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Aerial photography and satellite imagery as data input

Aerial photography and satellite imagery as data input. GEOG 4103, Feb 20th Adina Racoviteanu. Aerial photographs. "bird's-eye" view of the earth Photogrammetry = "the art or science of making measurements from aerial imagery". K-25 WWII Recon Camera. Camera systems.

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Aerial photography and satellite imagery as data input

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  1. Aerial photography and satellite imagery as data input GEOG 4103, Feb 20th Adina Racoviteanu

  2. Aerial photographs • "bird's-eye" view of the earth • Photogrammetry = "the art or science of making measurements from aerial imagery"

  3. K-25 WWII Recon Camera Camera systems High Quality Photographic Systems and the Digital Modular Camera

  4. angle Nadir Uncorrected Aerial photographs • Uncorrected aerial photos have distortions • radial distortion (due to lens curvature) • geometric distortions (due to inconsistencies in the • attitude of the airplane) • topographic distortions (due to relief)

  5. Uses of aerial photgraphy • Corrected images are often called orthoimages • GIS applications: land use and land-cover classification, terrain analysis, natural resource mapping, image backdrops for maps, temporal-change analysis, etc...

  6. Black and white aerial photography

  7. Color aerial photography

  8. Stereoscopy (three-dimensional imaging) any technique capable of recording three-dimensional visual information or creating the illusion of depth in an image;

  9. FUNDAMENTALS OF REMOTE SENSING • Energy source • Atmospheric interactions • Target interactions • Sensor records energy • Transmission to receiving station • Interpretation • Application

  10. Gamma Rays X rays Ultra-violet(UV) Visible (400 - 700nm) Near Infrared (NIR) Infrared (IR) Microwaves Weather radar Television, FM radio Short wave radio The EM Spectrum 10-1nm 1 nm 10-2mm 10-1mm 1 mm 10 mm 100 mm 1 mm 1 cm 10 cm 1 m 102m Violet Blue Green Yellow Orange Red

  11. PIXELS: Minimum sampling area One temperature brightness (Tb) value recorded per pixel

  12. Landsat Thematic Mapper (TM) • 30 m spatial resolution • 185 km FOV • Spectral resolution • 0.45-0.52 μm • 0.52-0.60 μm • 0.63-0.69 μm • 0.76-0.90 μm • 1.55-1.75 μm • 10.4-12.5 μm • 2.08-2.35 μm • 16 day repeat pass

  13. EOS Terra MODIS • Image Earth’s surface every 1 to 2 days • 36 spectral bands covering VIS, NIR, thermal • 1 km spatial resolution (29 bands) • 500 m spatial resolution (5 bands) • 250 m spatial resolution (2 bands) • 2330 km swath

  14. Digital processing2 steps needed: 1) Georeferencing: assign real world coordinates 2) Orthorectification: remove all the distortions

  15. Georeferencing • Assigning real world coordinates • Relating information (e.g., documents, datasets, maps, images) to geographic locations • will correct displacements Discrete georeferencing: through place names (i.e., toponyms) and place codes (e.g., postal codes) Geospatial referencing (e.g., longitude and latitude coordinates).

  16. Discrete georeferencingor Geocoding • The process of assigning a geographic location (e.g. latitude and longitude) to a geographic feature on the basis of its address. • E.g. address matching • mapquest.com

  17. Geocoding method • Based on a parcel centroid file that includes: • Street Name • Address • Nine-Digit ZIP Code • Main source for geocoding base map data is TIGER (http://www.census.gov/geog/www/tiger/)

  18. Ground Control Points (GCPs) • To georeference an image we need GCPs which are visible in the photographs, • e.g road intersections, stone wall boundaries, building corners, and solitary trees. • These points will be used to “tell” the GIS software: • where your image is in the world • how to correctly orient the photograph • correct for errors in photo-geometry.

  19. Road curves Rivers Squares Ground Control Points (GCPs) collection X • 24 GCPs – differentially • corrected GPS (vertical and • horizontal accuracy < 1m) • Orthorectification

  20. How many GCPs? • Depends on the amount of distortion in your photograph and your desired level of accuracy • mathematical formula applied to each pixel in the photo • first order (3 points min) does not distort, only shifts • second order (6 points min) • third order (9 points min) - distortions

  21. Georeferencing to an image file in ArcMap: Spatial data (polygons, points, etc.) can be aligned to an image file such as an historical map, satellite image, or aerial photograph.

  22. GCP Georeferencing terrestrial photography

  23. Orthorectification • mathematical process of removing the distortion caused by relief and the camera within a photograph so that the scale is uniform throughout the output image.

  24. Distortion vs.displacement • Distortion - Shift in the location of an object that changes the perspective characteristics of the photo. • Displacement - shift in the location of an object in a photo caused by change in elevation.)

  25. Orthorectification A sports stadium in downtown Toronto before and after rigorous orthorectificationImagery courtesy of DigitalGlobe

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