Transcript
Page 1: Navigate Using a Map and Compass

Navigate Using a Map and CompassNavigate Using a Map and Compass

COURSE: BMQ (P Res)COURSE: BMQ (P Res)EO: 012-01 dEO: 012-01 d Rank/Name:Rank/Name:

Time: toTime: to Reference:

B-GL-382-005/PT-002 Chapter 3, Section 1, paras 1–8; Section 2, paras 9–14

1.1. Measuring Distance on a MapMeasuring Distance on a Map

a) Definition of Map Scaleb) Measuring Straight-line

Distancesc) Measuring Road Distances or

Distances Not in a Straight Line

Page 2: Navigate Using a Map and Compass

Navigate Using a Map and CompassNavigate Using a Map and Compass

1.1. Measuring Distance on a MapMeasuring Distance on a Map

a) Definition of Map Scaleb) Measuring Straight-line Distances c) Measuring Road Distances or

Distances Not in a Straight LineTPTP

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1) Definition of scale

a. The scale of a map is the relationship between the horizontal distance between two points measured on the ground and the same two points measured on the map. This relationship is constant no matter which direction the distances are measured.

a)Definition of Map ScaleNavigate Using a Map and CompassNavigate Using a Map and Compass

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2)2) Methods of expressing scaleMethods of expressing scale

a.a. There are two methods used for There are two methods used for expressing the scale of a map:expressing the scale of a map:1)1) by the representative fraction: by the representative fraction:

for example, 1:50 000; orfor example, 1:50 000; or2)2) in words: for example, one in words: for example, one

inch to four miles.inch to four miles.

Navigate Using a Map and CompassNavigate Using a Map and Compassa)Definition of Map Scale

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3)3) Representative fractions (RF)Representative fractions (RF)a.a. The RF is the standard method of expressing a The RF is the standard method of expressing a

scale on all Canadian Maps and must be scale on all Canadian Maps and must be understood by all map users. The RF is 1:X, one understood by all map users. The RF is 1:X, one unit of distance on the map will represent X unit of distance on the map will represent X units of distance on the ground.units of distance on the ground.

b.b. For example, a scale of 1:50 000 means that For example, a scale of 1:50 000 means that one in./cm/m on the map represents 50 000 one in./cm/m on the map represents 50 000 in./cm/m on the ground. The essential in./cm/m on the ground. The essential connection is that the same unit of connection is that the same unit of measurement applies both to the map and to measurement applies both to the map and to the ground measurement. For example a the ground measurement. For example a distance of 3 centimetres on a 1:50 000 scale distance of 3 centimetres on a 1:50 000 scale map represents 3 times 50 000 centimetres on map represents 3 times 50 000 centimetres on the round, that is 150 000 centimetres or 1 500 the round, that is 150 000 centimetres or 1 500 metres.metres.

Navigate Using a Map and CompassNavigate Using a Map and Compassa)Definition of Map Scale

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4)4) Scales expressed in wordsScales expressed in wordsa.a. The use of scales expressed in words is The use of scales expressed in words is

obsolescent but is still in use and must also be obsolescent but is still in use and must also be understood. The most common example is the understood. The most common example is the one inch to one mile map. In this case, one inch one inch to one mile map. In this case, one inch on the map represents one mile on the ground. on the map represents one mile on the ground. If a direct comparison is required in metres, it If a direct comparison is required in metres, it is necessary to turn the scale into its is necessary to turn the scale into its representative fraction 1:63 360, i.e., one inch representative fraction 1:63 360, i.e., one inch equals 63 360 inches or one mile; therefore: 1 equals 63 360 inches or one mile; therefore: 1 centimetre = 63 360 centimetres = 633.6 centimetre = 63 360 centimetres = 633.6 metresmetres

b.b. For smaller-scale maps such as the “quarter-For smaller-scale maps such as the “quarter-inch,” the scale can be expressed as either ¼ inch,” the scale can be expressed as either ¼ inch to one mile, or four miles to one inch. The inch to one mile, or four miles to one inch. The smaller the scale, however, the more likely one smaller the scale, however, the more likely one is to use the form “miles to the inch.”is to use the form “miles to the inch.”

Navigate Using a Map and CompassNavigate Using a Map and Compassa)Definition of Map Scale

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5) Comparison of map scalesa. Typically maps with scales of

1:50 000 and less are considered “large scale,” and maps with scales of 1:100 000 and greater are considered “small scale.”

Navigate Using a Map and CompassNavigate Using a Map and Compassa)Definition of Map Scale

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6) Effects on a map of a change in scalea. It is important to realize, when map

reading, the effects of a change of scale from a map with a scale of say 1:50 000 to one of 1:250 000. It is obvious that the distance between two identical points on the maps will be reduced to one-fifth when changing from the larger to the smaller scale. It is not so obvious that this reduction of the distances takes place in all directions equally, and that consequently both sides of a rectangle will also be reduced to one-fifth and the resultant area will be 1/25 of the area on the larger scale map. Similarly, the space between items of detail will be proportionately reduced, and detail will appear more congested.

Navigate Using a Map and CompassNavigate Using a Map and Compassa)Definition of Map Scale

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Do you have any

questions?

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Q1: What is the difference between a 1:50 000 scale map and a 1:25 000 scale map?

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A1: The details on the 1:25 000 scale map will be easier to describe and more visible.

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Navigate Using a Map and CompassNavigate Using a Map and Compass

1.1. Measuring Distance on a MapMeasuring Distance on a Map

a) Definition of Map Scaleb) Measuring Straight-line Distancesc) Measuring Road Distances or

Distances Not in a Straight LineTPTP

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1) Scales on mapsa. All maps carry graphic linear scales

(usually in the middle of the lower margin) from which any horizontal distance may be measured on the map in statute miles, kilometres, metres, yards and nautical miles. These may appear in various combinations and various sizes depending on the type and scale of the map sheet.

Navigate Using a Map and CompassNavigate Using a Map and Compassb)Measuring Straight-line Distances

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2) Measuring a straight-line distancea. To measure a straight-line distance between

two points, place a straight edge of a piece of paper against the two points and at each point mark the paper. Then, place the paper along the scale line on the map with the right hand mark against one of the major divisions so that the left hand mark lies against the sub-divisions to the left of the zero on the scale. The total distance is then the number of major divisions plus the distance measured to the left of the zero.

Navigate Using a Map and CompassNavigate Using a Map and Compassb)Measuring Straight-line Distances

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3) Use of separate scalesa. Separate scales such as those on the C2

protractor (see Figure 6-4) may be used for measuring short distances on maps. It must be remembered when measuring long distances, that the paper of a map may stretch or shrink quite appreciably, while a metal, plastic or wooden scale does not. The scale drawn on the map stretches or shrinks with the map, and therefore always provides a scale in conformity with the map detail.

Navigate Using a Map and CompassNavigate Using a Map and Compassb)Measuring a Straight-line Distance

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Navigate Using a Map and CompassNavigate Using a Map and Compass

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4) Use of grid linesa. Most military maps carry grid lines.

The grid lines are a fixed distance apart and may be used to make quick estimations of distances between two points. Separate scales may be checked against the grid lines before use to make sure that the map and the scale agree.

Navigate Using a Map and CompassNavigate Using a Map and Compassb)Measuring Straight-line Distances

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Do you have any

questions?

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Q1: What is the distance between Grid Ref A __________ and Grid Ref B________?

Q2: What is the distance between Grid Ref A __________ and Grid Ref C________?

Q3: What is the distance between Grid Ref E __________ and Grid Ref B________?

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A1:

A2:

A3:

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Navigate Using a Map and CompassNavigate Using a Map and Compass

1.1. Measuring Distance on a MapMeasuring Distance on a Map

a) Definition of Map Scaleb) Measuring Straight-line Distances c) Measuring Road Distances or

Distances Not in a Straight LineTPTP

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1) Measuring a road distancea. To measure a distance that is not

straight (for example along a road), consider the road as a number of straight or nearly straight sections and proceed as follows:1. Lay a piece of paper along the first section;2. Mark it with a tick at the starting point and

another at the end of the first section;

Navigate Using a Map and CompassNavigate Using a Map and Compassc) Measuring Road Distances or

Distances Not in a Straight Line

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3. Then pivot the paper about the second tick until it lies along the second section;

4. Mark the end of the second section with another tick, and repeat the process until the last point is marked; and

5. Read off the paper against the scale

Navigate Using a Map and CompassNavigate Using a Map and Compassc) Measuring Road Distances or

Distances Not in a Straight Line

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Do you have any

questions?

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Q1: What is the distance between …?

Q2: What is the distance between …?

Q3: What is the distance between …?

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A1:

A2:

A3:

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Navigate Using a Map and CompassNavigate Using a Map and Compass

COURSE: BMQ (P Res)COURSE: BMQ (P Res)EO: 012-01 dEO: 012-01 d Rank/Name:Rank/Name:

Time: toTime: to Reference:

B-GL-382-005/PT-002 Chapter 3, Section 1, paras 1–8; Section 2, paras 9–14

1.1. Measuring Distance on a MapMeasuring Distance on a Map

a) Definition of Map Scaleb) Measuring Straight-line

Distances c) Measuring Road Distances or

Distances Not in a Straight Line


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