Introduction to Remote Sensing

Presentation on theme: "Introduction to Remote Sensing"— Presentation transcript:

1 Introduction to Remote Sensing

2 Outline Remote Sensing Defined Electromagnetic Energy (EMR) Resolution
Interpretation

3 Remote Sensing Defined
Remote Sensing is: “The art and science of obtaining information about an object without being in direct contact with the object” (Jensen 2000). There is a medium of transmission involved. Information usually gathered from spacecraft or an airplane, but can be a handheld or boom-mounted device. Originally defined in 1960’s according to Jensen, to encompass photogrammertry and information gathered from nonphotometric sources. 3

4 Remote Sensing Defined
… the collection of information about Earth surfaces and phenomena using sensors not in physical contact with the surfaces and phenomena of interest. We will focus on data collected from an overhead perspective via transmission of electromagnetic radiation.

5 Remote Sensing Defined
Remote Sensing Includes: A) The mission plan and choice of sensors; B) The reception, recording, and processing of the signal data; and C) The analysis of the resultant data.

6

7 Electromagnetic Spectrum
The sun is the prime source of electromagnetic radiation on the earth’s surface, which is primarily shortwave radiation, and the earth transmits back longwave radiation.

8

9

10

11 Resolution All remote sensing systems have four types of resolution:
Spatial Spectral Temporal Radiometric

12 Resolution

13 Resolution

14 Spatial Resolution High vs. Low?

15 Resolution

16 Resolution

17 Spectral Resolution

18 Resolution

19 Radiometric Resolution
6-bit range 63 8-bit range 255 10-bit range 1023

20 Resolution

21 Temporal Resolution Time July 2 July 18 August 3 July 1 July 12
16 days Time 11 days July 1 July 12 July 23 August 3

22 22

23 Aerial Photos Balloon photography (1858) Pigeon cameras (1903)
Kite photography (1890) Aircraft (WWI and WWII) Space (1947) Nader (Gaspard Felix Tournachon) 1858 Paris photographer went up in balloons. Also used during American Civil War. Arthur Batut, French Kite photographer published book in 1890 Julius Neubronner patented breast mounted cameras on pigeons (1903) Photo reconnaissance in WWI for mapping terrain and troop movements WWII troop movements, V-2 rocket facilities Images: Jensen (2000)

24 Word War I: Air photos for reconnaisance from fighter planes and pigeons Balloons and kites were easy to shoot down, but pigeons were not. Small light weight cameras were attached to the birds and a timer was set to take pictures ever 30 seconds as it flew

25 Oblique photos from mountain peaks: Banff

26 Photogrammetry:       "the science of obtaining reliable measurements from photos"
Photo interpretation: "the identification and extraction of meaning of objects" Photogrammetry needs a minimum 5 known point locations per photo

27 Elements of Image Interpretation
Shape: Many natural and human-made features have unique shapes. Often used are adjectives like linear, curvilinear, circular, elliptical, radial, square, rectangular, triangular, hexagonal, star, elongated, and amorphous.

28 Shape: the form of an object on an air photo helps to identify the object. Regular uniform shapes often indicate a human involvement;

29

30 Size: a measure of the object's surface area
(e.g. single-lane vs. multi-lane highways); Time: temporal characteristics of a series of photographs can be helpful in determining the historical change of an area (e.g. looking at a series of photos of a city taken in different years can help determine the growth of suburban neighbourhoods;

31 Pattern: Pattern is the spatial arrangement of objects on the landscape. General descriptions include random and systematic; natural and human-made. More specific descriptions include circular, oval, curvilinear, linear, radiating, rectangular, etc.

32 Pattern: similar to shape, the spatial arrangement of objects (e. g
Pattern: similar to shape, the spatial arrangement of objects (e.g. row crops vs. pasture) is also useful to identify an object and its usage;

33 Pattern Jensen (2000)

34 Elements of Image Interpretation
Shadow: Shadow reduction is of concern in remote sensing because shadows tend to obscure objects that might otherwise be detected. However, the shadow cast by an object may be the only real clue to its identity. Shadows can also provide information on the height of an object either qualitatively or quantitatively.

35 Shadow Jensen (2000)

36 Shadow: a shadow provides information about the object's height, shape, and orientation (e.g. tree species);

37 Elements of Image Interpretation
Tone and Color: A band of EMR recorded by a remote sensing instrument can be displayed on an image in shades of gray ranging from black to white. These shades are called “tones”, and can be qualitatively referred to as dark, light, or intermediate (humans can see tones). Tone is related to the amount of light reflected from the scene in a specific wavelength interval (band).

38 Tone/Colour: the colour characteristics of an object, relative to other objects in the photo (e.g. sand has a bright tone, while water usually has a dark tone; tree species can be determined by the colour of their leaves at certain times of the year); Monochrome (panchromatic) air photos are used more frequently as colour  photography costs twice as much.

39 Tone and Color Jensen (2000)

40 Elements of Image Interpretation
Texture: Texture refers to the arrangement of tone or color in an image. Useful because Earth features that exhibit similar tones often exhibit different textures. Adjectives include smooth (uniform, homogeneous), intermediate, and rough (coarse, heterogeneous).

41 Texture Jensen (2000)

42 Texture: the physical characteristics of an object affect texture
(e.g. calm water has a smooth texture; a forest canopy has a rough texture);

43 Elements of Image Interpretation
Height and Depth: As discussed, shadows can often offer clues to the height of objects. In turn, relative heights can be used to interpret objects. In a similar fashion, relative depths can often be interpreted. Descriptions include tall, intermediate, and short; deep, intermediate, and shallow.

44 Height and Depth

45 Elements of Image Interpretation
Association: This is very important when trying to interpret an object or activity. Association refers to the fact that certain features and activities are almost always related to the presence of certain other features and activities.

46 Association/Site: associating the presence of one object with another, or relating it to its environment, can help identify the object (e.g. industrial buildings often have access to railway sidings;

47 Association Jensen (2000)

48

49

50

51 Thank You 51