Agriculture Reference
In-Depth Information
Chapter 3
Sensing by Electromagnetic Radiation
Hermann J. Heege
Abstract
Electromagnetic radiation lends itself to non-contact sensing of many
soil- and crop properties. The basis for this is that theoretically any matter - including
constituents of soils and crops - can be identifi ed by an electromagnetic index that
is derived from its radiation. This electromagnetic index can act as an optical fi nger-
print of the respective matter or constituent.
Sensing from satellites or from aerial platforms allows obtaining maps that provide
an overview within approximately the same time about soil- or crop properties from
fi elds or from wider areas for tactical inspections. Sensors that are located on farm
machines never can do this, let alone because of the time it takes to cover a wide area.
Yet when it comes to the control of site-specifi c fi eld operations, sensors on farm
machines can provide the best spatial- and temporal precision that is possible. Their
excellent spatial precision results from the low distance to soils or crops. The high
temporal precision is possible since the signals are recorded just in time. This is
important for those soil- and crop properties that vary fast in time.
Georeferencing by positioning systems allows storing site-specifi c signals.
Keywords
Absorbance Atmopheric windows Clouds Emitted radiation
Georeferencing Optical fi ngerprint Radar Refl ectance Transmittance
3.1
Basics in Sensing by Electromagnetic Radiation
Site-specifi c operations require many samples, therefore, wherever possible, manual
sampling should be replaced by autonomous- or semiautonomous sensing. This
sensing can be accomplished with- or without direct contact to the respective soils
