Measuring the height
that a plan and a map show smaller areas as seen from above;
that heights can be shown on the map by means of contours;
that there are relative and absolute heights.
determine the relative heights on the map;
determine relative heights in the field “roughly” and by measurement.
Measuring the height of a hill
The relative heightThe relative height can be measured in two ways. The first one requires the use of a contour map, i.e. one on which the contours are marked. To calculate the relative height of the hill you are interested in, first you have to find it on the map, then read the absolute heightthe absolute height of its top and subtract the absolute height of the hill foot from this value. In this way, the relative height of the hill is obtained.
The second way to determine the relative height is to measure it yourself. It is not difficult at all. All you need is a simple levelling instrument.
Determining the relative height of any hill.
school’s levelling instrument,
rocks,
string,
straight stick,
tape measure,
classmate’s help (measurement should be performed in pairs).
At the foot of the hill, drive the school’s levelling instrument in. Make sure that it is exactly upright.
Align the horizontal arm of the levelling instrument directly on the slope of the hill.
Turn the horizontal arm of the levelling instrument towards the hill, point it to the left of the slope, and then ask your friend to mark the place you are aiming at with a rock.
Mark the position on the right side of the hill in the same way by turning the horizontal arm of the levelling instrument slightly to the right. Then mark a few points between them.
Use string to connect the areas marked with the levelling instrument.
Move the levelling instrument to the place marked with the rock. Repeat the previous steps creating another contours.
The last one that requires measurement of the height can be smaller than 1 m, and if this is the case, place a straight stick on top of the hill. Aim the levelling instrument at the stick and ask the classmate to mark the point on the stick you are aiming at.
Use the tape to measure the length of the stick from the top of the hill to the mark and subtract the measurement result from 1 meter. You will get the height from the last contour to the top of the hill.
When you add all the results, you get the sum of the measurements, i.e. the relative height of the hill from its foot to its top.
You can determine the relative height of the hill and the contours with simple instruments. Make sure the levelling instrument is correctly set – otherwise the measurement will be erroneous.
How to measure the height in the field
Now let's assume that we want to determine the relative height of a tree or a building. We will not find it in the maps. If we look at a modern building, we can assume that its floor is about 3 meters high. For example, a four‑storey building with a ground floor is about 15 m high. If we want to know the height of a tree growing in a city, we can compare it to a house standing next to it. What if there is no house nearby? On a sunny day, you can easily calculate the height of any high element in the field from the shadow.
Measuring the height of the church tower in relation to the land surface.
tape measure.
Measurement should be performed on a sunny day.
Measure the length of your shadow with the tape measure.
Measure the shadow length of the church tower.
Calculate how many times your shadow is shorter than that of the tower. For example, if the length is
Multiply the result by your height. If you are e.g. 140 cm tall, then 20 x 140 cm = 2800 cm = 28 m
You do not need to climb the tower to measure its relative height. However, shadow measurement may be inaccurate.
On this day, the shadow of the 2 m tall basketball player was 4 m long, while the shadow cast by the Eiffel Tower was 648 m long. What is the height of the Eiffel Tower? Choose the correct answer.
- 162 m
- 324 m
- 648 m
- 972 m
Summary
Heights can be measured in the field with a simple instrument – a levelling instrument.
The height of some objects, such as trees, can be measured “roughly” by the length of the shadow they cast.
Keywords
contour, relative height, absolute height
Glossary
wysokość bezwzględna – wysokość mierzona od poziomu morza; wynik odczytuje się bezpośrednio z mapy (bez obliczeń) i podaje się go w metrach nad poziomem morza (w skrócie: m n.p.m.)
wysokość względna – wysokość mierzona z dowolnego miejsca, np. od podnóża wzniesienia do jego wierzchołka