Originally published in 1952, this book is intended as an introductory guide to aerial mapping and photogrammetry. The main emphasis is on making maps during wartime, when accuracy is paramount and information may be minimal; Trorey had experience of this while serving with the Canadian Military Survey in WWII. This book will be of value to anyone with an interest in mapmaking.

List of tables xiv

Bibliography xv

Notation xvi

1.Perspective principles

Photogrammetry,1. Anharmonic Ratios,4. The Scheimpflug Condition,6.

2.Measurement of angles from obliques

Classification of Air-Survey Photographs, 7. Dip of the Horizon,8. Azimuth and Depression Angles from Obliques, Graphical Method, 10. Analytical Method of Obtaining Azimuth and Depression,16. Oblique Plotting Instruments: the Burns Plotter, 17. Azimuth Grid, 19. Coné"ruction of Rectangular Azimuth Grid, 19. Ground-Survey Photographs, 22.

3.Perspective grid and four-point methods

Perspective Grids, 23. Proof of hy and hD For mulae, 25. Standard Grids, 26. Plotting of Forward Oblique Strips (Perspective Grid), 27. Projection of Perspective Grid on Plane containing Three Control Points, 29. Control, 30. Four-point Method, Drill, 31. The Use of the Four-point Method for Minor Control, 32. Shore-line Mapping, 34.

4.Measurement of height from a single oblique

Height-Displacement Formulae, 37. Drill for Semi-graphic Height Determination,37. Heighting Grids,40. Determination of Height of Aircraft, and Measurement of Sloping Objects, by means of the Canadian Oblique Analyser, Mk. III,49. Summary of the Uses of Obliques, 54.

5.Verticals: fundamental considerations of cover, parallax and stereoscopy

Verticals,56. Parallax,58. Binocular Vision and the Stereoscope,62. The Use of the Parallax Bar to determine Parallax Differences,67.

6.Parallax and elevation calculations

Determination of Elevation Differences,Simple Case,71. Standard Heighting Drill, Right Angles to Base-line,72. Contouring,74. Correction by Observation of K,75. Parallax Scale,81. Observational and other Errors and their Magnitude,85. Survey Analogy to Heighting Problem,8s. Focal Length and Parallax,Model Effects, 87. Limitations of Photogrammetric Methods,9o.

7.Radial-line triangulations, graphical and mechanical

The Radial-line Plot, Base-lining and Point Transference,93. Drawing the Radialline Plot,94. Error and its Adjustment,98. The Slotted Templet,101. Calculation of Slotted Templet Accuracy, 105.

8.Rectification means

Rectification,t09. Rectification by Virtual Image, 110. Other Uses of Rectified Photographs,I14.

9.Subdivisions of an air survey mapping operation

Maps and Surveys, 115. Interpretation for Mapping, 117. Interpretation for Special Purposes,118. Subdivisions of an Air Survey Mapping Operation,119. A Specific Mapping Procedure, 120.

10.Principles of stereoscopic plotting instruments

Height Displacement,122. Principles of Automatic Plotting Machines, 123. Orientation,127.

11.The multiplex projector

The Instrument and its Ancillary Equipment,131. Adjustment of Closure in Bridging, 134. Comparative Precision of Various Instruments, 140. Air-Survey Costs, 142. The Mapping Role of the Multiplex, 143.

Appendix 1. Standard mapping procedure Royal Canadian Engineers

INTRODUCTION, I48.

PROCEDURE IN DETAIL, 148.

      1. Control,148.

      1.10. Master Grid. 1.20. Minor Control Plot. 1.30. Ground Control.

      2. Interpretation, 149.

      2.0. Introduction. 2.1. Colour Code. 2.2. Interpretation Drill. 2.4. Remaining Interpretation. 2.5. Checks by Interpreter Himself. 2.6. Responsibility.

      3. Compilation Drill, 152.

      3.1.Transference of Control. 3.2.Setting up in Rectifier,and transferring detail. 3.3. Joining Strip Blocks,Checking. 3.4. Checking of Compilation. 3.5. Churches. 3.6. Preparation of Pencil Compilation for Camera.

      4. Topography,155.

      4.2. Stereo-comparagraphs. 4-3.Topographic Compilation.

      5. Camera and Helio,Preparation of Blues,16o.

      5.1.Fair-drawing Medium and Scale. 5.2.Ferro-prussiates.

      6.Fair-Drawing,161.

      7. Final Photography and First Proof,164.

      7.1.Camera work. 7.2.Proof. 7.3.Proof-reading and Photo-writing

      PROOF-READINC FORMS,166.

      Form 1,Surround Check to Fair-Drawing. Form 2,Edge Check. Form 3, Surround. Form 4, Detail. Form 5, Contours. Form 6, Water.

Appendix 2. Multiplex and stereoplainigraph: considerations governing minimum contour interval 172

Appendix 3. The Kelsh plotter 175

Index 177

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