Not so long ago, a hill top view was the largest vista from which to observe nature's workings. Discoveries in optics, photography and flight have allowed us to see the Earth as never before. Advanced methods in computing and signal processing technologies et cetera have enabled us to increase our ability to visualize and perceive the Earth's surface. Today, Earth observation satellites orbit our planet collecting data needed to produce images which allow us to monitor, understand and plan the use of our world's resources.

animation dimensional shape of land

Throughout history, humans have tried to represent what they saw and understood through images. Everything from cave walls, to canvases, to computer screens have been used to express perception of our surroundings. Maps have been one way to show the relationship between humans and their environment. Towns, roads, rivers, mountains, valleys, and where the land meets the sea, have been drawn in an organized fashion for centuries. Mapmakers have always sought ways in which to represent both the location and the three dimensional shape of land.

The Third Dimension

Mapmakers and other illustrators have traditionally used rendering techniques such as shading, overlapping and perspective views to give an impression of three dimensionality. In the last 200 years, many advances in representing three dimensions have been made. Stereo models, anaglyphs, chromo-stereoscopic images and holograms can provide three-dimensional (3-D) information about our planet that flat, two-dimensional (2-D) images can not. Why is it important that the third dimension be conveyed? Humans are naturally able to see in three dimensions. The 'naturalness' of a 3-D representation of reality enhances our ability to interpret 2-D imagery. Cartographers, engineers, geologists, hydrologists, and other scientists use 3-D viewing methods, such as stereo viewing of aerial photos and satellite images, in order to better understand the Earth's surface. Representation of the third dimension supplies important information about relationships between land shape and structure, slopes, water ways, surface material and vegetative growth.

Stereo viewing of two 2-D images has been used since the mid 1800's. Stereoscopes are still widely used throughout the world. They are much less expensive and much more portable than computer hardware and software. Even though automatic methods to extract quantitative information from a stereo pair have been developed, qualitative interpretation is best handled by people skilled in stereo viewing. For many users and applications, a stereoscope and a stereopair represent the most efficient way of getting a large amount of information about an area of the Earth quickly and inexpensively.

About this training package

The following sections compose a training package designed to demonstrate the feasibility and potential of stereoscopy with respect to RADARSAT data. RADARSAT, Canada's first Earth observation satellite, was launched in November 1995. It is a C-band SAR satellite with the ability to provide imagery of any part of the Earth's surface, in any climatic conditions, and by day or night. RADARSAT imagery is well suited to be used in stereo because it can be collected from different look directions, beam modes, beam positions, and at resolutions fine enough to provide a good level of detail of the Earth's surface. This training package has been divided into six sections which are intended to provide the background needed to fulfil the goal of this manual which is How to Use RADARSAT Data in Stereo. The manual is not intended to review and discuss in great detail the topics in each section. A bibliography has been provided for those interested in pursuing any of the topics in greater detail.