Terrain Analysis

Color Shaded Relief Models

Color shaded reliefs utilize chromo stereoscopic techniques to help emphasize the depth of the Z dimension from traditional DEMs

A color shaded relief (CSR) utilizes chromo stereoscopic techniques to help emphasize the depth of the Z dimension from traditional shaded relief models that already portray the presence of an elevation difference. Using carefully edited RGB (red, green, blue) pseudo colors and then encoding them into the shaded relief image provides the user with an even more enhanced feeling that they can perceive a third dimension from a two-dimensional medium. When a feature of the same color in the image is shaded darker than the shade of its background, then the background color will predominate in determining its perceived depth position in the image.

Digital Elevation Models (DEMS)

Digital elevation model (DEM) of Lismore, Nova Scotia

A digital elevation model (DEM) or sometimes referred to as a digital terrain model (DTM) is a quantitative representation of the topography of the Earth. DEMs are used as a source of elevation (and to create other digital terrain models) for many different purposes

Digital Terrain Modeling

CSR-LIDAR-overpass

Digital Terrain Modeling is the process of simulating or representing the relief and patterns of a surface with numerical and digital methods. It has always been an integral component to geology related fields such as geomorphology, hydrology, tectonics and oceanography but over the past decade has also become a major component to non geophysical applications such as GIS modeling, surveying and land use planning.

Terrain Models are derived from data represented by digital elevation models (DEMs) and can include shaded relief models, slope and aspect models, perspective scene generation, and drainage basin analysis (and other models).

Digital Terrain Modeling – Aspect models

Real world example of slope and aspect

In digital terrain modeling the Aspect of a surface refers to the azimuth to which a slope is orientated. The aspect or orientation of a slope can produce very significant influences on it, so it is important to know the aspect of the plane as well as the slope.Together the slope combined with the aspect of the surface can virtually define the surface plane completely in digital terrain modeling

Example of an Aspect Map

This image is an Aspect Model that I derived from a digital elevation model (DEM) of Lismore, Nova Scotia. The aspect values of the slopes of the DEM are represented in the model by a 0-255 grey scale color ramp. Click here to learn a little more about Aspect Models and how the image below was created.

Slope

image of a cliff demonstrating Slope calculations

The slope or the gradient of a straight line within a Cartesian coordinate system is known as the measure of how steep a line is relative to the horizontal axis. In terrain modeling we generally model an entire surface and not just one line so we need to calculate the slope of a best fit surface plane (which is made of lines). Together the slope combined with the aspect of the surface can virtually define the surface plane completely.