Re: Is there a way to look up how high you are above sea level on a map?

Dear Michelle:

Indeed, there is! If you know your Zip code, or address, or just plain where you are, then you can probably locate your home on a map or atlas.

There are many kinds of maps. Some show only the streets and buildings, while some include the vegetation and maybe even the location of electrical lines and other features. There is also a type of map known as a topographical map. The word "topography" is from the greek "topos", meaning "place". This kind of map will not only show you the roads and stuff, but the type of terrain that you have in the area depicted on the map, such as where the hills are, what kinds of vegetation there are, and so on. It is designed to give you an idea of the three-dimensional landscape on a two-dimensional piece of paper. This is especially useful for land surveyers, scouts, and hikers, who want to know what travelling in an area is like.

Now, on a map, you may find lines that seem to encircle hills and run alongside valleys. These are called contour lines, because they show the contours, or the outlines, of the landscape or terrain. If you look at a map with contour lines, like this one, you can see that there is a little number inserted in the middle of the line. This tells you that every point on the line (if you actually draw the contour line out on the ground) is at the same altitude (or elevation, that is, distance from sea level). So if you draw the contour lines on a map on the ground of the area shown on the map, and you walk along the line you've drawn on the ground, you'll be at the same altitude at all times.

Look at the following diagram:

       ___ ... 50m
     /_____\ ... 40m
    /________\ ... 30m
   /___________\ ... 20m
  /_____________\ ... 10m
 /________________\ ... 0m

Imagine that that shows a hill cut through the middle, and the numbers on the side are the altitudes of the horizontal lines that are drawn on the hill. You can imagine a hill, or any terrain, as being built up from a series of pancake-like layers, that just stack on top of each other, and each of these layers are of the same thickness. This is what is shown in the picture above. If you look at it from the top, those horizontal lines would basically show you the contours, because of you walk along these lines then you'll be at the same altitude at all points along it.

Now, closely spaced contour lines on a map mean that the place is a very steep slope (think about it...), while widely spaced ones mean that it is a gentle slope. If you have contour lines that converge on a spot, it could either be a hill or a hole in the ground, depending on which way they're sloping. The best way to learn about contour lines is to get out a map... and some plasticene (or modelling clay). It's messy, but fun! Use the clay to make landscapes (in the pancake style if you wish) and use a marker to draw out where you think the contour lines are by making sure that your lines are always at the same height from the table top. Alternatively, you can get a map with contour lines, and try to build up a landscape using modelling clay from there.

Okay, now to the meat of my answer (if you read my other answers you'll realise that I tend to take a long time to get to the point...). How to find your approximate height above sea level in six easy steps:

1. Find out where you are. The name of your town, your zip code, and so on
2. Find out where exactly that is on a map. You could try http://map.yahoo.com/
3. Get a good atlas or topographic map of the area you live in.
4. Locate where you are on the map.
5. Look for the contour lines around the place you are at.
6. Your height above sea level will be somewhere in between the heights of the two contours that surround the spot you have marked out.

Okay, so using contour lines isn't exact, but it's a pretty good way of getting a rough idea of how high you are above sea level. If you want to get a more accurate answer, you could try looking for a more accurate map of your area. Your local city hall or town planning authority might have more information that might be useful to you. You could even go to your local public library and ask the librarian to help you find people or maps that could help you. Get your parents to help you.

Finally, if you don't want to use a map at all, being fed up with contour lines (don't blame me! =P), then you could try obtaining a barometer. A barometer measures air pressure. The higher you go, the lower the air pressure gets because there's less air above your head that's pressing down on you. Therefore, you can use a barometer to measure quite accurately how high you are above sea level. There are many kinds of barometers so you'll just have to ask the person whom you got it from about how to use it. You could try asking your local high school or weather station for more information, and ask if they're willing to lend it to you. Of course, do seek your parents' help first.

Well, I hope my answer has been of help to you, and if you're still unclear, to write back to us mad scientists! We're alwasy willing to help. =)

Good luck! And happy mapping =)
Tan "Contoured" Thiam Hock

Some other resources you can have a look at:
http://ge ography.about.com/library/weekly/aa110298.htm
http://office.geog.uvic.ca/222- 2001/frLect12.html
http://maps.nrcan.gc. ca/maps101/links.html
h ttp://www.cchs.co.uk/subjects2/geography/resources/yr7contour.htm (colourful!)
http://nesen.unl.ed u/lessons/mapping/3dtopo.html (making a 3-d "topo" map)
And finally:
http://maps.yahoo.com/py/maps.py?BFCat=&Pyt=Tmap&newFL=Use+Address+ Below&ad dr=&csz=22003&Country=us&Get%A0Map=Get+Map
-- A road map (not topographical, though) of your neighbourhood