TERM – 2^{ND} TERM
WEEEK SIX
Class: Senior Secondary School 3
Age: 17 years
Duration: 40 minutes of 5 periods each
Date:
Subject: Geography
Topic: MAP READING
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,
demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures
INSTRUCTIONAL PROCEDURES
PERIOD 1-2
PRESENTATION |
TEACHER’S ACTIVITY |
STUDENT’S ACTIVITY |
STEP 1 INTRODUCTION |
The teacher introduces gradients and vertical exaggeration and give formulas for calculating them. Teacher aid students to carry out calculations |
Students in small groups calculate the gradients and vertical exaggeration. |
STEP 2 EXPLANATION |
Teacher discusses the procedures for drawing cross section /profile; |
Students in group describe the procedures for drawing cross section/profile |
STEP 3 DEMONSTRATIO N |
Teacher show students how to interpret cross section/profile to determine indivisibility of places on topographical maps |
Individual students, draws a cross section/profile of any two points and interpret cross section/profile to determine indivisibility of places on topographical maps |
STEP 4 NOTE TAKING |
The teacher writes a summarized note on the board |
The students copy the note in their books |
NOTE
MAP READING
Calculating gradients and vertical exaggeration
Gradients
Gradients refer to the slope or incline of the terrain. It indicates the rate of change in elevation over a certain distance on a map. Gradients are commonly expressed as a ratio or percentage and help individuals understand the steepness of hills, mountains, or other features on the map.
To calculate gradients, the following specific procedures apply:
Formula for calculating gradient.
Gradient = Difference in height (meters)
Horizontal distance (meters)
Vertical exaggeration
Vertical exaggeration is a factor by which vertical scale is increased or decreased relative to the horizontal scale. It is used to enhance the visibility of elevation differences, making subtle variations more noticeable.
For example, if the vertical exaggeration is set to 2:1, it means that the vertical scale is doubled compared to the horizontal scale. This can be useful in geological cross-sections or topographic profiles to emphasize terrain features like mountains or valleys that might be visually obscured with a realistic scale.
The procedure for calculating vertical exaggeration involves determining the ratio between the vertical and horizontal scales in a graphical representation.
1.Convert the verticalscale into a representative fraction (R.F) or a ratio
2.Write down the horizontal scale of the map also as ratio
3.Divide the horizontal scale by the vertical scale to get the vertical exaggeration.
Formula for calculating exaggeration
Vertical exaggeration = Horizontal Scale
Vertical Scale
Example 1. If the vertical scale of a map is 1cm to 100m (i.e. 1mm to 10m) while the map scale is 1:100,000. Calculate the vertical exaggeration.
Solution
The ratio of vertical scale = 1:10,000
Horizontal scale = 1:1)0,000
Vertical exaggeration = 100,000/10,000 = 10.0
Thus vertical exaggeration = 10.0
Procedures for drawing cross section /profile
Drawing a cross-section or profile involves creating a two-dimensional representation of the Earth's surface along a chosen line. This is particularly useful in geology, geography, and engineering for visualizing the topography and features along a specific transect. The following are the general procedures for drawing a cross-section:
Step1. Take a thin strip of paper and place it along the transect line on the map. Mark A at the start of the transect and B at the end.
Draw a line to connect the two points A and B as seen in the image below.
Step 2: Use a ruler and pencil to draw the horizontal axis of the graph exactly the same length as the transect A-B.
Step 3: Place the strip of paper along the x-axis at the bottom of the graph. Line A and B up with the vertical axes.
Step 4: Plot the heights marked on the piece of paper onto the graph
Step 5: Use a pencil to connect the dots in the graph with a smooth line.
Interpreting cross section/profile to determine indivisibility of places on topographical maps
To determine the indivisibility of places on topographical maps using cross-sections or profiles, analyze the contour lines. If contour lines are closely spaced, indicating steep terrain, the place is likely indivisible.
Conversely, widely spaced contours suggest gentle slopes and divisibility. The vertical exaggeration in profiles helps visualize elevation changes.
EVALUATION: 1. Differentiate between gradients and vertical exaggeration, given formulas.
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively