Operations in the urban environment are concentrated on the individual soldier and on small groups. It is an up-close and personal environment. Nonetheless, the fundamental problems facing those involved are military constants: Where am I? Where are my friends? How do I co-ordinate with them? Where is the enemy?
The nature of the terrain dictates that the most useful equipment to help answer these questions is that which can be carried easily and directly supports the battle at the applicable level.
Where am I?
The Global Positioning System will provide all the positional information that the soldier and the low-level commander need, but it is dependent on satellite communications. There are times when GPS communications do not work, notably inside buildings. An alternative is therefore needed that will take over the provision of positional data to the soldier until GPS connectivity is restored.
One such system is the patented Dead Reckoning Module from Point Research in California. The Dead Reckoning Module is a miniature, self-contained, electronic navigation unit that provides the user's position relative to an initialisation point (usually provided by GPS). It contains a tilt-compensated magnetic compass, electronic pedometer and barometric altimeter to provide a continuous deduced position. A microprocessor performs dead reckoning calculations and includes a Kalman filter to combine the dead reckoning data with GPS data when it is available. The filter and other proprietary algorithms use GPS data to calibrate dead reckoning sensors for a typical dead reckoning accuracy of two to five per cent of distance travelled, entirely without GPS.
A similar offering is the Pedestrian Navigation Module from Swiss optical device firm Vectronix. It is basically a pedometer that detects steps and changes in acceleration, linked to a digital compass, a barometer (to detect changes in height) and a gyro. The software developed by Vectronix fuses the data received from these sources, providing positional information which can then be displayed on a digital map, either on a hand-held display or injected into a helmet-mounted system. The advantage of this system is that it is independent of GPS, so is ideal for use in urban and other areas where GPS may not always be available.
There is other navigational equipment which is associated with particular communications systems, of which more below.
Buildings affect VHF and UHF radio communications, normally used at the tactical level, in different ways. The radio waves have trouble penetrating reinforced concrete exterior walls and are likely to be reflected from these. They can pass through windows and light interior wall partitions relatively easily, although with some loss of power. When a VHF or UHF wave comes to a sharp edge, such as the edge of an opening or the corner of a building, a portion of the wave bends round it and continues propagation.
Terrestrial radio communications in the urban environment--i.e., between one radio and another on the ground--can be blocked altogether, and will certainly be degraded, difficult and intermittent, particularly from outside to inside a building. Satellite communications will also be affected, either because access to a satellite is blocked by overhead obstruction (when inside a building) or by the 'canyon' effect of streets. The latter may, of course, be overcome by moving into the open in the middle of the street, but this is unlikely to be advisable or desirable.
Troops within a few yards of each other can be out of visual contact. Shouting then becomes the only means of communication, but to do so is anything but covert and inside buildings noise is magnified and confused. The advent of individual radios for soldiers has made a significant contribution to urban tactical control.
One of the most widespread examples of this is the Selenia Communications H4855 Personal Role Radio (PRR), which is a short-range simplex radio system operating in the 2.400 to 2.483 GHz...