Aerial photography and Remote Sensing. Bikini Atoll, 2013 (60 years after nuclear bomb testing)

Transcription

1 Aerial photography and Remote Sensing Bikini Atoll, 2013 (60 years after nuclear bomb testing)

2 Computers have linked mapping techniques under the umbrella term : Geomatics includes all the following spatial technologies: a. Cartography "The art, science and technology of making maps" b. Geographic Information Systems (GIS) "Automated systems for the management, analysis, input and output of spatial data" c. Global Positioning Systems (GPS) "determination of ground locations using measurements from satellites" d. Surveying "science of determination of accurate coordinates of terrestrial locations" e. Photogrammetry "derivation of 2D or 3D locations from stereo pairs of aerial photography f. Remote Sensing "Acquisition of information about a planetary surface from a distance"

3 EARLY REMOTE SENSING Birds, Kites, Balloons, Planes with camera

4 Air photo, World War 1 Reconnaissance and analysis Postwar use limited by resources and the depression Standard for mapping after World War 2

5 Aerial Photography - Flightlines - Overlap - Corrected and mosaicked Panchromatic, Colour, Infra-red

6 BC aerial photography 2007

7 Panchromatic air photo: 15 th / University Way

8 Colour air photo: 15 th / University Way; cost = 2x

9 Microns Panchromatic

10 Remote sensing and the electromagnetic spectrum

11 micrometres: 'microns' : millionths of a metre nanometers: billionths of a metre Blue μm (microns) = 400 to 500 nm nanometres Green μm = 500 to 600 nm Red μm = 600 to 700 nm

12 Birds can see into the Ultraviolet

13

14 1960s: a. wider use of the electromagnetic spectrum b. development of satellites (space race) What is Remote Sensing? "Obtaining information from a distance" = The acquisition and processing of aerial and satellite imagery.. The term first appeared ~1965 with the first satellite images (previously there were only aerial photographs) - Evelyn Pruitt

15 Film has three layers (RGB), a yellow filter removes blue wavelengths, the film is sensitive to infrared, reflected by healthy vegetation, in the red film layer.

16 1950s: Infra-red (IR) photography IR was developed during the Korean War to distinguish between healthy vegetation (reflected IR) and camouflage. Hence it was known as 'camouflage detection' film or 'false colour.

17 PGmap spring 2014 natural colour Advantages of using Infra-Red wavelengths for mapping/gis:

18 PGmap spring 2014 IR image: Land-water distinctions are enhanced (but not urban features) Vegetation differences are enhanced, coniferous v deciduous etc..

19 Most solar energy is in the visible and NIR - These can be captured by cameras - It falls off into the infrared and beyond

20 Scanning (all wavelengths) Beyond nanometres ( microns), the EM spectrum requires 'scanning' A scanner creates digital images (producing images NOT photographs) with layers of pixels (picture elements) - often 8 bit values (0=dark to 255=bright) Close-up of pixels in a digital (scanned) hurricane image <- Prince George scanned IMAGE

21 The near IR ( microns) records energy related to vegetation vigour (health), while the mid- IR ( microns) is (soil) moisture. Neither have anything to do with temperature (or not much) Near-IR Mid-IR

22 Daytime Day and night Thermal Infrared (3-14 microns) This records longer wavelengths and temperature as energy is emitted NOT reflected IR

23 Visible and thermal examples

24 Dusseldorf airport thermal image note the ghost plane shadows Brightness temperature related to surface thermal qualities; brighter = warmer

25 Microwave: (passive) 1mm 1 metre These wavelengths beyond the infra-red can see through' clouds, light rain, and snow, but there is a low amount of it this is why we use these wavelengths for communications.

26 Microwave: - RAdio Detection And Ranging (RADAR) is 'active' remote sensing at wavelengths of 1-30 cm (whereas most other remote sensing is 'passive': recording solar and terrestrial radiation). Passive Active

27 Radar systems were first implemented in the 1930s to detect ships on water and to measure their proximity, and later airplanes. Imaging radar systems have been in use since the 1950s. The original technology was developed during WWII: early german radar. Non-imaging radar

28 RADAR.. was first developed before/during World War II for aircraft detection early imaging RADAR for mapping was airborne. e.g. Intera technologies: 1970s Panama - usually cloudy

29 Longer wavelengths = more clarity, less haze Haze on colour photos is due to shorter blue wavelengths

30 LiDAR = Light Detection And Ranging (visible/nir).. is the other common form of active remote sensing More common since 2000 It is often used to create high resolution DEMs (< 1 metre) Near-IR wavelengths

31 LiDAR 2009 Cranbrook Hill ~ 50 cm resolution

32 2000s Digital photogrammetry Mapping from drones - UAVs Unmanned Aerial Vehicles easily and quickly launched e.g. Colorado 2013 floods Matterhorn: