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One of the problems associated with radar is the amount of unwanted clutter (1) on the radar scope which the scanner picks up. This unwanted clutter is mainly echoes of stationary objects, such as mountains and other elevated terrain, as well as other objects situated close to the transmitting/receiving antennae.

With too much clutter, a controller cannot always see the aircraft. MTI (2) allows him to reduce such clutter. The MTI does this by not allowing echoes received from stationary objects to be displayed on the radar scope. A controller has an MTI switch at his console and with this he can control, to a degree, the amount of clutter caused by stationary objects.

However, clutter is not caused by stationary objects only, echoes received from precipitation and/or clouds also cause clutter. MTI is effective in removing clutter caused by precipitation and clouds to a limited extent since MTI permits any echo which is moving to be displayed. So an additional technique known as Circular Polarization (3) has been developed which prevents the display of most of the clutter caused by precipitation and clouds.

While using Circular Polarization, however, controllers would not be aware of the existence of any weather lying ahead of the aircraft, since all echoes from precipitation and clouds would be removed from his scope. Because of this, he could conceivably vector a pilot into turbulent or hazardous (4) meteorological conditions.

A solution to this problem has been to show on the scope the actual weather in the area. This clutter can be switched on and off. Another solution is to feed the weather information into the automaticdataprocessing (5) equipment for incorporation into the controller's computer processed radar scope. This information appears in digital form on the radar scope.

In most radar equipment, the controller is provided with the capability of using MTI alone, MTI plus Circular Polarization, or Circular Polarization alone, thus allowing him a considerable amount of flexibility. (6)

Besides the problems caused by clutter, the slashes (7) on the SSR scope, if too large, could overlap (8) with other slashes making it difficult to distinguish individual aircraft. To keep large slashes apart would require the controller to provide extensive separation between aircraft with resulting delays. This too is improved somewhat with the help of radar automation.

Although most of the deficiencies (9) in radar are characteristic of radar technology, improvements are constantly being made which will assist the air traffic controllers in the future.





1. Clutter ─ The unwanted "snow" or interference on a radar scope caused by fixed or moving objects.
2. Moving Target ─ With MTI a controller can switch off clutter caused by fixed objects such as mountains, buildings, etc.
3. Circular ─ With Circular Polarization a controller can switch off clutter caused by very slow moving objects, such as clouds and precipitation.
4. Hazardous ─ Dangerous.
5. Automatic data processing ─ Another word for computer.
6. Flexibility ─ The ability to change easily.
7. Slashes ─ A return or echo from secondary surveillance radar (not primary radar which is a blip).
8. Overlap ─ One item placed over another item, either partly or completely.
9. Deficiencies ─ Incomplete, lacking perfection.




1. Does a controller see clutter on his radar scope? Do mountains cause clutter on a radar scope? Buildings? Clouds? An aircraft? What is clutter? Can clutter move? Is it easy to see the target with clutter? What type of radar has clutter?

2. Can a controller switch off clutter? With MTI can he switch off stationary clutter? Fixed clutter? With what does he switch off stationary clutter?

3. Can a controller switch off clutter caused by moving objects with CircularPolarization? Stationary objects? What can he switch off with Circular Polarization? Can he switch off the moving target with Circular Polarization? What does he switch off with Circular Polarization?

4. Are hazardous conditions dangerous? Are low clouds around an airport hazardous? Obstructions on the runway? Passengers smoking at take-off? A meal from the galley? What do you consider hazardous in aviation?

5. Is automaticdataprocessing a modern invention? Do we use automatic data processing in aviation? In other fields? Did Marconi (the inventor) have automatic data processing? Who uses automatic data processing?

6. Does a controller have flexibility with Circular Polarization and MTI? Does this flexibility permit him to use Circular Polarization and MTI? Circular Polarization or MTI? Does this flexibility permit him to use Circular Polarization alone? Does this flexibility permit him to show only clouds? Only precipitation? Or both?

7. Are slashes another term for target? Are slashes another term for blip? Echo? Are slashes a description of a dot or a line? Are slashes seen on SSR? Primary radar? On what type of radar are slashes seen?

8. Do two aircraft on the scope appear as one slash when they overlap? Do slashes always overlap on the scope? Sometimes? Partly? Completely? Is it good that slashes overlap on the scope? Why is it necessary to separate them when they overlap?

9. Does everybody have some deficiencies in their character? Is good humour a deficiency? Good manners? What are one's deficiencies? Are there deficiencies in aviation? Can automation help to eliminate some of the deficiencies in aviation? Data processing? Computers? New inventions? Tell me some of the deficiencies inherent in radar.



Instructions to students: Describe in your own words, "The causes and effect of clutter and how a controller handles it".



Date: 2015-12-11; view: 830

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