DE3011556A1 - AREA NAVIGATION SYSTEM FOR AIR AND / OR WATER VEHICLES - Google Patents

Description

7923-35 Bremen, March 24th, 1989

Sm / ka

United Flugtechnische Werke-Fokker limited liability company

Area navigation system for aircraft and / or water vehicles

The invention relates to an area navigation system for Aircraft and / or watercraft with a memory whose data represent previously known height values of an operating area, which are used to determine the position in a correlator with height data processed, which are currently detected in use with a height measuring device.

Navigation systems have been used in aircraft for some time used on the basis of the terrain correlation in order to increase the accuracy of the position determination. A precise position determination is very important, especially in aircraft for military missions, because the success of the respective mission depends on it. Of those that have become known so far Navigation systems promise to work with terrain correlation

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provide the highest accuracy, whereby the existing station independence fulfills an additional requirement for on-board autonomy.

The known navigation systems work with terrain correlation according to the principle of altitude correlation, i.e. the respective altitude to the ground is measured at discrete points and the values recorded in this way are then processed in a correlator with a stored reference altitude of the flight path. the Accuracy of this kind also suitable for watercraft Navigation systems can be significantly increased by "update methods" (refreshing methods). During the travel A special sensor unit is used to trace the elevation profile below via a so-called control area the travel route is measured and the true position is determined by numerical comparison of the quantized terrain data with the stored terrain information serving as reference data.

The previously known navigation systems require for a pre-planned mission a set target course. Although this target course does not have to represent a straight path, it is this is nevertheless unsatisfactory because any, non-prescribed travel routes for military operations are fundamentally are more appropriate.

The invention is therefore based on the object of providing a navigation system of the type mentioned at the beginning * for any use to train non-prescribed travel routes. According to the invention, this object is achieved in that the over a Interface and a data network system coupled «Correlator receives further data from a course and / or position reference system, which is sent to the correlator via a processing stage as well as the data network system and the interface.

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This measure makes it possible, with appropriate design of the Correlator, in particular with appropriate storage of sufficient terrain data, not to follow any prescribed travel routes. The processing level can be derived from the data of the course and / or position reference system, initiated by the height data recorded at the same time, a path template for the future Determine the travel route in the operating area and the altitude data of the operating area stored in the memory for correlation with the recorded height data in accordance with the data determined in each case prepare and rearrange the track template. Furthermore, the processing stage can convert the operating area into virtual ones divide existing control areas into individual correlation areas, with the lengths and / or widths of the correlation areas as a function of the optimal correlation length of the correlation result and the characteristic variable determined by the respective type of terrain for the statistical correlation method as Freely selectable parameters of the processing level can be entered can. The correlation areas within a virtual control area can connect seamlessly, overlap and have a finite distance from one another. It is also useful to have the first correlation area within of a control area to extend over the entire width and the subsequent correlation areas depending on the position determined in the first correlation area to be connected with a reduced width. This procedure also offers the possibility of, when the limits of the Control area by a correlation Geblet in the correlator to trigger a command for course correction. The extent of each Course correction can then be checked in the correlation area that follows the correlation area that triggered the command.

The processing stage can be carried out simultaneously with the altitude measurement and the processing of the altitude values initiated thereby mean course angle from the upcoming course data as entry

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Calculate the angle for the respective control area and use this data the correlator for transforming the control area for the subsequent fine correlation of the into several correlation areas to the divided control area. In the case of the navigation system according to the invention, the altitude data stored in the memory can also be unsorted depending on the data of the respective path template in paths following straight raster lines in order to carry out a line correlation.

The invention is explained in more detail with reference to the accompanying drawing. Show it"

Figure 1 is a block diagram of a navigation system

for any travel route,

Figure 2 shows the principle of operation for a fine

correlation methods,

Figure 3 shows the functional principle for rearranging the Elevation data for a line correlation and Figure 4 shows the functional principle for determining the Entry angle into a control area.

As the block diagram according to FIG. 1 shows, the navigation system according to the invention consists of a TERCOIf unit 1 (TERCOM Terrain contour matching), an altitude measuring device 2, e.g. a radar altimeter and / or a barometric altimeter as well as a course and position reference system 3 The TERCOΜΕ unit 1 consists of a correlator 4, a microprocessor 5, a mass memory 6 and two main memories 7 »3. All of these Construction stages are connected to one another within the TERCOM unit 1 via a data bus 9. Instead of the correlator 4 can several suitably tailored microprocessors

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are set. The data bus 9 continues via an outside the TERCOM unit 1 provided interface 10 to a data network system 11, both with a processing stage 12, the height measuring device 2 as well as with a processing stage 13 of the course and position reference system 3 is in connection. In addition, this data network system 11 can, as indicated, be used for the transmission of data to construction stages not shown in detail, e.g. display devices in the respective carrier vehicle will.

The navigation system according to the invention can be based on a modularη correlation concept, as in our patent application P 28 30 992 described, built and operated. This concept guarantees extensive freedom of movement for any travel routes within an operating area different courses, different types of tracks, different entry angles and different entry points. To take into account the influences of different It is necessary for courses and different forms of orbit that the course and position reference system has sufficient course time accuracy, which is what the devices available today do guarantee.

When operating the navigation system, the preparation of the course information is initiated at the same time as the altitude measurement. During the measurement of the height values in the height measuring device 2 and the subsequent processing in the processing stage the path template is calculated from the course signal and / or the position signal of the course / position reference system. Before the actual correlation calculation is carried out, the stored altitude setpoints are stored in the memories 6, 7, 8 accordingly the data of the web template prepared and re-sorted. In this way it is ensured that the influences of any orbit shapes on the correlation result and thus the accuracy of the Navigation statements are taken into account. The signals of the web template processed in the processing stage 13 are transmitted via the

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Interface - data network system 11 - in the TERCOM unit transfer*

In operation of the area navigation system according to the invention three different functional principles possible depending on the route. What these principles have in common is the method of calculating the Position updates (renewal) and, darttberhlnaus, the determination of course and speed information. As shown in Fig. emerges, a so-called virtual control area 15 is defined, which is made up of individual correlation areas 16, 17 ··· 22 consists. The individual correlation areas 16, 17 ·· ♦ · 22 can either overlap - as shown -, a finite one Have a distance from one another or connect seamlessly. The length of the correlation areas becomes the optimal one Correlation length selected, the one characteristic for the respective type of terrain and the statistical correlation method Represents size. While the width of the first correlation area 16 in the control area 15 is the width of the control area corresponds to the following correlation areas 17, 18 .... 22 with reduced width The security of the navigation information is significantly increased because this eliminates outliers »Before the final update information is calculated, the number of Correlation areas determined several position information. With a simple decision logic (quality of the correlation criterion or smoothing) the first current position in the Correlator 4 determined. If the length of the control area is significant, it can be calculated repeatedly the travel route within the control area and additional course errors can be determined.

The principle of fine correlation shown in FIG. 2 with the The associated trajectory determination also facilitates the search process. Starting from the correlation area 16 in which because of the maximum entry error, the search strategy is based on the

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must cover the entire width of the control area can be in the following correlation areas 17. ·. 22 the correlation process to a range predicted around the last position be restricted. A correlation window appears to be more constant but reduced over the entire length of the control area Width moved according to the travel route, the criterion being the course of the correlation function. The feed takes place with a the clock equivalent to the integer multiple of the grid spacing. The synchronization between setpoint and actual values is done via the speed information of the course and position reference system ensured, so that in this way from the continuously recorded altitude measurement sequence for the correlation over the respective Correlation window (area) valid actual value strips can be selected. The individual correlation calculations are thereby not carried out along the saved grid lines, but with the current path template.

As the embodiment of Figure 3 shows, it is also possible perform the correlation on curved paths along straight lines. Here, the principle of line correlation along stored grid lines after the re-sorting is applied. The essential one The difference compared to the other functional principles is that before the correlation calculation is carried out accordingly of the prepared path template, the target values of the stored terrain height matrix are rearranged. As Figure 3 shows, is included a control area 30 covered with a grid, whereby in this Control area 64 Raeter cells 31 arise «The correlation between the rearranged setpoint values and the measured actual values are carried out along the new grid lines 33t 34 shown next to them, i.e., there is an apparent correlation with the path template 32. With this principle of operation, the curved paths 32 in the straight paths 33t 34 transformed and then carried out a line correlation, the calculation of the current Position takes place according to the procedure described so far.

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With this functional principle, the following can be used in the construction stages of the TERCOM unit 1, depending on the programming Steps are differentiated »

1. Initiation of altitude measurement and course preparation,

2. Determination of the actual terrain height profile,

3. Calculation of the data of the path template *

After performing a correlation

4. Adoption, decompression and storage of the measured height profiles along the travel route,

5 transfer of the web template, 6. Preparation of the setpoints

6.1 index calculation,

6.2 !! ^ storage τοη main memory in memory 8 and

6.3 weighted interpolation

7> Multiple correlation along the new grid lines, 8. Determination of the current position by a decision logic,

9 * back transformation into the geodetic system and 10. Transfer of the current position values.

In addition to the course preparation initiated by the altitude measurement, it is also possible to record the course angle. The figure shows the functional principle for the determination of the mean course angle q £ and the transformation of the correlation area 25 within the control area 24 in a phase that is not time-critical for the entire execution of the correlation. The time criterion required for the correlation time remains unaffected due to the recursive mode of operation. The coarse correlation around the

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mean course angle OC along the transformed parallel the grid line 27 lying to the path template 26 results in a very precise first approximation for the position to be determined. With the subsequent fine correlation, which takes place with the prepared path template 26, an exact determination is made the position in a narrow sector around the position determined in the first approximation. This will make the Signal processing overhead and the time to complete a Correlation significantly reduced.

During a position determination process, the TERCOM unit 1 is determined by a corresponding program in the construction stages, carried out the following steps!

1. Initiation of altitude measurement and course preparation,

2. Determination of the terrain height profile,

3. Determination of a mean course angle (best-fit straight line), 4 * transformation of the correlation area around the mean

Heading angle, Decompression to absolute altitude values, Determination of the coordinates x, y to be transformed Index calculation, Interpolation, Calculation of the related to the mean value

Values,

Dm storage of a control area.

After completion of a correlation process, the following steps are carried out in TERCOM unit 1, also depending on the programming carried out!

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Acquisition, decompression and storage

the measured height profiles along the travel route,

Acceptance of the mean course angle, Coarse correlation of the stored and measured Height profiles in the wired grid of the operating area,

Fine correlation with the path template in the restricted search area,

Determining the position, Back transformation into the geodetic system and

Transfer of the current position values.

The area navigation system according to the invention is due to the Acquisition and appropriate processing of the course and speed information, able to follow any, non-specified travel routes and therefore particularly suitable for military missions. The prerequisite for this is that the elevation data of the operating area are available in the memories 6, 7 and 8, but this is due to today's Storage technology is possible without great effort.

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7923-35 _t A \ L. Bremen, February 26th, 1960

Sra / k

Compilation of the reference numbers

1 TERCOM unit 2 Height measurement in the direction 3 Course and attitude reference system 4th Correlator 5 microprocessor 6th Mass storage 7th random access memory 8th _ Il _ 9 Data bus 10 interface 11 Data network system 12th Processing stage 13th 15th Control area 16 Correlation area ■ · ·
22nd 23 Orbit template 24 Control area 25th Correlation area 26th Orbit template 27 Grid line

30 control area

31 correlation area

32 curved track

33 straight track

34 - »-

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Claims (11)

7923-35 Bremen, February 26th, 1989 Sm / ka Vereinigte Flugtechnische Werke-i Gescl ]schrift and limited liability Claims Area navigation system for aircraft and / or watercraft with a memory whose data is previously known Represent elevation values of an operating area that are used to determine the position in a correlator Altitude data are processed, which are currently recorded in use with an altitude measuring device, thereby characterized in that the via an interface (lO) and a data network system (ll) with the height measuring device (2) coupled correlator (4) receives further data from a course and / or load reference system (3), via a processing stage (l3) and the data network system (ll) and the interface (10) to the correlator (4). 2.) Area navigation system according to claim 1, characterized in that the processing stage (13) from the data of the course and position reference system (3), initiated by the altitude data recorded at the same time, a path template (23, 26, 32) determined for the future travel route in the operating area and that the memory (6, 7> 8) stored elevation data of the operating area for correlation with the acquired elevation data according to the respective determined data of the web template (23, 26, 32) are processed and re-sorted. 1300A0 / 0608 ORIGINAL INSPECTED 3 ·) Area navigation system according to claim 1 or 2, characterized characterized in that the processing stage (13) virtually consists of individual correlation areas (16 ... 22) existing control areas (15, 24, 30) and that the Lengths and / or widths of the correlation areas (16 .... 22) depending on the optimal correlation length and the characteristic variable determined by the respective type of terrain for the static correlation method as free Selectable parameters of the processing level (l3) can be entered are. 4 ·) Area navigation system according to claim 3 »characterized in that the correlation areas (16 ... 22) within a virtual control area (15) overlap one after the other. 5 ·) Area navigation system according to claim 3, characterized in that the correlation areas have a finite distance from one another within a virtual control area. 6.) Area navigation system according to claim 3, characterized in that the correlation areas can be seamlessly lined up within a virtual control area. 7.) Area navigation system according to one of claims 1 to 6, characterized in that the respective first correlation area (l6) is within a control area (15) extends over the entire width and that the following correlation areas (17 ··· 22) are as a function of those found in the first correlation area (16) Connect position with reduced width. —3— 130040/0608 8.) Flächennavigatibnssystem according to one of claims 1 to 7, characterized in that the following the first correlation area (l6) in a control area (l5) Correlation areas (17-22) of reduced width when reaching the border of the control area (15) im Correlator (4) trigger a command to correct course. 9) surface navigation system according to one of claims 1 to 0, characterized in that the extent of the course correction triggered in the correlation areas (19 ··· 22) is checked, which is the one that triggered the command Correlation area (lÖ) follow. 10.) Area navigation system according to one of claims 1 to 9 »characterized» that the processing stage (13) simultaneously with the altitude measurement and the processing of the altitude data initiated thereby the mean course angle (Q ^) from the upcoming course data as the entry angle into a respective control area ( 24) is calculated and this data is fed to the correlator (4) to transform the correlation area (24) for the subsequent fine correlation. 11.) Area navigation system according to one of the preceding claims, characterized in that the Altitude data stored in memory (6, 7 »8) as a function of the data of the respective path template (32) in a straight grid lines following path (33 »34) for implementation a line correlation are rearranged. 130040/0608