Topographic Map Notes

FIELD- Area where a value is measured.

ISOLINES- a line connecting points of equal value.

Examples of isolines:

Isotherms: points of equal temperature

Isobar: points of equal barometric (air) pressure

Contour Lines: points of equal elevation

Isohyet: Points of equal rainfall

Anything else you can get a value for.

(The weather channel loves isolines!)

Rules for Drawing Isolines:

1. All points on the line MUST have the same value

15

5 5

1510

1010

10

2. Isolines are gentle, curving lines- no sharp corners.

15

5 5

1510

1010

10

3. Isolines are always closed curves even though the map might only show part of it.

4. Isolines NEVER cross- this would mean that one point has two different values.

20°

30 °

40 ° 50 ° 60 °

X

YZ

5. Isolines usually have a parallel trend

6. The interval between 2 isolines must stay constant

40

50

60

30

25

6. We can infer any value that exists between 2 lines

20

30

*X*Y

*Z

8. Index Contour Lines

Every 4th or 5th contour line is thicker and bolder and the elevation is shown on the line

9. Depression contour lines show areas

where land sinks down-

represented by…

What are the rules concerning hachured

lines?

10. Rivers / StreamsWhen a contour line crosses a river or stream they bend upstream Towards where the water comes from!!

11. Gradient shows how quickly the value changes from one point to another.

How STEEP the hill or mountain is

A steep (high) gradient- lines are close together.A gentle (low) gradient - lines are far apart.

Steep areaGentle area

Gradient can be calculated using the formula

The elevation of Albany is 282 feet. The elevation at Binghamton is 1634 feet. Calculate the gradient to the nearest tenth

of a ft/mi. Show all work.

gradient = change in elevation distance

= 1634-282 115 miles

= 1352 ft 115 miles

= 11.8 ft/mile

The elevation of Watertown is 99m. The elevation at Oswego is 144m.

Calculate the gradient to the nearest tenthof a m/km. Show all work.

gradient = change in elevation distance

= 144 - 99 75 km

= 45 m 75 km

= 0.6 m/km

If the distance between the two

circled cities is 425 km, calculate the temperature

gradient to the nearesthundredth?

Show all work.

gradient = change in temperature distance

= 82-48 425

= 34 425

= 0.08 °F/km

Practice drawing isolines

Highlight all the data points with the same value.

Fill in gaps in data.

Connect the dots.

Go on to the next value.

Now try Practice 2!!!!!

Topographic Profiles

Profiles show the side view of the land

Please match the contour map on the left with the profile on the right.

What are the steps to draw a

topographic profileplace a piece of SCRAP paper between the 2

points

MARK where every contour line

touches the edge of the paperdetermine the elevation of each

markplace the paper on the graph and PLOT

the elevation of each contour line