Part One
  Map Reading


  Reading Topographical Maps Introduction 1. HOME

  Topographical Maps - Definition, Purpose and Categories 2. Maps

  Information in the margins of an army map 3. Marginal Information    and Symbols

  Latitude, Longitude and Other Methods to Locate Points on Topographic Maps 4. Grids

  Translating Distance on a Topographic Map to Distance on the Ground 5. Scale and Distance

  Grid North, Azimuth, Declination And Other Concepts Used To Find Direction With Topographic Maps 6. Direction

  Overlays - Used Primarily In Army Map Reading 7. Overlays

  Aerial Photographs - Supplements And Substitutes For Topographic Maps 8. Aerial Photographs

 Part Two
  Land Navigation


  Using Compass, GPS, Sun, Shadows, and Stars in Land Navigation 9. Navigation Equipment    and Methods

  Reading The Shape Of The Land In Topographic Maps 10. Elevation and Relief

  Orienting and Navigating With Topographic Maps 11. Terrain Association

  Mounted Land Navigating With Motorized Vehicles 12. Mounted Land    Navigation

  Land Navigation In Different Types of Terrain 13. Navigation in    Different Types of    Terrain



  Sketching Topographic Maps A. Field Sketching

  Folding Topographic Maps B. Map Folding     Techniques

  Units of Measure and Conversion Factors Used in Reading Topographic Maps C. Units of Measure and      Conversion Factors

  Units of Measure and Conversion Factors Used in Reading Topographic Maps D. Joint Operations      Graphics

  US Army Training Material for Map Reading and Land Navigation E. Exportable Training      Material

  Orienteering F. Orienteering

  US Army M2 Compass G. M2 Compass

  Additional Aids such as Night Vision Goggles and Global Positioning System or GPS H. Additional Aids      (GPS, Night Vision)

  Global Positioning System -  GPS J. Global Positioning      System - GPs

 

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8-2. TYPES OF AERIAL PHOTOGRAPHS

Aerial photography most commonly used by military personnel may be divided into two major types, the vertical and the oblique. Each type depends upon the attitude of the camera with respect to the earth's surface when the photograph is taken.

a.   Vertical. A vertical photograph is taken with the camera pointed as straight down as possible (Figures 8-1 and 8-2). Allowable tolerance is usually + 3° from the perpendicular (plumb) line to the camera axis. The result is coincident with the camera axis. A vertical photograph has the following characteristics:

(1)   The lens axis is perpendicular to the surface of the earth.

(2)   It covers a relatively small area.

(3)   The shape of the ground area covered on a single vertical photo closely approximates a square or rectangle.

(4)   Being a view from above, it gives an unfamiliar view of the ground.

(5)   Distance and directions may approach the accuracy of maps if taken over flat terrain.

(6)   Relief is not readily apparent.

Figure 8-1. Relationship of the vertical aerial photograph with the ground.

Figure 8-1. Relationship of the vertical aerial photograph with the ground.

 

Figure 8-2. Vertical photograph.

Figure 8-2. Vertical photograph.

a.   Low Oblique. This is a photograph taken with the camera inclined about 30° from the vertical (Figure 8-3, and Figure 8-4). It is used to study an area before an attack, to substitute for a reconnaissance, to substitute for a map, or to supplement a map. A low oblique has the following characteristics:

(1)   It covers a relatively small area.

(2)   The ground area covered is a trapezoid, although the photo is square or rectangular.

(3)   The objects have a more familiar view, comparable to viewing from the top of a high hill or tall building.

(4)   No scale is applicable to the entire photograph, and distance cannot be measured. Parallel lines on the ground are not parallel on this photograph; therefore, direction (azimuth) cannot be measured.

(5)   Relief is discernible but distorted.

(6)   It does not show the horizon.

Figure 8-3. Relationship of low oblique photograph to the ground.

Figure 8-3. Relationship of low oblique photograph to the ground.

 

Figure 8-4. Low oblique photograph.

Figure 8-4. Low oblique photograph.

c.   High Oblique. The high oblique is a photograph taken with the camera inclined about 60° from the vertical (Figures 8-5 and 8-6). It has a limited military application; it is used primarily in the making of aeronautical charts. However, it may be the only photography available. A high oblique has the following characteristics:

(1)   It covers a very large area (not all usable).

(2)   The ground area covered is a trapezoid, but the photograph is square or rectangular.

(3)   The view varies from the very familiar to unfamiliar, depending on the height at which the photograph is taken.

(4)   Distances and directions are not measured on this photograph for the same reasons that they are not measured on the low oblique.

(5)   Relief may be quite discernible but distorted as in any oblique view. The relief is not apparent in a high altitude, high oblique.

(6)   The horizon is always visible.

Figure 8-5. Relationship of high oblique photograph to the ground.

Figure 8-5. Relationship of high oblique photograph to the ground.

 

Figure 8-6. High oblique photograph.

Figure 8-6. High oblique photograph.

d.   Trimetrogon. This is an assemblage of three photographs taken at the same time, one vertical and two high obliques, in a direction at right angle to the line of flight. The obliques, taken at an angle of 60° from the vertical, sidelap the vertical photography, producing composites from horizon to horizon (Figure 8-7).

Figure 8-7. Relationship of cameras to ground for trimetrogon photography (three cameras).

Figure 8-7. Relationship of cameras to ground for trimetrogon photography (three cameras).

e.   Multiple Lens Photography. These are composite photographs taken with one camera having two or more lenses, or by two or more cameras. The photographs are combinations of two, four, or eight obliques around a vertical. The obliques are rectified to permit assembly as verticals on a common plane.

f.   Convergent Photography. These are done with a single twin-lens, wide-angle camera, or with two single-lens, wide-angle cameras coupled rigidly in the same mount so that each camera axis converges when intentionally tilted a prescribed amount (usually 15 or 20°) from the vertical. Again, the cameras are exposed at the same time. For precision mapping, the optical axes of the cameras are parallel to the line of flight, and for reconnaissance photography, the camera axes are at high angles to the line of flight.

g.   Panoramic. The development and increasing use of panoramic photography in aerial reconnaissance has resulted from the need to cover in greater detail more and more areas of the world.

(1)   To cover the large areas involved, and to resolve the desired ground detail, present-day reconnaissance systems must operate at extremely high-resolution levels. Unfortunately, high-resolution levels and wide-angular coverage are basically contradicting requirements.

(2)   A panoramic camera is a scanning type of camera that sweeps the terrain of interest from side to side across the direction of flight. This permits the panoramic camera to record a much wider area of ground than either frame or strip cameras. As in the case of the frame cameras, continuous cover is obtained by properly spaced exposures timed to give sufficient overlap between frames. Panoramic cameras are most advantageous for applications requiring the resolution of small ground detail from high altitudes.

8-3. TYPES OF FILM

Types of film generally used in aerial photography include panchromatic, infrared, and color. Camouflage detection film is also available.

a.   Panchromatic. This is the same type of film that is used in the average hand-held small camera. It records the amount of light reflected from objects in tones of gray running from white to black. Most aerial photography is taken with panchromatic film.

b.   Infrared. This is a black-and-white film that is sensitive to infrared waves. It can be used to detect artificial camouflage materials and to take photographs at night if there is a source of infrared radiation.

c.   Color. This film is the same as that used in the average hand-held camera. It is limited in its use because of the time required to process it and its need for clear, sunny weather.

d.   Camouflage Detection. This film is a special type that records natural vegetation in a reddish color. When artificial camouflage materials are photographed, they appear bluish or purplish. The name of this film indicates its primary use.


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Books

Map Reading and Land Navigation Buy the book this website is based on: Map Reading and Land Navigation

This website is based on the US Army Field Manual: "Map Reading and Land Navigation" Buy a copy from Amazon.com to take with you out in the field.

 

Book Review - Be Expert with Map and Compass

One of the best ways to learn and become proficient in any subject is to find a way to make a game or sport of it. That's exactly what orienteering does! Orienteering began to develop almost 100 years ago in the Scandinavian countries as a fun and effective method for military training in land navigation. Bjorn Kjellstrom was closely involved with the early development of orienteering, and he is the person who introduced the sport to North America. He, along with his brother Alvar, and a friend named Gunnar Tillander, invented the modern orienteering compass. They manufactured and marketed it as the Silva Protractor compass. This compass, along with Bjorn's book Be Expert with Map and Compass, made it much easier for anyone to learn how to use a map and compass.

This book has become the most widely read classic on the subject of map reading, compass use, and orienteering. Over 500,000 copies have been sold in the english language editions alone. There have been very successful editions published in French, Italian, and other languages as well. It is a short (just over 200 pages), easy to read, enjoyable book that can help you to have fun while you learn the subject quickly and effectively.

The book is organized into four main parts, plus a short, useful introduction. Part 1 covers having fun with maps alone. Then, Part 2 covers having fun with a compass alone. Part 3 puts it together and shows you how to have fun with a map and compass together. This section also introduces the game or sport of orienteering. Part 4 covers competitive orienteering for those who would like to compete with others in the sport.

A reproduction of a segment of an actual topographic map is included as a fold-out in the back of the book. It is used together with the "how-to" instructions the book provides. For example, one of the exercises in Part 3 is an imaginary orienteering "hike" that uses the sample map.

If you would like to have one of the best books available on map reading and using a compass, Be Expert with Map and Compass is hard to beat. You can buy a copy from Amazon.com today.

Read a book review of Agincourt

Boat Navigation For The Rest of Us
  Boat Navigation For The Rest of Us

Basic Coastal Navigation
  Basic Coastal Navigation