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2 Photogrammetry, GIS & Remote Sensing Quick Reference Book i

3 EDUCREATION PUBLISHING Shubham Vihar, Mangla, Bilaspur, Chhattisgarh Website: Copyright, 2017, S.S. Manugula, V. Bommakanti All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form by any means, electronic, mechanical, magnetic, optical, chemical, manual, photocopying, recording or otherwise, without the prior written consent of its writer. ISBN: Price: ` The opinions/ contents expressed in this book are solely of the authors and do not represent the opinions/ standings/ thoughts of Educreation or the Editors. The book is released by using the services of self-publishing house. Printed in India ii

4 Photogrammetry, GIS & Remote Sensing Quick Reference Book Dr. S.S. Manugula Dr. Veeranna Bommakanti EDUCREATION PUBLISHING (Since 2011) iii

5 Preface This book has been written for use in classrooms by both the instructor and the students and also for independent study in the coming decades. The main intention for writing this book is to make the subject very easy at the same time to cover the syllabus for undergraduate students. The basic concepts of Photogrammetry, Remote Sensing & GIS all are included in a single book which helps the students to the face the exams easily and very quickly. This book is intended to be basically utilized as a quick reference in support to various text books. This book also covers few real images which I used in the industries during my visit to UAE (Dubai & Abu Dhabi) for set up a project for Military Survey Department. Dr. S.S. Manugula Dr. Veeranna Bommakanti iv

6 Content List Sr. Content Page 1. Introduction to Photogrammetry Types of Photogrammetry Principle and types of aerial photographs, Geometry of vertical aerial photograph, Scale and Height measurement on single vertical aerial photograph, Height measurement based on relief displacement, Fundamental of stereoscopy, fiducial points, parallax measurement using fiducial line. 2. Remote Sensing Basic concepts of Remote Sensing, Data and Information, Remote sensing data collection, Remote sensing advantages & Limitations, Remote sensing process. Electro-magnetic Spectrum, Energy interactions with atmosphere and earth surface features (soil, water, vegetation), Indian satellite and sensors Characteristics, Resolution, Map and Image and False color composite, introduction to digital data analysis. Elements of visual interpretation techniques. 3. Geographic Information System Introduction to GIS, Components of GIS, Geospatial Data- Spatial Data, and Attribute data-joining Spatial and Attribute data: GIS Operation: v

7 Spatial Data Input-Attribute data Management.-Data display- Data Exploration-Data Analysis. COORDINATE SYSTEMS: Geographic Coordinate System: Approximation of Earth, Datum; Map Projections: Types of Map Projection Map projection parameters-commonly used Map projections-projected coordinate System. 4. Vector Data Model Representation of simple features- Topology and its importance; coverage and its importance: coverage and its data structure, Shape file; Data models for composite features Object Based Vector Data Model; Classes and their Relationship; The geo database data model; Geometric representation of Spatial Features and data structure, Topology rules 5. Raster Data Model Elements of the Raster data model, Types of Raster Data, Raster Data Structure, Data Conversion, Integration of Raster and Vector Data. Data Input: Metadata, Conversion of Existing data, creating new data; Remote Sensing data, Field data, Text data, Digitizing, Scanning, on screen digitizing, importance of source map, Data Editing. 6. UNIVERSITY QUESTION BANK (UQB) vi

8 Photogrammetry, GIS & Remote Sensing Chapter 1 Introduction to Photogrammetry Introduction Photogrammetry is a Branch of Remote Sensing. Defined as the art, science, and technology of obtaining reliable information about physical objects and the environment. This is done through a process of recording, measuring, and interpreting aerial and terrestrial photographs. In a sense, the word photogrammetry may be analyzed in two parts: photo- meaning picture," and grammetry - meaning "measurement." Therefore; photo-measurement. Types of Photogrammetry Photogrammetry was invented in 1851 by laussedat, and has continued to develop over the last 140 years. Over time the development of photogrammetry has passed through the phases of 1. Plane table photogrammetry 2. Analog photogrammetry 3. Analytical photogrammetry 4. Digital photogrammetry (latest) 1

9 Dr. S.S. Manugula, Dr. Veeranna Bommakanti The traditional, and large, application of photogrammetry is to extract topographic information (e.g., topographic maps) from aerial images. However, photogrammetric techniques have also be applied to process satellite images and close range images in order to acquire topographic or non-topographic information of photographed objects. 1. Plane table photogrammetry: Prior to invention of airplane, photographs taken on the ground where used to extract the relationships between objects using geometric principles. This was during the phase of table photogrammetry 2. Analog photogrammetry: In analog photogrammetry, starting with stereo measurement in 1901, optical or mechanical instruments were used to reconstruct three-dimensional geometry from two overlapping photographs. The main product during this phase was topographic maps. 3. Analytical photogrammetry: In Analytical photogrammetry, the computer replaces some expensive optical & mechanical components. The resulting devices were analog/digital hybrids. Analytical aero triangulation, analytical plotters, orthophoto projectors were the main developments during this phase. Outputs of analytical photogrammetry can be topographic maps, but also can be digital products, such as digital maps and DEMs. 4. Digital photogrammetry (latest): Digital photogrammetry is photogrammetry as applied to digital images that are stored and processed by the computer. The images can be obtained by scanning the photographs or by directly from digital cameras. Many photogrammetry tasks can be highly automated in digital photogrammetry (e.g., automated DEM extraction and digital orthophoto generation). Digital photogrammetry can also be called softcopy photogrammetry. 2

10 Photogrammetry, GIS & Remote Sensing The output of the product is in the digital form, such as digital maps, DEMs, and digital Orthophotos saved on the computer media. With the development of digital photogrammetry the photogrammetric techniques are more closely integrated into Remote Sensing and GIS. Principle The principle involved in the aerial photography is The taking of photographs of a regular intervals from an aero plane/satellite along a define line at the certain height above the mean sea level at a specified speed of movement. Further Explanation: -- Photographs are taken from aero planes and satellites with metric and Non-metric cameras. These photographs are collected with forward overlap between each photograph as they are captured down a flight line. Mapping areas may require multiple flight lines in order to include all necessary mapping area within the imagery. In these cases, the imagery flight lines are flown so that they overlap (side lap). Near 3

11 Dr. S.S. Manugula, Dr. Veeranna Bommakanti vertical aerial photography is flown with a forward lap of 60 percent and side lap of 30 percent. Based on the various input parameters and after generating Aero Triangulation (AT) the compiler able to see stereo and map the required features. Planimetric and topographic features are collected from natural colour near vertical aerial photography. Planimetric and topographic mapping is generally the base mapping data set in a GIS or engineering data set. The accuracy of computations and queries made from these base mapping data sets is based on their thoroughness and accuracy. Colour aerial photography provides the clarity and spatial resolution required to achieve most large- and small-scale mapping accuracies. Types of Aerial Photographs The axis of camera may not be remaining exactly vertical. So the aerial photographs are classified into 4 major types. They are 1) Aerial/Vertical photographs 2) Near vertical photographs 3) Tilted photographs 4) Horizontal/terrestrial photographs 1) Vertical Photographs: The photographs taken from an aero plane with camera axis coincide with the direction of gravity are called Vertical Photographs. These photographs are commonly used for topographic mapping and planimetric mapping. 2) Near vertical photographs: The photographs taken from an aero plane with camera axis makes an angle between 1degree and 3 degree from the direction of gravity. For all practical purposes, 4

12 Photogrammetry, GIS & Remote Sensing these photographs are considered as vertical photographs. 3) Tilted / oblique photographs: oblique photographs and images are similar to aerial photographs and images, except the camera axis is intentionally inclined at an angle with the vertical. This can be further divided into Low oblique (camera 30º) and High oblique (camera 60º) from the vertical. These are commonly used for reconnaissance and corridor mapping applications. 4) Horizontal or Terrestrial photographs: Terrestrial or ground-based photographs and images are taken with the camera stationed on or closed to the Earth s surface. These are commonly used for applications involved with archeology, geomorphology, civil engineering, architecture, industry, etc. Geometry of Vertical Aerial Photograph Geometry of the single aerial photograph The geometry of a single vertical aerial photograph is illustrated in Figure 1. In a vertical aerial photograph the optical axis of the camera is vertical and the plane of the photograph (film) is horizontal. The point where the optical axis intersects the photograph is termed the centre point or principal point of the photograph. This can be located on an aerial photograph as the intersection of lines drawn between opposite fiducial marks in the margins of the print. In a perfectly vertical 5

13 Dr. S.S. Manugula, Dr. Veeranna Bommakanti aerial photograph the principal point also represents the plumb point or nadir point which is the photographic position representing the point on the earth's surface vertically beneath the camera lens at the time of exposure. In practice a vertical aerial photograph is rarely absolutely vertical and the nadir point and the centre point do not coincide exactly, the usually small difference being the result of tilt. The distance between the camera lens and the ground represents the flight height of the aircraft and the focal length is the distance between the camera lens and the film. The scale & Height measurement on a single vertical aerial photograph Scale: the ratio of the distance between two points on a photo to the actual distance between the same two points on the ground (i.e. 1 unit on the photo equals "x" units on the ground). If a 1 km stretch of highway covers 4 cm on an air photo, the scale is calculated as follows: Large Scale - Larger-scale photos (e.g. 1:25 000) cover small areas in greater detail. A large scale photo simply means that ground features are at a larger, more detailed size. The area of ground coverage that is seen on the photo is less than at smaller scales. Small Scale - Smaller-scale photos (e.g. 1:50 000) cover large areas in less detail. A small scale photo simply means that ground features are at a smaller, less detailed size. The area of ground 6

14 Photogrammetry, GIS & Remote Sensing coverage that is seen on the photo is greater than at larger scales. Another method used to determine the scale of a photo is to find the ratio between the camera's focal length and the plane's altitude above the ground being photographed f = focal length 6 or mm is common H = height of plane above ground h = height (elevation) of ground H = height of place above datum [altimeter reading (2% error)] One of the most significant geometric relationships is that the angles are subtended at a camera lense by an object and by its photographic image. In other words the triangles abc and cde are similar and it follows that the ratio of object size (O) to image size(i) is the same as the ratio of focal length (f) to flight height (H), or The ratio of image to object size is the general scale of the aerial photograph and it follows that the scale may be determined if the camera focal length and the flight height are known: It is also very important to remember that the flight height refers to a distance above the ground directly 7

15 Dr. S.S. Manugula, Dr. Veeranna Bommakanti below and not necessarily to the attitude (height above sea level or the base airport) of the aircraft. For this reason a more precise restatement of equation 2 should modify as Heights Measurement In a vertical aerial photograph the displacement of images is in a radial direction from the center point of the photograph. This displacement is termed the radial displacement due to relief and represents an error in map positioning For any one aerial photograph the amount of radial displacement, m of the top of an object from its base can be determined by the relation In which r= radial distance on the photograph from the center point to the top of the image displaced, h= height of the object displaced, and H = flight height. Rearranging the equation (4) yields a convenient expression for estimation the height of an object on a photograph by measuring its redial displacement. 8

16 Photogrammetry, GIS & Remote Sensing Fundamental of stereoscopy What is a Stereoscopy? Stereoscopy is the science and art that deals with the use of binocular vision for the observation of overlapping photographs or other perspective views and the method by which such views are produced. - Essentially most of us with normal eyesight have stereoscopic vision (i.e. the ability to see and appreciate depth of field through the perception of parallax.) The stereoscopic methods present two different offset images separately to the left and right eye of the viewer. These two images when combined the brain have the capability to give the perception of 3D depth. Based on the stereo vision i.e. 3D perception one can get and extract more information from the stereo images. Proper Use of Stereoscopes The following are some guidelines that will help you use your stereoscopes properly. They are important and should be kept in mind when performing stereo based interpretations: 1. Be sure that the photos are properly aligned, preferably with the shadows toward the viewer. 9

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