R.T.U / G.I.T JAIPUR SUBJECT – Surveying (3CE4-05) CIVIL ENGG./ III SEM

UNIT – 4 TACHEOMETRY AND PHOTOGRAMMETRY SURVEYING

1 PRATEEK SHARMA R.T.U / G.I.T JAIPUR SUBJECT – Surveying (3CE4-05) CIVIL ENGG./ III SEM

Blown up Detail 1.1 Introduction 1.2 Instrument used 1.3 Classification of Tacheometry 1.3.1 Stadia Tacheometry 1.3.2 Tangential Tacheometry 1.4 Introduction of Photogrammetry Surveying 1.5 Application of Photogrammetry 1.6 Advantage & Disadvantage 1.7 Principle of Photogrammetry 1.8 Types of Photogrammetry 1.9 Aerial Photographs 1.10 Relief Displacements 1.11 Tilt Displacements 1.12 Flight Planning

2 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM 1.1 Introduction

• Tacheometry is the branch of survey in which the horizontal and vertical distances of points are obtained by instrumental observations such as staff intercepts and angles. – The process of measuring horizontal distance is eliminated

– Less accurate, but more rapid

– Best useful in case of rough & difficult terrain

– Primary objective is preparation of contour maps or plans

– Used in Hydrographic surveys, location surveys etc.

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1.2 Instruments used in Tacheometry are:

Tacheometer – A transit Theodolite fitted with a stadia diaphragm

Diaphragm is the frame upon which is mounted the crosshairs to give a definite line of sight. Stadia hairs / Stadia Lines are a pair of horizontal hairs provided in addition to the regular crosshairs. Each on of this is equidistant from the central horizontal hair. Commonly used Stadia diaphragms are shown here.

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Levelling Staff / Stadia Rod – a scale, shown below, graduated in metres and centimeters. They may be single solid, folding or telescopic.

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Important Terminology

•Stadia Interval (i)– the actual physical distance between the top & bottom stadia hairs •Staff intercept (S) – the difference between the leveling staff readings corresponding to the top & bottom stadia hairs

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1.3 CLASSIFICATION OF TACHEOMETRY – based on the underlying principle 1) Stadia Tacheometry – make use of stadia hairs. Involves observation of either staff intercepts or stadia intervals. a.Fixed Hair method – • Stadia hairs are stationary => Stadia interval (i) is constant • Staff intercept depends upon the horizontal distance between the tacheometer and stadia rod => Staff intercept (S) is variable • Most commonly used b. Movable Hair method – • Here, the stadia rod or leveling staff is provided with two fixed targets. The stadia hairs can be moved to coincide the targets accurately, using micrometer screws => Stadia interval (i) is variable • Since the same staff with fixed targets is used everywhere => Staff intercept (S) is constant • Rarely used 2) Tangential Tacheometry – does not use stadia hairs, hence stadia diaphragm is not required. Here, a transit Theodolite is used to measure vertical angles to the two fixed targets on a staff held at a station point.

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1.3.1 Stadia Tacheometry

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1.3.1 Stadia Tacheometry

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11 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

12 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

13 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

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1.3.2 Tangential Tacheometry

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17 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

PHOTOGRAMMETRY SURVEYING

18 PRATEEK SHARMA 1.4 Introduction of Photogrammetry Surveying

O It is the science of making measurements fromphotographs. O Output of photogrammetry is typically a map,diagram measurement, or a 3D model of some real-world object or scene. O Photogrammetric surveying or photogrammetry is the branch of surveying in which maps are prepared from photo-graphs taken from ground or air stations. O With anadvancement of the photogrammetric techniques, photographs are also being used for the interpretation of geology, classification of soils and crops,etc. O Is the science of making measurements from photographs, especially for recovering the exact positions of surface points. O Used to recover the motion pathways of designated reference points located on any moving object, on its components and in the immediately adjacent environment. O Photogrammetry may employ high-speed imaging and remote sensing in order to detect, measure and record complex 2-D and 3-D motion fields.

Now a days devices– drone camera, aircraft,phototheodolite, digital camera etc. R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

• Photogrammetry is traditionally used to create topographic maps from aerial and spatial imagery. Close range photogrammetry is also used at the School of Surveying to obtain accurate measurements of animals in wildlife research or to create virtual models of historical buildings. • The fundamental principle used by photogrammetry is triangulation. By taking photographs from at least two different locations, so-called “lines of sight” can be developed from each camera to points on the object. • Photogrammetry is used in fields such as topographic mapping, architecture, engineering, manufacturing, quality control, police investigation, cultural heritage, and geology.

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• At 1 part in 30,000 on a 3m object, point positions would be accurate to 0.1mm at 68% probability (one sigma). This is relative accuracy. To find the absolute accuracy the project must be scaled and or have control points defined. Then the accuracy of these scales and control points affect the absolute accuracy. • In 1849, Aimé Laussedat (April 19, 1819 - March 18, 1907) was the first person to use terrestrial photographs for topographic map compilation. He is referred to as the "Father of Photogrammetry".

21 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

• Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena. • Photogrammetry appeared in the middle of the 19th century, almost simultaneously with the appearance of photography itself. The use of photographs to create topographic maps was first proposed by the French surveyor Dominique F. Arago in about 1840. • The term photogrammetry was coined by the Prussian architect Albrecht Meydenbauer, which appeared his 1867 article "Die Photometrographie." • There are many variants of photogrammetry. One example is the extraction of three-dimensional measurements from two-dimensional data (i.e. images); for example, the distance between two points that lie on a plane parallel to the photographic image plane can be determined by measuring their distance on the image, if the scale of the image is known. Another is the extraction of accurate color ranges and values representing such quantities as albedo, specular reflection, metallicity, or ambient occlusion from photographs of materials for the purposes of physically based rendering.

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• Broadly Photogrammetry Requires: • Planning & taking the photographs • Processing the photographs • Measuring the photographs & Reducing • the measurement to produce end results. • Field Application of Photogrammetry : • Used to conduct topographical survey or engineering surveys. • Suitable for mountainous and hilly terrain with little vegetation. • Used for geological mapping which includes identification of land forms, rock type & rock structures. • Used for projects demanding higher accuracy, since it provides • accurate measurements. • Used in urban and regional planning applications. • Used mostly in Planning/designing in transport planning, bridge, • pipeline, hydropower, urban planning, security and strategic • planning, disaster management, natural resources management, city • models, conservation of archaeological sites etc.

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1.5 Application of Photogrammetry

• Importance/application of photogrammetry • Its applications include satellite tracking of the relative positioning alterations in all Earth environments. • The quantitative results of photogrammetry are used to guide and match the results of computational models of the natural systems, thus helping to invalidate or confirm new theories, to design novel vehicles or new methods for predicting or/and controlling the consequences of earthquakes, tsunamis, any weather types. • Photogrammetry also helps for the solving of triangulation, trilateration and multidimensional scaling. • In the simplest example, the distance between two points that lie on a plane parallel to the photographic image plane can be determined by measuring their distance on the image, if the scale (s) of the image is known.

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1.6 Advantage & Disadvantage • Used in different fields, such as topographic mapping, architecture, engineering, manufacturing, quality control, police investigation, and geology, as well as by archaeologists to quickly produce plans of large or complex sites and by meteorologists.

25 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM 1.7 PRINCIPLE OF PHOTOGRAMMETRY

• Principle of photogrammetric survey in its simplest form is very similar to that of the plane table survey. • Only difference is that the most of the work which in plane table survey is executed in the field, but here is done in office. • The principal point of each photograph is used as a fixed station and rays are drawn to get points of intersections very similar to those used in plane table. • Is suitable for topographical or engineering surveys and also for those projects demanding higher accuracy. • It is unsuitable for dense forest & others due to the difficulty of identifying points upon the pair of photographs.

26 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM 1.8 TYPES OF PHOTOGRAMMETRY / PHOTOGRAPHS

• The photographs used in photogrammetry may be broadly classified into two types depending upon the camera position at the time of photography. • The types are- • Terrestrial Photographs • Aerial Photographs • Terrestrial Photographs • Photographs taken from camera station at a fixed position on or near the ground is known as Terrestrial Photographs. • The photographs are taken by means of a photo theodolite which is combination of a camera and a theodolite. • Based on the principle that “if the directions of same objects photographed from two extremities of measured base are known, their position can be located by the intersection of two rays to the same object.

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TERRESTRIAL PHOTOGRAPHS

• Difference between this and plane tabling is that more details are at once obtained from the photographs and their subsequent plotting etc. is done by the office while in plane tabling all the detailing is done in the field itself. • Fig A and B are the two stations at the ends of base AB. • Arrows indicate the directions of horizontal pointing (in plan) of the camera. • For each pair of pictures taken from the two ends, the camera axis is kept parallel to each other. • From economy and speed point of view, minimum number of photographs should be used to cover the whole area and to achieve this, it is essential to select the best positions of the camera stations. • Study of the area should be done from the existing maps, and a ground reconnaissance should be made. Selection of actual stations depends upon the size and ruggedness of the area. These photographs provides the front view of elevation & are generally used for the survey of structure & Architectural Monuments.

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AERIAL PHOTOGRAPHS • Photographs taken from a Aerial camera mounted on a aerial vehicle • Used for various purpose, mainly information extraction on the ground surface • Aerial photographs are obtained from the aerial cameras mounted on aerial vehicle( aeroplane for the purpose of photography) • Used for various purpose, mainly information extraction on the ground surface • Photographs are taken from camera station in the air with the axis of camera vertical or nearly vertical. • Is the branch of photogrammetry where the photographs are taken from air station. • This is the best mapping procedure yet developed for large objects and are useful for military intelligence. • For this, aerial camera is used which are fixed on flying aircraft.

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31 PRATEEK SHARMA R.T.U / G.I.T JAIPUR Surveying (3CE4-05) CIVIL ENGG./ III SEM

AERIAL PHOTOGRAPHS • According to the direction of the camera axis at the time of exposure aerial photographs may be classified into: • Vertical photographs • Oblique photographs • Vertical photographs • These photographs are taken from the air with the axis of the Camera vertical or nearly vertical. • A truly vertical Photograph closely resembles a map. • These are utilized for the compilation of topographic and engineering surveys on various scales.

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OBLIQUE PHOTOGRAPHS • Photographs are taken from air with the axis of the camera intentionally tilted from the vertical. • An oblique photograph covers larger area of the ground but clarity of details diminishes towards the far end of the photograph. • Depending upon the angle of obliquity, oblique photographs may he further divided into two categories. • Low oblique photographs : • An oblique photograph which does not show the horizon, is known as low oblique photograph. • Such photographs are generally used to compile reconnaissance maps of inaccessible areas. • High oblique photograph: • An oblique photograph which is sufficiently tilted to show the horizon, is known as high oblique, photograph. • Such photographs were previously used for the extension of planimetric and height control in areas having scanty ground control.

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1.9 AERIAL PHOTOGRAPH / CAMERA (PU2006) • Aerial camera are used to have aerial photographs which are fixed on flying aircraft. • Primary function of the terrestrial camera as well as the aerial camera is the same, i.e., that of taking pictures. • Aerial camera is mounted on a fast moving aeroplane, its requirements are quite different. • Aerial camera requires : • Fast Lens • High speed & sufficient shutter • High speed emulsion for the film • A Magazine to hold large rolls of film

• Aerial camera is considered to be a surveying instrument of great precision.

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1.10 RELIEF DISPLACEMENT • The scale of an aerial photograph is partly a function of flying height. • Thus, variations in elevation cause variations in scale on aerial photographs. • Specifically, the higher the elevation of an object, the farther the object will be displaced from its actual position away from the principal point of the photograph (the point on the ground surface that is directly below the camera lens). • The lower the elevation of an object, the more it will be displaced toward the principal point. This effect, called relief displacement, is illustrated in the diagram below. • Note that the effect increases with distance from the principal point.

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• Determine an expression for determining the relief displacement on a vertical photograph • Ground relief is shown in perspective on the photograph due to which every point on the photograph is displaced from their true orthographic position. • This Displacement is called relief displacement. • It is denoted by d.

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1.11 TILT DISPLACEMENT

• Defined as the difference between the distance of the image of a point on the tilted photograph from the isocentre and the distance of the image of the same point on the photograph from the isocentre if there had been no tilt. • An error in the position of a point on the photograph due to indeliberate tilting of the aircraft: • Due to instability of aircraft. • May be due to tilting of the aircraft along the flight. • line and/or perpendicular to the flight line. • Increases radially from the isocenter.

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BASIC TERMS USED IN PHOTOGRAMMETRY • Fiducial mark - A fiducial mark is one of two, three or four marks, located in contact with the photographic emulsion in a camera image plane to provide a reference line or lines for the plate measurement of images. • Iso centre - The point in which the bisector of the angle of tilt meets the photographs is known as Isocentre. • It lies on the principal line at a distance of f tan t/2 from the principal point • Principal Point • The point where a perpendicular dropped from the front nodal point strikes the photographs is known as principal point of photograph. • Focal length • It is the perpendicular distance from the centre of the camera lens to either the picture plane or the camera plate. • Tilt : The deviation of a plate from the horizontal plane at the time of exposure is known as tilt. • Horizontal Point (h): The point of intersection of the principal line (VIP) and the horizontal line (oh) through the perspective centre O is known as horizontal point.

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1.12 Flight Planning • A flight planning consists of a flight (navigation) map which shows where the aerial photographs are to be taken and parameters (specifications) which outlines the specific requirements such as aerial camera and film requirements, scale, flying height, end lap, side lap, tilt and swing round (yaw) tolerances, etc. • The flight planning is the first step in photogrammetric project. The main goal of planning is finding out the best fit flight lines and camera exposure stations. In order to cover the project area with minimum number of models, flight lines and camera exposure stations must be planed carefully.

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