This document discusses aerial photography and how to determine flight direction from aerial photographs. It begins by defining aerial photography and noting that quality is determined by factors like the camera lens and material. Aerial photographs are classified by camera orientation and focal length. Annotations on photographs like fiducial marks, principal points, and X/Y coordinates are used to determine flight direction by finding matching or conjugate points between overlapping photographs. Careful planning of factors like scale, camera format, and overlap is needed to acquire the photographs and cover the study area.

1. DETERMINATION OF FLIGHT
DIRECTION

2. INTRODUCTION
• The term “Photography” is derived from two Greek words
meaning “phos”(light) and “graphien” (writing)
• Photography is the production of permanent images by
means of action of the light
• Aerial Photography is broadly defined as any photographs
of that takes place from an elevated position.

3. MANY FACTORS DETERMINE
THE QUALITY OF AERIAL
PHOTOGRAPHY
Quality of the lens system
 Manufacturing the camera
 Photographic material
 Weather conditions and sun angel during photo flight

4. CLASSIFICATION OF
AERIAL PHOTOGRAPH
• Aerial photographs are usually classified according
to the orientation of the camera axis, the focal
length of the camera
• There are 3 types
* Horizontal photography
* Vertical photography
*Oblique photography

5. ANNOTATIONS
• Fiducial marks
* these are the marks built into aerial
cameras which appear on the sides or in the
corners of the photo
* these are used to determine the precise
location of the principal point

7. • Fiducial axes
The lines joining the opposite fiducial marks on a
photograph are called fiducial axes.
• Principal point
It is a point on the aerial photograph, where a
perpendicular from the interior perspective centre of the
camera lens meets the plane of the aerial photograph
The principal point is the geometric centre of the
photograph

8. • XY co-ordinate:
they are obtained by joining opposite fiducial imaginary
X co-ordinate and Y co-ordinates.
• Perspective centre:
It is the centre point of the lens in camera.
• Flight line:
Photographs are taken with the frame of the cameras
along one line. These lines are called flight line.

10. CONJUGATE PRINCIPAL
POINT
It is a principle point of an aerial photo represented on an
adjacent aerial photograph.

11. NADIR POINT
Nadir point is the point in which a vertical line
through the perspective centre of the camera
lens pierces the plane of the aerial photograph.

12. PHOTO-BASE
• The airbase is called the photo-base on an aerial
photograph and represents the length of the air-base on a
photograph.
In practice it is measurable distance between the
principal point and the conjugate point

13. PREPARATION OF FLIGHT TO
ACQUIRE AERIAL
PHOTOGRAPHS
• process begins with selecting an image scale, camera lens
and format size, and desired image overlap.
• flight planner can then determine such geometric factors
as the appropriate flying height, the distance between
image centres, the direction and spacing of flight line, and
the number of images required to cover the study area.
• Based on these factors, a flight maps are prepared for the
firm providing the photographic services.

14. DETERMINATION OF FLIGHT
DIRECTION

17. PROCEDURE
• Demarcate the boundary of stereopair.
• Demarcate the symbols like fiducial marks, scale etc.
• Join opposite fiducial marks to get co-ordinates.
• X and Y co-ordinates meet the centre and meeting poin
called principal point.

18. • Principal point of first photograph will be present on
second photograph called conjugate principal point.
• Maximum number of points will be present due to 40% -
60% overlap.
• By finding or tracing common points, we can determine
the flight direction.

19. CONCLUSION
Before the aerial photographs came into practice
for analytical and computational work, similar
data collection for topographical surveys and
geological investigations used to be various
photogrammetric and photo-interpretation
techniques, the same work is being carried out
more precisely with economy of time, money
and efforts.

20. THANK YOU