introduction of photogrammetry

Photogrammetry IPhotogrammetry I

Introduction to Photogrammetry

S.M.J.S.SamarasingheSuperintendent of Surveys

Institute of Surveying and Mapping

Diyatalawa- Sri Lanka

• Introduction to Photogrammetry: History of the development of Aerial Surveying. The Geometry of the titled photography.

• The characteristics of the Aerial Camera, Auxiliary equipment used in aerial Photography. Photographic mission planning. Understanding aerial photograph (Principle information etc…). Principles of stereoscopic vision, definition of parallax, the basic parallax formula.

• Stereoscopic Viewing methods, Distortions in a field photograph.

Lecture OutlineLecture Outline

Lecture OutlineLecture Outline

•Geometry of stereo pairs, Theory of orientation: Inner orientation, Relative orientation, Absolute orientation. •Problems in relative orientation due to topography.•Photogrammetric plotting Instruments (Analogue). Ground control.•Model Deformation. Numerical Relative Orientation. •Photographic coordinate system. Mono comparator, Stereo comparator measurements of photo coordinates, Transformation. •Elementary methods of planimetric mapping with vertical photographs. Field compilation and map making.

Text BookText Book

Elements of Photogrammetry- Second edition , Author: Paul R. Wolf

ActivitiesActivitiesLecture Hours 30Practical & Tutorial Hours 15

Final Exam 80%Assignments and quizzes 20%

100%

Grade PolicyGrade Policy

EvaluateEvaluate

Introduction

Definitions:

Remote Photogrammetry

”The science or art of obtaining reliable measurements by means of photographs.”

”Photogrammetry is the art, science, and technology of obtaining reliable information about physical objects and the environment through the processes of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant energy and other phenomena.” (ASPRS, 1980)

DefinitionDefinition

Why Photogrammetry………

RAF's wartime reconnaissance photos -archive

Dramatic pictures illustrate Allied assault on D-Day and bombing raids over Germany

Analog PhotogrammetryAnalog PhotogrammetryUsing optical, mechanical and electronical components,

and where the images are hardcopies. Re-creates a 3D model for measurements in 3D space.

Analytical PhotogrammetryAnalytical PhotogrammetryThe 3D modelling is mathematical (not re-created) and

measurements are made in the 2D images.

Digital PhotogrammetryDigital PhotogrammetryAnalytical solutions applied in digital images. Can also

incorporate computer vision and digital image processing techniques.

or Softcopy Photogrammetry”Softcopy” refers to the display of a digital image, as

opposed to a ”hardcopy” (a physical, tangible photo).

Photogrammetry………

Photograph ImageA scene which was detected as well as recorded on film.

A scene which was detected

electronically.

Chemical reactions on a light sensitive film detects the intensity of the incoming energy.

Generate an electrical signal

proportional to the incoming

energy.

Simple, cheap, well known. Can sense in many wavelengths,

data can be easily converted

into digital form for automated

processing.

Only sense in the wavelength of

0.3 – 0.9 μm, manual interpretation.

Complex,

Expensive sensors

Photograph vs. Image

Relationships of the Mapping Sciences as they relate to Mathematics and Logic, and the Physical, Biological, and Social Sciences

History

History of Aerial Photography:

HistoryHistory

HistoryHistory

Origins of Remote Sensing

First photographs taken in 1839

Remote sensing began withaerial photography

HistoryHistory

1858 Gasper Felix Tournachon "Nadar" takes photograph of village of Petit Bicetre in France from

a balloon.

Paris by Nadar, circa 1858

HistoryHistory

Boston by Black and King (1860)

HistoryHistory

World War One was a major impetus to development of aerial photography

HistoryHistory

After the war the technology was in place to begin large scale aerial surveys

A brief history of Photogrammetry

A brief history of Photogrammetry

A brief history of Photogrammetry

Why Photogrammetry………

Measuring values and camera constants

Why Photogrammetry

•Extracting geometrical information and producing maps.

•Cheaper than terrestrial methods.

•Extracting qualitative information.

•High speed of map generation.

Why Photogrammetry………

Ideal technology when measuring objects such as

– Vast regions to be mapped – Irregular shapes and

– Objects that are too • Hot or cold • Soft • Delicate • Inaccessible • Toxic • Radioactive to touch

Photogrammetric products

Planimetric maps –

Planimetric elements in geography are those features that are independent of elevation, such as roads, building footprints, and rivers and lakes. They are represented on two-dimensional maps as they are seen from the air, or in aerial photography. These features are often digitized from orthorectified aerial photography into data layers that can be used in analysis and cartographic outputs.

Topographic maps –

A type of map characterized by large-scale detail and quantitative representation of relief, using contour lines. Traditional definitions require a topographic map to show both natural and man-made features. A topographic map is typically published as a map series.

Photogrammetric products……

3D points

LiDAR has become the technology of choice for deriving highly accurate terrain data and 3D models, and it is commonly used for a variety of mapping applications.

Photogrammetric products……

Photomap (Orthophotos)

DEM/ DTM

DSM

General Process

General Flow

Real World(Earth)

Sensor (Camera)

Data Source(Images)

Image Refinement& measurement

Refined Image

Observation

Products•Maps•DEM

•Otrthophoto

Mathematical Models

Decision Making

Data Analysis

Production Line Mapping Using Aerial Photogrammetry Production Line Mapping Using Aerial Photogrammetry

Photogrammetric Types

Photogrammetric Types from Applications Point of View (d is distance from camera to object)

Close Range Photogrammetry d<10 m

Terrestrial Photogrammetry 10 m<d<100 m

Aerial Photogrammetry 2 km<d<10 km

Space Photogrammetry 30 km<d

Photogrammetric Types

Close Range Photogrammetry

Terrestrial Photogrammetry

Taken with ground-based cameras

Position and orientation often measured

Terrestrial Photogrammetry

Aerial Photogrammetry

Space Photogrammetry

Extraterrestrial pictures taken from space-based cameras

Extraterrestrial

Spot Image

Space Photogrammetry

Space Photogrammetry

Extraterrestrial

NOAA Image

Extraterrestrial

Ikonos Image

Space Photogrammetry

Types of Images

• Panchromatic, Black & White, Grayscale

• Color RGB

• Multispectral

• Hyperspectral

Panchromatic Image

Black and white Image

Grayscale Image

True Color composite image

False Color composite image

Types of photographs (categorized by tilt)

• Vertical - camera axis as nearly vertical as Possible

• Oblique - camera axis intentionally tilted• Low Oblique• High Oblique

Types of photographs

TerrestrialAerial

Vertical

Oblique

Truly Vertical

Tilted

(1deg< angle < 3deg)

High oblique

(includes horizon)

Low oblique

(does not include horizon)

Vertical Aerial Photogrammetry

Mainly used for mapping

Low Oblique

Low oblique (no horizon)

High Oblique

• Horizon line in the photo

Vertical aerial images are not map!

• Maps are based on parallel projection while photo has central projection

• Maps have a unique scale while image scale varies depending on terrain relief

• Maps are interpreted while photos should be interpreted

• Photo is detailed while maps are generalized

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Projection systems

Taking photographs

Taking Vertical Aerial Photographs

• Photos taken in parallel flight strips

Taking Vertical Aerial Photographs

• Each successive photograph overlap previous photo

Forward Overlap (End Lap)

Aerial Photography Stereo pair

•Over lap about 60%

Aerial Photography – Stereo pair

•Over lap about 60%

•Aerial Base: the distance between two successive projection centers

Side Overlap (Side Lap)

Taking Vertical Aerial Photographs

• Position of camera at each exposure called exposure station

• Flying height – altitude of camera• Adjacent flight strips overlap – side

overlap• Block of photos – photos of 2 or more side

lapping strips

Block of photographs

Projection Plotters

MULTIPLEX MODEL SKETCH

Direct Optical Projection Stereo plottersDirect Optical Projection Stereo plotters

Nistri Photomultiplex

Model D III

Kelsh Stereoplotter

Direct Optical Projection Stereo plottersDirect Optical Projection Stereo plotters

Kern PG-2 analog stereo-plotter.

Direct Optical Projection Stereo plottersDirect Optical Projection Stereo plotters

Kern PG-3 analog stereo-plotter, Switzerland

Direct Optical Projection Stereo plottersDirect Optical Projection Stereo plotters

Wild A-10 analog stereo-plotter.

Direct Optical Projection Stereo plottersDirect Optical Projection Stereo plotters

Digital systems require that the aerial photographs be scanned as high-resolution images.

Digital systemsDigital systems

END