Introduction of photogrammetry

PPhhoottooggrraammmmeettrryy II
Introduction to Photogrammetry
S.M.J.S.Samarasinghe
Superintendent of Surveys
Institute of Surveying and Mapping
Diyatalawa- Sri Lanka

LLeeccttuurree OOuuttlliinnee
• 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.

LLeeccttuurree OOuuttlliinnee
•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.

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

AAccttiivviittiieess
Lecture Hours 30
Practical & Tutorial Hours 15
Final Exam 80%
Assignments and quizzes 20%
100%
GGrraaddee PPoolliiccyy
EEvvaalluuaattee

Definitions:
DDeeffiinniittiioonn
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)

Why Photogrammetry………
RAF's wartime reconnaissance
photos -archive
Dramatic pictures illustrate Allied assault on
D-Day and bombing raids over Germany

Photogrammetry………
Analog PPhhoottooggrraammmmeettrryy
Using optical, mechanical and electronical components, and
where the images are hardcopies. Re-creates a 3D model
for measurements in 3D space.
AAnnaallyyttiiccaall PPhhoottooggrraammmmeettrryy
The 3D modelling is mathematical (not re-created) and
measurements are made in the 2D images.
DDiiggiittaall PPhhoottooggrraammmmeettrryy
Analytical 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).

Photograph Image
A 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

HHiissttoorryy
History of Aerial Photography:

HHiissttoorryy
Origins of Remote Sensing
Remote sensing began with
aerial photography
First photographs taken in
1839

HHiissttoorryy
Paris by Nadar, circa
1858
1858 Gasper Felix Tournachon "Nadar" takes
photograph of village of Petit Bicetre in France from
a balloon.

HHiissttoorryy
Boston by Black and King (1860)

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

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

A brief history of 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.

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 Flow
Real World
(Earth)
Sensor
(Camera)
Data Source
(Images)
Image Refinement
& measurement
Refined
Image
Observation
Products
•Maps
•DEM
•Otrthophoto
Mathematica
l Models
Decision
Making
Data
Analysis

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

Terrestrial Photogrammetry
 Taken with
ground-based
cameras
 Position and
orientation often
measured

Space Photogrammetry
 Extraterrestrial pictures taken from space-based
cameras

 Extraterrestrial
Spot Image

NOAA Image

Ikonos Image

Types of Images
• Panchromatic, Black & White, Grayscale
• Color RGB
• Multispectral
• Hyperspectral

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
Aerial Terrestrial
Vertical
Oblique
Truly Vertical
High oblique
(includes horizon)
Tilted
(1deg< angle < 3deg)
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

Taking Vertical Aerial Photographs
• Photos taken in parallel flight strips

• Each successive photograph overlap previous
photo

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

• 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

Direct Optical PPrroojjeeccttiioonn SStteerreeoo ppllootttteerrss
 MULTIPLEX MODEL SKETCH

 Nistri Photomultiplex
Model D III
 Kelsh Stereoplotter

 Kern PG-2 analog stereo-plotter.

 Kern PG-3 analog stereo-plotter, Switzerland

 Wild A-10 analog stereo-plotter.

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

Introduction of photogrammetry

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