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