The key concept of radar is relatively simple but its practical implementation could be very
complicated. An active radar radiates electromagnetic energy and detects the echo
returned from reflecting objects (targets). The nature of the echo signal provides
information about the target. The distance to the target determines the time of the radiated
energy to travel to the target and back. The angular location defines a directive antenna. A
radar can derive the target trajectory, and predict future location. With sufficiently high
resolution, the radar can distinguish something about a target's size and shape. Usually,
the radar is an active device in that it carries its own transmitter and does not depend on
ambient radiation, as do most optical and infrared sensors. The radar can detect relatively
small targets at near or far distances and can measure their range with precision in all
weather. On the other side, the passive surveillance technology provides an unmatched
ability to "see without being seen" and provides the very advanced technology. The
described properties are very useful for transportation. The students of University of
Pardubice and their teachers have cooperated on the development of various kinds of
radars produced in the Czech Republic. Several examples such as air traffic control, river
and automotive radars, which are used in transportation, are briefly illustrated.