More Remote Sensing Today- - announcements - Review of few concepts - Measurements from imagery - Satellites and Scanners

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Announcements ► Should read chapter 6 for Thursday. Not on Syllabus! ► Bring rulers to class on Thursday… if you got one.

Last lecture we talked about… ► Remote sensing ► Map interpretation ► Geographical data acquisition, management, and analysis ► Introduction to Geographic Information Systems ► Map production

Remote Sensing ► …is the gathering of information by means of a sensor that is not in contact with the object being detected.

Nature of EM radiation

Atmospheric windows

Remote Sensing ► Types of sensors  Active  Passive

Remote Sensing ► See page 254 in Campbell  Film ► Panchromatic ► Color ► False Color IR  Sensors ► Narrow-band ► Multispectral devices

Remote Sensing ► How the image is taken..  Vertical  High-oblique (with horizon)  Low-oblique (without horizon)

Remote Sensing ► vertical

Remote Sensing ► oblique

Remote Sensing ► oblique

Remote Sensing ► Why use obliques??

Remote Sensing ► Why use obliques??

Remote Sensing ► Summary of a few things…  Remote sensing instruments can be divided in many different ways… ► Active / passive ► Film / sensor ► Narrow band / multispectral ► Angle of photo / scan

Remote Sensing ► Aerial Photos…  how they are made… p. 258  Planimetric Shift… p. 260

OK, so… some new stuff… ► Scale…..  Large and small

Scale ► Large scale is local ► Small scale is global

Scale ► Word scales ► Representative fraction ► Graphic

Scale ► 1:24,000 topos ► Brits do word scale.. 1 inch represents one mile A.K.A. 1 : 63,360

Graphic scale

Finding scale on an image ► Find something on photo with a known size ► Compare to a map or other photo with a known scale.

Measuring stuff on an image - Photogrammetry - ► Linear  Dimensional analysis

Measuring stuff on an image - Photogrammetry - ► Linear  Dimensional analysis ► Area

Measuring stuff on an image - Photogrammetry - ► But what if they are squiggly features??? ► Linear  Dimensional analysis ► Area

Measuring stuff on an image - Photogrammetry - ► Linear  Dimensional analysis ► Area ► Height  Shadows  Planimetric shift

See photo in Remote Sensing book ► Video projector

Measuring stuff on an image - Photogrammetry – ► What about the effects of mountains and terrain on measurements?? ► Linear  Dimensional analysis ► Area ► Height  Shadows  Planimetric shift

Scanners and satellite imagery ► How scanners work…. As opposed to photos ► Pixels ► Often 256 values 0 – 255 levels of detection ► Multispectral  Bands covered… 3 in visible, near IR and Far IR  Also radar and microwave (active systems)

► A brief history of satellites ► 1972 Landsat.  1-4 no longer work, 6 bit it. 5 and 7 still working  Cover same spot on earth about every 16 days  “Whisk broom scanner”  Multispectral scanner and thematic mapper Start here….. Scanners and satellite imagery

Scanners and satellite imagery ► Multispectral scanner  79 by 79 resolution  See page 272 (top) for bands covered

► The MSS can simulate rather crude spectral signatures. Bands 4, 5, and 6 each have a bandwidth of 0.1 µm; and band 7's width is 0.3 µm. We represent band responses by bars in a histogram-like plot, in which the height of the bar signifies the relative reflectances averaged for all wavelengths within the bandwidth interval.. From…

From /remotesens/iraq.php. Landsat image: MSS Bands 4, 2 and 1, taken on 16 February 1973, 14 February 1975 and 27 May /remotesens/iraq.php /remotesens/iraq.php

Scanners and satellite imagery ► Multispectral scanner  79 by 79 resolution  See page 272 (top) for bands covered ► thematic mapper  30 x 30 resolution (thermal – 120 or 60)  See page 273 for bands covered

Scanners and satellite imagery ► Resolution  Object needs to be 2x resolution to be seen (reliably)

► From ch/proser/remotesens/ iraq.php. Landsat image: ETM Bands 4, 3 and 2, taken on 26 March and 4 May ch/proser/remotesens/ iraq.php ch/proser/remotesens/ iraq.php

Atmospheric windows

► TM image ► Bands 2, 3, 4 ► Displayed blue, green, red

► 25-Meter MultispectraL, Landsat TM, Bands 7,4,3 (RGB), Acquired February 13, In this image of Hong Kong, vegetation appears in green, bare soil is reddish purple, and urban features are purple and white. This particular band combination easily distinguishes water/land boundaries because water bodies (shown in black) contrast strongly with colorful land features. ► From gov/images/gallery.html

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Scanners and satellite imagery ► SPOT  ‘push-broom’ scanner  3 visible and near IR  20 meter multispect and 10 meter single  Fly-over same spot each 20 days (apx)  Can be pointed away from vertical. Uses? ► Stereopairs, more frequent observations

Scanners and satellite imagery ► IKONOS  1 meter (page 274 in book) ► Active  Radar and microwave ► Military  ??????

Scanners and satellite imagery ► Contrast stretching and edge enhancement (page. 276)

To Summarize……

Remote Sensing ► Summary of a few things…  Remote sensing instruments can be divided in many different ways… ► Active / passive ► Film / sensor ► Narrow band / multispectral ► Angle of photo / scan

Photogrammetry ► Summary  Scale  Measurements, linear, area, height  Dimensional analysis  Effects of topography

Scanners and satellite imagery ► Summary  Pixels and scanners  MSS, TM, SPOT, etc  Resolution  Bands  ‘false color’  Comparisons  Image enhancement