A digital elevation model (DEM) is a digital representation of ground
surface topography or terrain. It is also widely known as a digital
terrain model (DTM). A DEM can be represented as a raster (a grid of
squares) or as a vector based triangular irregular network (TIN). DEMs
are commonly built using remote sensing techniques, but they may also be
built from land surveying. DEMs are used often in geographic information
systems, and are the most common basis for digitally-produced relief
maps. The terrain surface can be described as compromising of two
different elements; random and systematic. The random (stochastic)
elements are the continuous surfaces with continuously varying relief.
It would take an endless number of points to describe exactly the random
terrain shapes, but these can be described in practice with a network of
point. It is usual to use a network that creates sloping triangles or
regular quadrants.
This book examines how the methods and data sources used to generate
DEMs and calculate land surface parameters have changed over the past 25
years. The primary goal is to describe the state-of-the-art for a
typical digital terrain modeling workflow that starts with data capture,
continues with data preprocessing and DEM generation, and concludes with
the calculation of one or more primary and secondary land surface
parameters. Taken as a whole, this book covers the basic theory behind
the methods, the instrumentation, analysis and interpretation that are
embedded in the modern digital terrain modeling workflow, the strengths
and weaknesses of the various methods that the terrain analyst must
choose among, typical applications of the results emanating from these
terrain modeling workflows, and future directions.
This book is intended for researchers and practitioners who wish to use
DEMs, land surface parameters, land surface objects and landforms in
environmental projects. The book will also be valuable as a reference
text for environmental scientists who are specialists in related fields
and wish to integrate these kinds of digital terrain workflows and
outputs into their own specialized work environments.
