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Image Processing & GIS Integration for Environmental Analysis
Image Processing & GIS Integration for Environmental Analysis
School of Electrical & Electronic Engineering
The Queen’s University of Belfast
Paul Kelly
Objective Environmental Analysis
Objective Environmental Analysis
• Currently two extremes– Satellite image only low-resolution roof /
surface canopy visible– Detailed individual plant samples
• Gap currently filled by manual subjective scene analysis
• Economic & Versatile method of surveying moderately-sized areas needed
Existing ResearchExisting Research
• Agouris (’00) GIS integration with aerial photographs
• Broggi (’98) Perspective transformation, only for flat scenes
• McMenemy [QUB] (’01) DV Camera Calibration and use in photogrammetry
• Multi-disciplinary subject
Data Types & ProcessingData Types & Processing
• Raster: pixel-level (colour)
• Vector: object-level
• Sources– Ground-level Images captured with Digital
Video camera (raster)– GIS Digital Map Data (mainly vector)– Aerial Photographs or Satellite Images
(raster)
Change Detection Preliminaries
Change Detection Preliminaries
• Comparison only possible between images of the same view of same scene
• These parameters must be equal:– Observer (camera) location– Centre of View– Camera Parameters (Field of View, focal length,
CCD Array Dimensions)
• Perspective Transformation transforms an image so they appear equal
Methodology OutlineMethodology Outline
1. Initial Image Correction
2. Camera Location Measurement
3. GIS Data
4. Ground-level Image / GIS Processing
5. Aerial / Satellite Image Integration
6. Change Detection (Preliminary Results)
Initial Image CorrectionInitial Image Correction
• Colour Response Calibration
– Dark Image
– Response Curve calibration with Luxmeter
• Lens Barrel Distortion
– Image of grid of known points
– Best-fit transformation equation
– Bi-linear Interpolation
Original Distorted
Distortion CorrectionDistortion Correction
Original DistortedCorrected
Camera Location Measurement
Camera Location Measurement
• GPS
• Accelerometer
• Electronic Compass
• Sensor Fusion and processing results in
Position (Easting, Northing, Elevation)
and Orientation for GIS input
GIS DataGIS Data
• Supplied by Ordnance Survey (NI):— 1:1250 or 1:2500 scale Vector map data
— 50 metre resolution digital elevation data— 1:50000 scale contour lines— Spot heights (mainly on main roads and benchmarks) included in Vector maps
Feature & Building Outlines etc.
Elevation / 3rd Dimension data, to be interpolated into a Digital Elevation Model
Ground-Level ImagesGround-Level Images
• Commercial Digital Video DV Camera• Experimentally calibrated for
– Field of View– Focal Length– CCD Array Dimensions
• Thus enabling– Photogrammetric Calculations– Generation of ‘Camera-eye Views’ in GIS or
otherwise
GIS 3-D ViewGIS 3-D View
3-D Landscape ViewField Boundaries overlaid on Image
Aerial / Satellite ImagesAerial / Satellite Images
• Require georeferencing in GIS— polynomial approximation may be used
• Images used for– Initial detection of where change has
occurred—pointer to more detailed ground observation and analysis
– Framework for referencing ground-level images to
Aerial / Satellite ImagesAerial / Satellite Images
Russian satellite image from 1988
Blue lines: edge-detected from satellite image
Red lines: GIS Building Outline Data
Change Detection MethodsChange Detection Methods
• Illumination and Daylighting Compensation (Use calibration object)
• Vector / Vector Comparison– ‘Rasterised Vector’ Image created by
segmentation and edge detection– Objects displaced or changed shape?
• Raster / Raster Comparison– Surface features, e.g. colour changed?
Further GIS UseFurther GIS Use
• GIS 3-D View related pixel-by-pixel to original image
• Calculate Easting, Northing & Elevation for each pixel
• Use referenced pixel values to re-create the view from a different perspective
• Works well in areas with few objects above ground
6 January2002
24 April2002
Further GIS UseFurther GIS Use
Aerial Views
With some illumination
compensationDifference
Image
SummarySummary
• Calibrated Camera Images
• GIS Digital Map Data
• Innovative Image Alignment Methods
• Vector & Raster Change Detection
• GIS use significantly enhances Image Processing & Photogrammetry capabilities