SAR Fundamentals/Navigation instruments theory
From PCSAR
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SAR workers use navigation instruments to make measurements in the field. | SAR workers use navigation instruments to make measurements in the field. | ||
Revision as of 00:45, 30 December 2012
Contents |
Subject
What is this lesson plan about?
This lesson gives the students a theoretical (class room) understanding of the instruments that they may be using in the field to aid navigation.
The instruments covered are:
- compass
- GPS
- altimeter
- stride tally counter
For each instrument, the theory of how it operates is discussed along with how to select an instrument for purchase.
Only basic use of a GPS is shown. Advanced features such as waypoints, tracks and maps are left to another lesson beyond the SAR Fundamentals course.
Authors
List who wrote this lesson plan.
- Brett Wuth
Scope
What is included in this lesson, what's not and why.
- SAR Fundamentals Ch.13 "Navigation"
- Basic SAR Skills Manual: Ch.7 "Navigation"
- stride count
Prerequisites
What should students already know/have accomplished before the lesson is presented.
Prior to this lesson, students should have already been introduced to the following concepts:
- direction measured in degrees
- directions measured from True North (this lesson will introduce declination and magnetic north)
Parts of a compass which can be used on a map
- straight edge
- ruler
- rotatable bezel and interior north-south lines
- roamer
- magnifying lens
Specifying a location in UTM
- the three components of a UTM: Zone, Easting, Northing
- map datums: NAD27 vs WGS84
- the 6 digit short form of UTM
elevation
- contour lines
Objectives
At the conclusion of this lesson the participants:
- will be able to ...
Time Plan
Total Time: 90 minutes
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00:00 3 min |
Introduce topic title Introduce Instructor Present Objectives |
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00:03
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InstrumentsSAR workers use navigation instruments to make measurements in the field. The measurements are used to calculate your location or that of other things. The four instruments we will discuss:
No one instrument is perfect. Each is better in some circumstances. Each instrument has a different way of failing.
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Compass So far having been using the compass on the map. Can also be used in the field. Because of magnetic needle.
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Magnetic North, Declination The needle of the compass points in the direction of Magnetic North. This is not the same as True North. The difference between True North and Magnetic North is called Declination. It's expressed in degrees and fractions of degrees (minutes). If Magnetic North is to the west of True North, the declination is degrees WEST. Opposite is degrees EAST.
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What direction is Magnetic North? Magnetic North points in the direct of Earth's North Magnetic Pole. It's also somewhat altered by regional geomagnetic features. The North Magnetic Pole isn't the same location as the north pole. North Magnetic Pole is currently (2012) 85.9 deg N 147.0 deg W northwest of of the tip of Ellsmere Island. It moves. About 55 km closer to Russia each year.
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Finding declination Declination changes from year to year. It also changes from area to area. Because North Pole and the North Magnetic Pole appear further apart or closer together depending on where you are located. In our area, declination increases:
Calculation on topo maps is old, not accurate. Ask the person briefing you.
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Compass failures Compasses don't work: when there's magnetic distrubances
attracted to certain metals (iron, nickel, cobalt, alloys like steel)
when the needle doesn't settle
when the needle scrapes the housing
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Choosing a compass Features to look for in compass:
Good compasses:
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GPS
Image:GPS-lesson-plan.odt (pdf)
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WAAS
Altitude/Azimuth calculator for WAAS geosynchronous satellites
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Aids
What materials are needed or useful in presenting this lesson.
- compasses for students
- 5 Pincher SAR Garmin eTrex GPS's
- 1 Brett Wuth's Garmin eTrex GPS
- 5 copies topo map of locale (82 H/5)
- copy for each student of local street map
- copy for each student of PCSAR Doc-69 GPS - Set-Up and Maintenance
- copy for each student of outside exercise sheet, adapted to locale
- Radios
Question bank
List of questions suitable for an review/exam of this section.
Frequently Asked Questions
What are some of the questions that students typically ask. Include the answers.
- How does global compass work at any latitude?
From http://www.mapworld.co.nz/global.html
In the global compass, this problem has been solved with a structural innovation. The needle and magnet are built as separate units functioning independently from each other, so that the inclination of the magnetic field cannot tilt the needle. The needle can no longer move vertically. It is the compass magnet, separated from the needle, which absorbs the vertical force of the magnetic field. The needle itself is fixed at the lid by means of a double jeweled bearing. The magnet rotates with its jewel bearing on a pin. Such a compass works reliably in all zones of the world. Due to the strong magnet, the needle settles very quickly and stops immediately at the right position, allowing for an extremely accurate reading.
Feedback
When has this lesson been presented. What was the feedback.
License
What can others do with this lesson?
Recommended license below. Fill in the year and the author's name(s):
Copyright © YEAR, Author. This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 Canada License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/2.5/ca/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
Reference Material
If you need to cite sources, do so here.
[1]
Notes
Any additional notes, etc.
