How is elevation of land measured

More accurate measurements are expected to pay big dividends. Scientists at the National Geodetic Survey are working on a year-long project to make accurate height measurement better, faster, and cheaper. When it is completed, you will be able to get accurate heights to within about an inch for most locations around the nation.

Not only will height measurements be more accurate, people will be able to more easily keep those measurements up-to-date and better predict how heights may change in the future. The improved model for measuring accurate heights will also be tied into GPS, so it will be easier and faster than ever to get accurate height information.

In low-lying coastal areas, accurate height information is critical for knowing how water will flow across the land for many applications, like monitoring levee heights, maintaining safe hurricane evacuation routes, creating more accurate floodplain maps, and managing coastal development as sea levels rise.

Accurate heights are also needed to maintain efficient water delivery and drainage systems and to help reduce urban and agricultural runoff and water pollution. While the aircraft flies back and forth in a grid pattern, a NGS scientist aboard uses scientific equipment to survey the geopotential for the entire state and surrounding coastal ocean.

The complex process of geodetic leveling that measures geopotential is a measurement of height times the change in gravity at a given point. Gravity has to be accounted for when taking elevation measurements because the Earth's gravity field varies from point to point. These variations affect how water flows. The grey lines are completed flights, while the red lines show where the plane has yet to fly.

According to my watch that claims to measure altitude, as far as I can see it says that in Stockholm Sweden the altitude is meters but can that be right?

How exactly can we know that 0 altitude in Bangladeh is the same as 0 altitude in Stockholm? Altimeters use barometric pressure to measure altitude or elevation. Your watch likely uses a Baro-Altimeter. The problem with that is that the barometric pressure also changes with the weather.

As the barometric pressure goes down your altimeter watch will think you are going up in altitude even though you are solidly on the ground. For such watch altimeters to work you need to calibrate the watch's altimeter on a daily basis or whenever you want it to be accurate. Then, as you travel around during that day your watch altimeter will remain somewhat close to correct as it senses the changes in pressure due to you changing altitude or elevation the ambient or "weather" barometric pressure will also change a bit throughout the day causing the watch altimeter to drift out of calibration during the day.

How do you know what your elevation is? You may need to reference a publication or map. If you are at home you can find out what the elevation of your home is through various means and calibrate using that. Some people even calculate the altitude of their night stand above the street level to get very accurate.

This is a hassle but that is the reality of using a barometric altimeter. You could also use a known barometric pressure setting for your part of town at the present time and set that in the watch altimeter as well if you can't figure out your exact elevation for a starting point. This is what we have to do as pilots. We either obtain the current barometric pressure and set the altimeter accordingly or at smaller airports we set the altimeter to the known elevation of the airfield we are at.

Pilots also have to continue to reset their altimeters during a flight as the barometric pressure changes through out the trip as you fly from one pressure gradient to another or as the local weather and pressures change. Nevertheless, there will always be some calibration error and inherent inaccuracies in measuring the altitude with your watch's barometric altimeter.

This is because sea level is not the same every where. It is rather complex. As explanation I show what wikipedia says about Vertical datum :. A vertical datum is used for measuring the elevations of points on the sea level. Vertical datums are either: tidal, based on sea levels; gravimetric, based on a geoid; or geodetic, based on the same ellipsoid models of the earth used for computing horizontal datums.

Whatever level you use, make sure you know what its length is for future calculations. A stack of bricks also work well to secure one side of the level. Adjust the other side of the level until it's centered. Start shifting the bubble portion of the level once the far side is secured into place.

Move the level slowly until it reads a level measurement. Measure the distance between the unsecured end of the level and the string. Use the tape measure to calculate the distance between the end of the level and the string. Depending on your land, this distance could be several inches or centimeters. Use the length of both your string and level to calculate the difference in elevation between your posts.

Take the total length of your string and divide it by the length of your level. Since this number equals the total difference in elevation from each post, multiply this number by the calculated distance between the string and level. If the distance between your posts is 2 in 5. Include your email address to get a message when this question is answered.

Invest in an altimeter to get an exact reading of your current elevation. While this technology is most commonly used in planes, there are also portable versions of the device that help with activities like skydiving. Helpful 0 Not Helpful 0. Additionally, you can plug a barometer reading into a specific formula to get a sense of your elevation on-the-go. If you want to survey an entire plot of land, consider hiring a professional team to do the job.

Submit a Tip All tip submissions are carefully reviewed before being published. Watch out for altitude sickness whenever you travel to a place with a higher elevation. Related wikiHows How to. How to. It measures 8, meters 29, feet. The Earth's lowest land elevation point is at the Dead Sea, located at the border of Israel and Jordan.

Its shores have an elevation of meters 1, feet below sea level. Sea level is determined by measurements taken over a year cycle. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

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