1. Junior Navigation Chapter 4
Altitude Corrections
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Junior Navigation
Chapter 4

2. Objectives:
■ Understand how the following factors affect altitude observations: dip refraction parallax semidiameter
■ Apply altitude corrections from the Nautical Almanac to observations of the sun.

3. Practical Exercises:
Problems 1. & 2.
Follow the Student Manual for guidance

4. 3. The correction for dip:
a. may be either positive or negative.
b. decreases in magnitude as height of eye increases.
c. is always negative and increases in magnitude as height of eye increases.
d. is always positive and decreases in magnitude as height of eye increases.
Ref: ¶ 5

5. 4. If an observer is taking sights from a pier in an area with a 10-foot tidal range, will his height of eye for computing altitude corrections change over a period of time?
Yes.
What if the observer is on a boat anchored in the same area?
No.
Ref: ¶ 5

6. 5. Which of the following is used as the entering argument to enter altitude correction tables?
a. Sextant altitude (hs).
b. Apparent altitude (ha).
c. Observed altitude (Ho).
Ref: ¶

7. Solution: a. Sun LL, 27 Feb hs 28°15.8'
6. Using the Excerpts from the Almanac, find the observed altitude (Ho) for the following: Date Body hs IC HE Ho
a. 27 February Sun LL 28°15.8' +7.3' ft
b. 17 August Sun UL 21°58.2' +0.7' ft
28°34.9'
21° 32.7'
Solution: a. Sun LL, 27 Feb hs 28°15.8'
IC '
Dip ' ha 28°20.4 '
Main ' Ho 28°34.9'
Solution: b. Sun UL, 17 Aug hs 21°58.2'
IC '
Dip ' ha 21°50.9 '
Main ' Ho 21°32.7'
Ref: ¶

8. 7. Which of the following corrections need to be applied in order to determine apparent altitude?
a. dip and parallax b. refraction and parallax c. index error and semi-diameter
d. dip and index error
Ref: ¶ 20, 26

9. 8. Which of the following corrections are applied to apparent altitude for a sun sight?
a. main correction only
b. main correction plus semi-diameter correction
c main correction plus additional correction
d. main correction, additional correction, and HP
Ref: ¶ 21, 27

10. 9. Two JN students take sights on the sun at approximately the same time from approximately the same location at sea. Mary has a HE of 8 feet and an IC of '. Jane has a HE of 22 feet and an IC of -2.1'. Assuming both are accurate sights, which of the following is true?
a. Jane's sight will have a larger ha than Mary's sight.
b. Mary's sight will have a larger ha than Jane's sight.
c. Jane's sight will have an hs smaller than Mary's sight.
d. The ha for both sights will be about the same.
Ref: ¶ 5,

11. Junior Navigation Chapter 4
Altitude Corrections
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Homework
Q & A
Junior Navigation
Chapter 4