight of the top (or bottom) of the building along the edge of the board
• Put your smart phone on top of the board
• Use a bubble level app to read out the angle of the board

Major edit: Keeping the concept, but adding illustrations and references to another question on StackExchange, which refers to the same methods as I've presented here (amongst others)

Answer 7

Easy,

1. get the height between ground level and your eye (suppose you got 6 feet).

2. hold a torch or any light source on your head as shown.

3. stay away 40 feet from the building.

4. see the building as mid eye sight.

5. get the distance between you and light reflection on the ground and reduce 6" (distance of torch and your eye)( suppose you got 2 feet)

6. do the simple calculation. -> (6/2)*(40+2) = 126 feet high building.

Answer 8

Measure level height

From your window use your laser measuring device and measure the distance up or down one story, and multiply by your level. Measure from bottom to bottom of the window, of from top to top.

The key point is to measure two known distances (A and B) with your measuring device, subtract these from each other, and then you get the exact height of each level. Multiply and add this to the known height of base level of building.

In this way you don't need access to the other levels, except for visual references. But you are still able to get a fairly accurate height between levels/floors.

Edit: Edited as someone downvoted solution, without grasping the context, which is doable and usable.