Basic Photogrammetry

What is Photogrammetry?

• ^{Photogrammetry is the art, science, and technology of obtaining reliable information about physical objects and the environment through processes of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant energy and other phenomena}

• Photogrammetry is the technique, profession, art and science of determining the terrestrial or three-dimensional positions of points and the distances and angles between them

• Photogrammetry is the is a framework for gathering, managing, and analyzing data. Rooted in the science of geography, gis integrates many types of data

• ^{Photogrammetry is the is the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.}

What is Aerial Photogrammetry?

• the scanning of the earth by satellite or high-flying aircraft in order to obtain information about it

• used to describe survey techniques using photographs taken from the air or from space.

• taking photos and combine to make orthophoto

• have the information such as scale and focal length

List two techniques of aerial photogrmmetry:

• Elavation

• Surveying

• Aerial

• Terrestrial

Give two advantages using photogrammetry:

• Covers large area

• Weather dependent

• Easy to interpret and understand

• Costly at the time of installation/initiation

Give two disadvantages using photogrammetry:

• Less time consumtion/ fast

• Can ‘reach’ inaccessable and restricted area

• Heavy and sophisticated equipment needed

• Lengthy administration procedure for getting permission to fly

Type of Aerial Photograph:

• Fiducial Mark

• Oblique

• Vertical

• Camera Axis

State the characteristics of Low Oblique:

• It does not show the horizon

• It covers a very large area

• Relief may be quite discernible but distorted as in any oblique view.

• It covers a relatively small area

State the characteristics of High Oblique:

• No scale is applicable to the entire photograph, and distance cannot be measured.

• The view varies from the very familiar to unfamiliar, depending on the height at which the photograph is taken.

• It covers a very large area

• Relief is discernible but distorted

2 main factors of scale variation

• Cover area

• Variable terrain

• Distance of the principle point

• Tilt of photographs

^{Define to find the Scale of a Vertical Aerial Photograph over Variable Terrain}

• S = f / (H + h)

• S = f * (H - h)

• S = f / (H - h)

• S = f * (H + h)