Guess the Geometry of

a) b)

1. the Navigation Accuracy Measurement System (NAMS)

2. configuration of the height measurement system with a single air-traffic control radar.

8.Look at the pictures and discuss in pairs (groups):

- main principles of devices (antenna, radar)

- describe the geometry (a; b)

Translate into Ukrainian.

1. The pilot must keep flying on an isobaric surface.

2. Interest focuses on the measurement of the distance between aircraft level and the sea surface level.

Retell text A.

10.Circle the correct form in parentheses.

1. Rita plays the violin (good/well).

2. That is an (intense/intensely) novel.

3. The sun is shining (bright/brightly).

4. The girls speak (fluent/fluently) French.

5. The boys speak Spanish (fluent/fluently).

6. The table has a (smooth/smoothy) surface.

7. We must figure our income tax returns (accurate/accurately).

8. We don't like to drink (bitter/bitterly) tea.

9. The plane will arrive (soon/soonly).

10. He had an accident because he was driving too (fast/fastly).

11.What do you know about altitude? Find appropriate answer.

Read and translate text B.

TEXT B

The research and development of the GPS has been coordinated by the U.S. Department of Defense. Another similar system is the Global Navigation Satellite System – GLONASS (Fig.16.2). The GPS is a satellite system providing users with accurate timing and ranging information. The system is available with reduced accuracy to civilian users. Many companies, mainly from the U.S., produce GPS receivers.

Figure 16.2. GLONASS

In some systems, there are singular cases for which it is not possible to achieve a position fix. This fact has been reported by Abel and Chafee for the GPS system, where it is not possible to solve the relevant equation or there is more than one solution. Also it has been shown by Manolakis and Lefas that there are some station arrangements for which it is not possible to derive height estimation when the aircraft is at specific areas. For example, in the case of four stations, when the quadrilateral defined by the stations is inscribed in a circle, it is not possible to estimate the height when the aircraft is above the center. Also, when the quadrilateral is a rectangle or symmetric trapezoid, it is not possible to derive a position fix when the aircraft is above the line that passes from the middle of the parallel sides. From a mathematical point of view, this singularity is expressed by the singularity of the Jacobian matrix; consequently, this matrix cannot be inverted as is required by the relevant position estimation algorithm. The algorithm in this case diverges from the actual height and finally collapses. Notice that height estimation is achieved everywhere except at this singular point (Fig.16.3). However, when the aircraft is close to the singular region, although a position fix is achieved, it is not actually reliable since it is affected by large errors; for example, the VDOP could be larger than 600 in regions close to the singular region.

Figure 16.3. GPS signal modulation scheme

To anticipate for the error intentionally induced by the Department of Defense, the Differential GPS (DGPS) method has been developed. A station located at a precisely known position receives the satellite signals, computes its own position on the basis of pseudorange measurements, compares this position with the known position in order to estimate the included error in satellite signals, and finally transmits the appropriate corrections to the receivers in its neighborhood. The achieved accuracy is in the order of a few meters.

Date: 2016-04-22; view: 876