Photographic surveying : including the elements of descriptive geometry and perspective

Preface

The first edition of this book was issued in 1889. It was prepared solely for the use of the surveyors employed by the Department of the Interior on photographic surveys ; the edition of fifty copies was lithographed in the surveys office. Some copies found their way outside, and, owing to the favourable comments which they received, the whole edition was exhausted in less than a year. Photographic surveys have since been undertaken for many purposes which were not contemplated at their inception, and a new edition of the book has become necessary for the guidance of the surveyors engaged in the work.

The photographic method is known by many names : photogrammetry, metrophotography, topophotography, iconometry, etc.

It seems that iconometry is the most appropriate name, because it expresses the principle of the method, which is to measure by means of perspectives. Whether the perspectives are photographs, or whether they are produced otherwise, is immaterial so far as the method is concerned. Neither this term nor any other has yet been generally adopted.

The conception of this method is due to Laussedat : his first experiments were made in 1849, the perspectives being drawn with a camera lucida. His paper on the subject, written in 1850, was published in 1854. Shortly after, he substituted photography fbr the camera lucida. He gave a full exposition of the method in various papers, and his work was so complete that little has been added to it since. Wherever photographic surveys are now made, they are executed by the application of the principles laid down by Laussedat.

In Germany, Meydenbauer was the first to give his attention to the new method. His investigations, commenced in 1865 or thereabouts, were continued by Jordan, Hauck, Koppe and many others.

In Italy, the celebrated engineer Porro, who was acquainted with Laussedat and knew his work, proposed for surveying purposes, a

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PHOTOGRAPHIC SURVEYING.

camera built to receive spherical plates. The idea was not practical and was never carried out. In 1875 and 187 6, some experiments were made by Lieutenant Manzi Michele, but they were not favourably received. To Major General Annibale Ferrero, Director of the Geographical Military Institute, is due the credit of initiating the ordnance photographic surveys of the present day. Their execution was entrusted to engineer L. Pio Paganini with a staff of able assistants. The work of the institute is very remarkable and deserves careful study.

In Austria, the first important surveys were made by Mr. Yincenz Pollack, chief engineer of the state railways. Some beautiful mountain maps have lately been printed by Giesecke and Devrient, of Leipzig, for the German and Austrian Alpine club. They are the work of S. Simon. He made use of the original ordnance survey, filling in the topographical details from photographs. These maps represent one of the most successful applications of photographic surveying. Schiffner’s and Steiner’s writings on the subject are among the best, and the Austrian instrument makers, such as It. Lechner or Starke and Kammerer, have surveying cameras of many patterns to select from.

It is in Canada that the method has received its most extensive application; it was first employed when the surveys of Dominion lands were extended to the Pocky Mountains. In the prairies, our operations are limited to defining the boundaries of townships and sections ; these lines form a network over the land by means of which the topographical features, always scarce in the prairies, are sufficiently well located for general purposes.

In passing to the mountains, the conditions are entirely different. The topographical features are well marked and numerous ; the survey of the section lines is always difficult, often impossible, and in most cases useless. The proper administration of the country required a tolerably accurate map, and means had to be found to execute it rapidly and at a moderate cost. The ordinary methods of topographical surveying were too slow and expensive for the purpose ; rapid surveys, based on triangulations and sketches, were tried and proved ineffectual ; then photography was resorted to.

Up to 1892, the photographic surveys were confined to the Rocky Mountains, in the vicinity of the Canadian Pacific Railway ; at the

PREFACE .

v end of that year, they covered about 2,000 square miles. In the same year, an International Boundary Commission was appointed to examine the country along the boundary between Canada and the United States Territory of Alaska. The Canadian Commissioner, Mr. W. F. King, decided to carry out his share of the work by photography. In 1893 and 1894, his parties surveyed about 14,000 square miles.

Irrigation surveys were commenced last year in the south-westerly part of the North- west Territories, where the rainfall is not quite sufficient for agricultural purposes. In addition to the gauging of streams, the establishment of bench marks, etc., it is necessary to ascertain the catchment areas and to define the sites best adapted for reservoirs. For this purpose photography has again been resorted to in the foot hills and on the eastern slope of the mountains. It has, in this case, a peculiar advantage. Whether or not a site is a favourable one for a reservoir cannot be known until the plan has been partly plotted. It must be possible to bring water to the proposed place and to run it off; the capacity must also be adequate. If favourable, a detailed survey of the site is required. With the ordinary surveying instruments, a preliminary survey has to be made ; if, after plotting it, the site is found favourable, the topographer has to go over the ground a second time to make a detailed survey. Or, the whole *bf the work may be executed at once, with the contingency that the detailed survey may turn out useless. With the camera, the plan may be plotted so far, and so far only, as required ; the photographs which furnish a general plan, can be made to give all the detail wanted without going again into the field. Whether the site is a good one or not, there is no labour wasted.

Notwithstanding the many publications on photographic surveying, the great advantages assigned to it and the numerous experimental surveys executed, it has not yet come into general use ; in many quarters there is still an adverse feeling against it. There is such a fascinating simplicity about the method that it is at first difficult to understand the reasons which prevent its adoption. Can anything more convenient be conceived than a method which enables a topographer to gather rapidly on the ground the material for his maps and to construct them afterwards at leisure in his office ? In the first edition of this book, I endeavoured to explain this anomaly. The large scales of viii

PHOTOGRAPHIC SURVEYING.

In the climate of the Rocky Mountains, where the work under my direction has been executed, one half of the number of days during a season is lost through smoke, fog, rain and snow storms, and our experience is that it takes three days in the office to plot the work of one day in the field. Thus for every day’s work in the field, there is another day lost, on account of the weather and three days spent in the office, or five days altogether.

Assuming that the plane table can be used in the field whenever the weather is fair enough for the camera, which is not the case, also that the topographer can plot and draw in the field as quickly as in the office, where he has every convenience at hand, the same survey by the plane table would require the same length of time at actual work or four days. To this we must add four days lost on account of the weather, or eight days altogether.

The cost of our parties in the field is $20.50 per diem : at office work the only expense is the salary of the topographer, $5.00 per diem. Summing up we find the comparative cost as follows :

PLANE TABLE.

8 days in the field, at $20.50 per diem $164

CAMERA.

2 days in the field, at $20.50 per diem $41

$56

This shows that the plane table survey would cost at least three times as much as the camera survey. In reality the difference is greater, because part of the work, as well on the ground as in the office, is executed by the assistant, an arrangement which cannot very well be made with the plane table. The figures above are derived from our practice ; with more views or more detailed plotting, the difference in cost would be still more in favour of the camera.

If we analyse the causes of the superiority of the camera, we find that a very small portion of the topographer’s time is spent in surveying operations. Nearly the whole of it is devoted to travelling for

PREFACE.

IX the purpose of seeing the country and he can map all that he, or rather his camera, can see. His work consists of two distinct parts ; on the ground, he simply collects data, and, with the exception of a few angles, does not waste any of his time in plotting or making measurements. This is left for the office, where the only expenses are the salaries of the surveyor and assistant. In the next place, the party consisting of an assistant and two men is, if not smaller, at least as small and inexpensive as for any other kind of survey. One man is sufficient to carry our camera and tripod almost anywhere, while an ordinary plane table, if it could be taken where our camera has been, could not be carried there by any single man.

It is objected that plotting from photographs is more laborious than plotting on the plane table. There is indeed a slight additional labour ; against this may be set off the fact that no useless line is ever drawn, as when, on the plane table, a point is sighted upon which cannot be recognized from the next station. The greater convenience of working in an office, instead of in the open air, turns the scale in favour of the camera. But photography has an overwhelming advantage in the numerous processes which the laws of perspective place at the disposal of the topographer. The plane table cannot compete with the perspectometer or the perspectograph.

Another objection is, that points cannot be so easily identified on photographs, nor the forms of the surface so truly represented, as when the topographer has the ground under his eyes. This is a mistaken idea ; there is no difficulty whatever in identifying any number of points on moderately good photographs, and, moreover, the topographer does not need, as with the plane table, to trust to his memory in order to recognize them. The undulations of the ground are, it is true, less distinct on the photographs, but this is more than compensated by the advantage of having, side by side, views of the same place from several stations.

The practice of photographic surveying requires a thorough knowledge of descriptive geometry and perspective. These sciences are not included in the programme of examination of Dominion Land Surveyors, and, as it is for them that this book is prepared, I deem it proper to explain the principles of both in a concise form, keeping in view the special purpose of their application to Perspective Surveying.

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PHOTOGRAPHIC SURVEYING.

I have reproduced, as nearly in their own words as possible, the remarkable investigations of Messrs. Hurter and Driffield ; they represent the most important advance in photography during recent years, and may be given as a model of accurate scientific research. An intimate understanding of their work is indispensable to the photographic surveyor.

A few explanations are given on the principles and mode of action of photographic lenses ; the description of anastigmats and of their peculiarities is from a lecture by their inventor, Dr. Paul Rudolf.

Considerable space is devoted to perspective instruments ; as now constructed, they are almost useless for purposes of topographical surveying, but, there is no reason why they should not be made sufficiently precise, all that is required being more perfect workmanship. For architectural surveys, they may prove most useful.

A short reference is made to secret and balloon surveying. Of course the subject is of no practical interest to Canadian surveyors, but it is well that those engaged on photographic surveys should have some knowledge of everything pertaining to photographic surveying.

The Canadian Surveys are by far the most extensive that have ever been attempted. For this reason, if for no other, it is hoped this account of their mode of execution will prove acceptable to those interested in the development of the science of Surveying.

E. DEYILLE.

LIST OF THE MOST IMPORTANT PUBLICATIONS ON PHOTOGRAPHIC SURVEYING.

1854. Laussedat. — Memoire sur l’emploi de la chambre claire dans les reconnais sances topographiques. Memorial de l’officier du genie, NQ 16, 1854.

1859. Laussedat. — Analyse d’un memoire sur l’emploi de la photographie dans le leve des plans. Comptes rendus de l’Academie des Sciences, 1859.

1860. Laugier et Daussy. — Rapport sur le memoire de M. Laussedat. Comptes rendus de l’Academie des Sciences, 1860.

1862. PaU. — Application de la photographie a la topographie militaire.

1864. Laussedat. — Memoire sur l’emploi de la photographie dans le leve des plans. Memorial de I’officier du genie. No. 17, 1864.

1866. Jouart. — Application de la photographie aux leves militaires.

1867. Meydenbauer. — Uber die Anwendung der Photographie zu Architektur und Terrain aufnahmen. Zeitschrift fur Bauwesen.

1874. Javary. — Memoire sur l’application de la photographie aux arts militaires. Memorial de l’officier du genie. No. 22, 1874.

1876. Jordan. — Verwerthung der Photographie zu geometrischen Aufnahmen. Zeitschrift fur Vermessungskunde.

1886. Bornecque. — La photographie appliquee au lever des plans.

1888. Reed. — Photography applied to surveying.

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1889. Le Bon. — Les levers photographiques et la photographie en voyage.

1891-93. Steiner. — Die Photographie im Dienste des Ingenieurs.

1892. Legros. — Elements de photogrammetrie.

1893. Pollack. — Die Beziehungen der Photogrammetrie zu den topographischen

1893-94. Laussedat. — Les applications de la perspective au lever des plans — Annales du Conservatoire des Art et Metiers.

Contents

PAGE

Preface iii

List of the most important publications on photographic surveying xi

Chapter I. Descriptive Geometry

1. Definition, planes of projection 1

2. Ground line i

3. Representation of a point 1

4. Representation of a straight line ' 3

5. Through a given point, to draw a parallel to a given line 6

G. Representation of a plane 7

7. Line contained in a plane 8

8. Point in a plane 9

9. Through a point, to draw a plane parallel to another plane 9

10. Line perpendicular to a plane 10

11. Revolving a plane upon one of the planes of projection 10

12. Intersection of two planes 14

13. The intersecting planes are both parallel to the ground line 15

14. The intersecting planes cut the ground line at the same point 15

15. Intersection of two planes, one of which is horizontal or parallel to the ver-

tical plane 16

16. Planes perpendicular to one of the planes of projection 16

17. Intersection of a line and a plane 16

18. Intersection of three planes 17

19. Through a point, to draw a straight line which will meet two given lines. ... 17

20. Distance of two points 17

21. To lay off a given length on a line 17

22. Distance from a point to a line 18

23. Distance from a point to a plane 18

24. Distance of two parallel planes 19

25. Distance of two straight lines 19

26. Angles of a line with the planes of projection 19

27. Angle of two lines 20

28. Angles of a plane with the planes of projection. 20

29. Angle of two planes 21

30. Through a given line in a plane to draw another plane making a certain

angle with the given plane . . . , . .. 22

31. Angle of a line with a plane 22

32. Method of rotations 22

33. Rotation of a point 23

34. Rotation of a line 23

35. Rotation of a plane 23

36. Distance of two points 24

37. Solution of spherical triangles 25

38. Given three sides, to find the angles * 25

39. Given two sides and the included angle, to find the remaining side and angles. 26 dv PHOTOGRAPHIC SURVEYING.

PAGE

40. Given two angles and the side opposite one of them, to find the remaining

sides and angle . . . . . . 26

41. Given two sides and the angle opposite one of them, to find the remaining

side and angles 27

42. Other cases. — Supplementary triangles 27

43. Reduction of an angle to the horizon 28

Chapter II. Perspective

44. General remarks 29

45. Definitions 29

46. Perspective of a point in the ground plane 31

47. Perspective of a line in the ground plane 32

48. Perspective of a point not in the ground plane 32

49. Perspective of a line not in the ground plane .......... .. ........... 33

50. Positions of the vanishing point 34

51. Vanishing line. . -.... 34

52. Lines or figures in front planes. — 35

53. Measuring lines and measuring points ..... ........... 36

54. Reduction of a perspective to scale — 37

55. To place in perspective a point of the ground plane 39

56. To place in perspective a line or figure of the ground plane 40

57. To place in perspective a point outside of the ground plane. ........ ...... 41

58. To place in perspective a line outside of the ground plane 41

59. The distance line is an axis of symmetry of the perspective 41

60. Given the heights of two points and their perspectives, to find the vanishing

point and trace on picture plane of the line joining the given points 42

61. To find the intersections of a vertical line by a series of horizontal planes . . 42

62. To mark on the perspective of any line or curve contained in a vertical plane,

the intersections by a series of horizontal planes 44

63. To mark on the perspective the intersections of a plane, line, or curve, by a

series of horizontal planes ... 45

64. Intersections of a prism, pyramid, or conic surface, by a series of horizontal

planes. — 45

65. To place a point of the ground plane by means of its perspective. 46

66. To place a line on the ground plane by means of its perspective. ....... 46

67. To draw a figure on the ground plane by means of its perspective 47

70. Precision of the method ........... .. 49

71. To determine from the perspective, the projections of a point not in the

ground plane, but of which the height is known 50

72. To construct from its perspective a figure in any horizontal plane. 50

73. To find the traces and vanishing point of a line given by its horizontal pro-

jection and perspective ...... 81

74. Given the slope of a line and the horizontal projection of one of its points, to

find the horizontal projection and traces of the line 52

75. To find the traces of the plane containing three given points or two given

lines 53

76. Given the line of greatest slope, to find the traces of the plane 54

77. Change of ground plane . 54

78. To find the horizontal projection of a figure from its perspective when the

figure is contained in a plane perpendicular to the principal plane 55

79. To find from its perspective the horizontal projection of a figure in. a plane

perpendicular to the picture plane .... ....... 57

80. Change of ground plane and distance line 59

CONTENTS „ xv

PAGE

81. From the perspective of a figure in any given plane, to construct the horizon-

tal projection of the figure 61

82. Change of station, ground and picture planes 61

83. Reflected images 63

84. Shadows 64

85. Heights 66

86. Relations between two perspectives of the same object 67

Chapter III. Perspective Instruments

87. Simplest form of perspective instrument 70

88. Diagraph.. 70

89. Camera lucida. 72

90. Camera obscura 75

91. Perspectograph 77

92. To draw the trace of the principal plane on the drawing board 82

93. To find the distance from the station to a front line of the ground plane. ... 82

94. To find the distance between the two slides 83

95. To draw the graduation for the height of the station 84

96. To draw the horizon, ground and principal lines of the perspective 84

97. Centrolinead 85

98. Perspectometer 88

99. Drawing the ground plan with the camera lucida 89

100. Drawing the ground plan with the camera obscura 90

101. Drawing the ground plan with the perspectograph 91

102. Change of scale ...... 92

Chapter IV. Field Instruments

103. Lenses 94

104. Aberrations 99

105. Diaphragms 103

108. Canadian equipment 139

109. Use of instruments 145

Chapter V. Hurter And Driffield’s Investigations

111. Density, opacity, transparency 147

112. Photometer 150

114. Gradation 159

115. Action of light on the sensitive film 162

116. Speed of plates 167

117. Negatives and positives 171

118. Contact printing and enlarging 175

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Chapter VI. Photographic Operations

PAGE

119. Dry plates 181

Chapter VII. Field Work

123. Triangulation 203

124. Camera stations 205

Chapter VIII. Plotting The Survey

125. Scale of plan 207

126. Plotting the triangulation , 208

127. * Checking the photographs. 209

128. Plotting the traces of the picture and principal planes 210

129. Identification of points 211

130. Plotting the intersections 212

131. Plotting with the perspectograph 213

132. Heights 214

133. Vertical intersections 216

134. Photograph board 216

135. Construction of the traces of a figure’s plane 218

136. Contour lines 219

137. Photograph protractor 221

138. Precision of the method of photographic surveying 223

Chapter IX. Photographs On Inclined Plates

139. General remarks 224

140. Plotting the directions of points of the photographs 224

141. Determination of heights 225

142. Determination of the horizon line and vanishing point of verticals 226

143. Transferring the perspective to a vertical plane 227

144. Photographs on horizontal plates 228

SUPPLEMENTARY NOTE.

Laussedat’s new photo-theodolite.