Outline Remote Sensing Defined Resolution Electromagnetic Energy (EMR) Types Interpretation Applications

Transcription

1 Introduction to Remote Sensing

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

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.

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5 Remote Sensing Defined Remote Sensing: 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.

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7 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.

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10 Remote Sensing Process Components Energy Source or Illumination (A) Radiation and the Atmosphere (B) Interaction with the Target (C) Recording of Energy by the Sensor (D) Transmission, Reception, and Processing (E) Interpretation and Analysis (F) Application (G)

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

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15 Spatial Resolution High vs. Low?

16 Spectral Resolution

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

18 Radiometric Resolution 6-bit range bit range bit range

19 Electromagnetic Spectrum

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22 Aerial Photos Balloon photography (1858) Pigeon cameras (1903) Kite photography (1890) Aircraft (WWI and WWII) Space (1947) Images: Jensen (2000)

23 Early days: Boston, from Tethered Balloon (1860) Development of air photography before airplanes

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 Early topographic mapping from mountain peaks: Canadian Rockies, 1890 Photo-topography topography led by Edouard Deville

27 Since 1945, all our topographic mapping is done from aerial photography: Air photos enabled a huge reduction in fieldwork costs, and an increase in how quickly and accurately large areas could be mapped Athabasca Glacier, 1958

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

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30 Anaglyphs 3D imagery

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

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

36 Shape Jensen (2000)

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38 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;

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

40 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;

41 Pattern Jensen (2000)

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43 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.

44 Shadow Jensen (2000)

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

46 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).

47 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.

48 Jensen (2000) Tone and Color

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50 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).

51 Texture Jensen (2000)

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

55 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.

56 Height and Depth

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58 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.

59 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;

60 Association Jensen (2000)

61 Stereo 3D to create elevations

62 Once corrected, and georeferenced, photos can be used for topographic mapping and as a mapping layer, with map data overlain on top. A photograph that has been corrected and is 'planimetrically correct' is known as an orthophoto (e.g. as in google maps or imap ).

63 Google Earth: aerial photography and satellite images

64 Provincial photography is generally redone about every 10 years City photography more frequently: 3-5 years PG 2006

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66 PG 1997

67 Image interpretation