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
