JPH03273182A - Radar device - Google Patents

Abstract

PURPOSE:To properly display the moving locus of a body to be detected such as an island by providing a reception part, a buffer memory, a signal processing means which supplies a moving locus signal read out of a 1st memory to 1st and 2nd memories, and a display device. CONSTITUTION:A moving locus signal generation part 4a converts an echo signal outputted from the buffer memory 3 into data for an image display and supplies it to a frame memory 6 and a moving locus signal processing memory 8a. Further, the moving locus signal, etc., is generated according to the output signals of the memories 3 and 8a. This generation part 4a ignores a low signal level like an unnecessary reflected wave from the sea surface, etc., as to the signal outputted from the memory 3 and supplies only a signal of high level like a reflected wave from an island, other ships, etc., to the memory 8a. Whatever display mode is specified, a write address of the memory 8a is always a write address in true motion mode and north-up mode (TEM.NU mode), so a past signal from the memory 8a and a current signal from the memory 3 can be made to accurately correspond to each other.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention receives echo signals returning from each direction by sequentially emitting radar detection signals in different directions while rotating the antenna, writes the echo signals into an image memory, stores them, and then reads them out. The present invention relates to a radar device that supplies information to a display device and displays the surrounding situation of a radar antenna on its display screen, and particularly relates to a device that can accurately display the movement trajectory of an object to be detected, such as an island or another ship. [0002]

[Conventional technology]

A conventional radar device will be explained with reference to FIG. That is, the receiver 1 receives and detects and amplifies one beam of echo signals returning from each direction due to detection pulse signals sequentially emitted in different directions as a radar antenna (not shown) rotates. The received signal of one beam from this receiver 1 is A
The signals are A/D converted by the /D converter 2 and temporarily stored in the buffer memory 3 in chronological order. The received signal (echo data) supplied from the buffer memory 3 is converted by the write data creation section 4 into data for image display. [0003] Output data from the write data generation section 4 is written to the frame memory 6 at a write address generated by the write address generation section 5. The data written in the frame memory 6 is read out based on the read address generated by the read address generation section 7 according to the rask scan method. The read data is displayed as an image on a display device such as a CRT (not shown). [0004] The write address generator 5 generates a write address consisting of orthogonal coordinates (x, y) based on the antenna direction, the course of the own ship, the position of the own ship, the specified display mode, etc. -Perform Cartesian coordinate transformation. This conversion is performed based on the following equation. X=Xc+Rs in
θY=Yc+Rcosθ (However, in the case of HU display, θ=θ, in the case of NU display,
θ = θ months + θ6, in case of CU display, θ = θ□ + θG - θ
It becomes C. ) Xc, Yc are own ship position addresses on the frame memory, R is the distance from the own ship position, θ is the angle in the sweep direction from the Y axis (frame memory), θ. is the antenna angle with respect to the bow direction, θG is the own ship's course, and θG is the set course. [0005] In the above-mentioned radar device, when the readout for display on the display is performed using the rask scan method, the write address generation unit 5 is configured to perform coordinate conversion from polar coordinates to rectangular coordinates. When using the scan method, there is no need to perform the above-mentioned coordinate transformation in the write address generation section 5. [0006] In the conventional radar device described above, the mode setting unit (not shown) selects north up mode (hereinafter abbreviated as NU mode), head up mode (hereinafter abbreviated as HU mode), and course up mode. mode (hereinafter abbreviated as CU mode), three display modes can be selected. [0007] ■ In the NU mode, as shown in FIG. 10, the area directly above the display screen always points north. In this case, images of fixed targets such as fixed buoys are always displayed in the fixed position regardless of the direction of the ship's bow, but if the ship's bow is facing north, the ship's bow line will be at the position indicated by the solid arrow; When you change direction to the east, the bow lines will be displayed at the positions indicated by the dashed arrows. ■ In the HU mode, as shown in FIG. 11, the point directly above the display screen always points to the bow. In this case, the bow line is always displayed pointing directly above the display screen regardless of the bow direction, but if the bow direction is set to north, fixed images such as fixed buoys will be at the A1 position, and the bow direction will be When changing to the east, the fixed image is displayed at the A2 position. [0008] ■ In the CU mode, as shown in FIG. 12, what is directly above the display screen always indicates the preset scheduled course of the ship. In this case, images of fixed targets such as fixed buoys are always displayed in the fixed position regardless of the direction of the ship's bow, but if the ship's bow is facing north, the ship's bow line will be at the position indicated by the imaginary line, and When you change direction to the east, the bow lines will be displayed at the positions indicated by the dashed arrows. [0009] In this way, in the NU mode and the CU mode, a fixed target is displayed at a fixed position on the display screen, and the bow line is displayed at a different position on the display screen depending on the direction, and in the HU mode, The bow line is displayed at a fixed position on the display screen, and fixed targets are displayed at different positions on the display screen depending on the direction of the bow. [00101] By the way, depending on whether the own ship's position is fixed and displayed or moved according to the amount of movement of the own ship, there are relative motion mode (hereinafter abbreviated as RM mode) and true motion mode (hereinafter abbreviated as RM mode). , TM mode), and the operating mode to be used can be specified by the operator via a mode setting section (not shown). [0011] ■ In the RM mode, as shown in Figure 8, the own ship position (beam center) is displayed fixedly at a specific position (the center in the figure) on the display screen, and the position is fixed according to the movement of the own ship. Move and display the target. [0012] ■ In TM mode, as shown in Figure 9, the own ship's position (beam center) is moved and displayed on the display screen according to the own ship's speed and course, and the fixed target is placed at a specific position. Fixed display. [0013] Note that RM mode can be combined with all of NU, HU, and CU modes, and TM mode can be combined with NU mode and CU mode.
Although it is possible to combine the two U modes, combination with the HU mode is not possible. this house,
A relatively frequently used combination is RM-HU mode and T
There are two modes: M-NU mode. In the RM/HU mode, the screen displays as if the operator were on a ship, and in the TM-NU mode, the screen displays as if the ship were moving on a map.

[0014]By the way, due to requests such as wanting to know the approach of other ships, it is desired to display the movement trajectory of objects to be detected, such as islands and other ships. In order to display such a movement trajectory of the detected object, it is possible, for example, to write the current received signal and past received signals in the frame memory 6 in an overlapping manner, and provide the data to the display. . In order to perform such processing in the conventional radar device, the signal from the buffer memory 3 is used as the current signal, the signal from the frame memory 6 is used as the past signal, and the write data creation unit 4 processes the signal. It is conceivable to write the processed signal into the frame memory 6 again. [0015]

[Problem to be solved by the invention]

By the way, the process of displaying the movement trajectory of objects to be detected, such as islands or other ships, is performed by combining the current echo signal given from the buffer memory 3 and the past echo signals already written in the frame memory 6, as described above. Of the frequently used combinations mentioned above, it is possible to execute them in the TM-NU mode, but it is impossible to execute them properly in the RM-HU mode for reasons explained later. It is. [0016] In other words, in the conventional radar device described above, among the display modes on the display, in the TM-NU mode, the amount of movement of the own ship is changed, such as when the own ship is traveling at high speed or when the detection range is small. When displaying a case that cannot be ignored, even if the data written to the frame memory 6 for one rotation of the antenna is updated moment by moment, the data written to the frame memory 6 may change due to changes in the position of own ship or changes in the own ship's position. However, in the RM-HU mode, the data written to the frame memory 6 is affected by changes in the position of the own ship and the turning of the own ship. [0017] The present invention was devised in view of the above circumstances, and its main purpose is to enable the movement trajectory of a detected object to be appropriately displayed regardless of the display mode. [0018] Another object of the present invention is to enable the movement locus of a detected object to be displayed appropriately and to perform correct scan correlation processing regardless of the display mode. [0019]

[Means to solve the problem]

In order to achieve such a problem, the present invention provides a radar device that sequentially emits detection signals in different directions, receives returning echo signals, and displays the surrounding situation in a wide range of directions on a display device. The structure is as follows. [00201] The first radar device of the present invention (corresponding to claim 1) includes a receiving section that receives an echo signal, a buffer memory that temporarily stores an echo signal caused by a detection signal sent from the receiving section, and the following: a first memory that stores the signals given from the signal processing means at address positions corresponding to respective points on the earth's surface where the echo signals are generated; and a buffer memory that stores the signals given by the echo signals from other ships, etc. Signal processing that provides a movement trajectory signal (a signal representing the movement trajectory of an object to be detected, such as an island or another ship) obtained by signal processing the past echo signal read out from the first memory to the first memory and the second memory. and a second memory for respectively storing the movement trajectory signal output from the signal processing means at an address position determined by a set display mode, and a display for displaying the signal read from the second memory. Has characteristics. [0021] A second radar device of the present invention (corresponding to claim 2) includes a receiving section that receives an echo signal, a buffer memory that temporarily stores an echo signal caused by a detection signal sent from the receiving section, a first memory that stores signals given from the signal processing means described below at address positions corresponding to each point on the earth's surface where the echo signals are generated, and a buffer memory that outputs current echo signals from other ships, etc. and a past echo signal read out from the first memory to provide a movement trajectory signal (representing the movement trajectory of an object to be detected such as an island or another ship) to the first memory and second memory. a second memory that stores signals output from the signal processing means and the correlation means described below at address positions determined by the set display mode, respectively; A third memory stores each point at an address corresponding to each point on the surface, and correlates the current echo signal outputted from the buffer memory with the past echo signal read out from the third memory, and processes the correlation to produce an output signal. The present invention is characterized in that it comprises a correlation means for providing a signal to a third memory and a second memory, and a display device for displaying a signal read from the second memory. [0022]

[Effect]

In the first radar device of the present invention, the signal output from the signal processing means is stored in the first memory at an address position corresponding to each point on the earth's surface where the echo signal occurred.
The current echo signal outputted from the buffer memory and the past echo signal outputted from the first memory can be matched without being affected by changes in the amount of movement and course of the own ship. Therefore, if an object to be detected, such as an island or another ship, is moving, the data representing the object in the past signal from the first memory and the data representing the object in the current signal from the buffer memory have different addresses. It should exist in . Therefore, if the signal processing means processes both of the signals, a movement trajectory signal representing an appropriate movement trajectory of the object to be searched can be obtained. [0023] Since the signal output from this signal processing means is written in the second memory at the address position determined by the specified display mode, the signal output from this second memory is written to the display device in the specified display mode. is displayed. [0024] The second radar device of the present invention has the following function (scan correlation processing) in addition to the function of the first radar device (displaying the movement trajectory of detected objects such as islands and other ships). be done.

[O○25] In other words, since the signal output from the correlation means is stored in the third memory at the address position corresponding to each point on the earth's surface where the echo signal occurred, changes in the distance traveled by the own ship and the course The data representing the fixed target in the current echo signal output from the buffer memory and the past echo signal output from the third memory will be written to the corresponding address. Therefore, even if there is data representing a fixed target in the past signal from the third memory, there is no data corresponding to the data representing the fixed target in the current signal from the buffer memory. The data representing fixed targets in the 3 memory is considered to be unnecessary waves due to reflection from the sea surface, etc. Therefore, by performing correlation processing on the re-output signal using the correlation means, it becomes possible to obtain data of only the necessary reflected waves from which unnecessary wave data has been removed. [0026] Furthermore, since the signal output from the correlation means is written in the second memory at the address position determined by the specified display mode, the signal output from this second memory is written to the display device in the specified display mode. Displayed by For example, if the display mode is TM-NU mode or RM-H
No matter which U mode is specified, for the third memory, data is always written to the storage element having the address determined by the TM-NU mode, and for the second memory, the specified display mode (TM/NU mode or R.M.
-HU mode) Data is written to the memory element having the write address determined by the HU mode. Therefore, if the scan correlation process is performed using the past data written to the third memory and the current data given from the buffer memory, the scan correlation process can be performed correctly regardless of the display mode. . [0027]

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 1, the same reference numerals as those shown in FIG. 7 of the conventional example refer to the same parts, parts, etc. [○028] The moving trajectory signal generation unit 4a converts the echo signal output from the buffer memory 3 into image display data and provides it to the frame memory 6 and the moving trajectory signal processing memory 8a. Based on the output signal from the output signal and the output signal from the movement trajectory signal processing memory 8a, for example, a movement trajectory signal that lasts only for a predetermined period of time, or a movement trajectory portion that indicates the current position of the ship when the movement trajectory is displayed, is A movement trajectory signal (a signal representing the movement trajectory of an object to be detected, such as an island or another ship) is generated by signal processing so that the older portions of the movement trajectory are displayed brightly and darkly. In this movement trajectory signal generation section 4a, among the signals output from the buffer memory 3, signal levels such as unnecessary reflected waves from sea surface reflections are low (for example, the maximum value is set to 10
In this case, ignore signals from O to 4) and use high signal levels (5 or higher) such as reflected waves from islands or other ships.
Only the signals of 1 and 2 are provided to the movement trajectory signal processing memory 8a. This process is performed because the display target of the movement trajectory is an island, another ship, or the like. [0029] The movement trajectory signal processing memory 8a always outputs the movement trajectory signal given from the movement trajectory signal generation unit 4a to the second light, regardless of whether the usage mode is, for example, TM-NU mode or RM-HU mode. The data is written into a memory element having a write address determined by the TM-NU mode given by the address generator 9. On the other hand, the frame memory 6 stores the movement trajectory signal given from the movement trajectory signal generation section 4a in a designated display mode (TM-NU mode or RM-H mode) given from the first write address generation section 5.
The data is written to a memory element having a write address determined by U mode). The data written in the frame memory 6 is read out based on the read address generated by the read address generation section 7 according to the rask scan method. The read data is displayed as an image on a display device such as a CRT (not shown). Note that the contents written to the moving trajectory signal processing memory 8a and the contents written to the frame memory 6 are almost the same as those shown in FIGS. 3, 4, and 5, which are cited in the explanation of the scan correlation processing below. . However, the display of the movement trajectory is not described. [0030] In this way, the write address for the movement trajectory signal processing memory 8a is always the write address determined by, for example, the TM-NU mode, regardless of the specified display mode, so that the write address for the movement trajectory signal processing memory 8a is always determined by, for example, the TM-NU mode. Correspondence between the past signal and the current signal from the buffer memory 3 can be established accurately. Therefore, even if the RM/HU mode is specified, the movement trajectory signal generation section 4a can properly generate the movement trajectory signal, and as a result, the RM-H
Even in U mode, the movement trajectory of objects to be detected, such as islands and other ships, can be properly displayed. [0031] FIG. 2 shows another embodiment of the present invention. In this embodiment, in addition to the function of the above embodiment (displaying the movement trajectory of the object to be detected), it is configured to perform scan correlation processing to remove unnecessary waves such as reflections from the sea surface. Note that scan correlation processing is a process for creating data for one rotation using, for example, received signals for 10 rotations of the antenna. To briefly explain, first, the echo signal of the first layer and the The second layer echo signal is compared to create comparison result data according to a certain rule, and then the comparison result data is compared with the third layer echo signal to create new comparison result data. After that, by sequentially repeating the same process as above, images caused by unstable reflections such as sea surface reflections are removed. That is, to perform scan correlation processing, the current echo signal and past echo signals are used. [0032] The write data creation unit 4 performs scan correlation processing based on the current echo signal given from the buffer memory 3 and the past echo signal read out from the processing memory 8, and converts it into data for image display. . The output data from the write data creation section 4 is transmitted to the second write address generation section 9.
is written into the storage element of the processing memory 8 with the write address generated by the first write address generator 5, and is written into the storage element of the frame memory 6 with the write address generated by the first write address generator 5. The data written in the frame memory 6 is read out based on the read address generated by the read address generation section 7 according to the rask scan method. The read data is displayed as an image on a display device such as a CRT (not shown). [0033]The second write address generation unit 9 for the processing memory 8 is configured to always generate a write address determined by the TM-NU main code, for example, from the output signal of the write data generation unit 4. "No. for frame memory 6"
The write address generation section 5 is configured to generate a write address determined by the display mode (for example, TM-NU mode or RM-HU mode) specified at each time based on the output signal of the write data generation section 4. . [0034] In other words, data is always written in the processing memory 8 to a memory element having a write address determined by the TM-NU mode, for example, and data is written to a memory element having a write address determined by the display mode at that time in the frame memory 6. Write the data. In other words, the data written to the frame memory 6 is the data written to the processing memory 8 plus the course θG. Other than this point, the data written to the processing memory 8 and the data written to the frame memory 6 are exactly the same, only that the contents of the processing memory 8 are rotated and written to the frame memory 6 when writing. [0035] Therefore, even when the RM-HU mode is specified, while data is always written to the processing memory 8 at the write address determined by the TM-NU mode, the past data in the processing memory 8 and the current data in the buffer memory 3 are Correspondence with data can be established accurately, and accurate scan correlation processing can be performed. [0036] The operation when the above two combination modes are specified will be described below. [0037] [When TM-NU mode is specified] Both the write address for the processing memory 8 and the write address for the frame memory 6 are set as write addresses determined by the TM-NU mode. Specifically, if the data in the processing memory 8 is as shown in FIG. 3(a), the data in the frame memory 6 is written in correspondence as shown in FIG. 4(a). Further, as the own ship moves, the data in the processing memory 8 changes from the state shown in FIG. 3(a) to the state shown in FIG. 3(b), for example.
When the state further changes sequentially to the state shown in FIG. 3(C), the data in the frame memory 6 sequentially changes from the state shown in FIG. 4(a) to the state shown in FIG. 4(b), and further to the state shown in FIG. 4(C). . In other words, the target is not affected by the movement of own ship, and the fixed target A~
C is fixed in the processing memory 8. When the contents of the frame memory 6 change from FIG. 4(b) to FIG. 4(C), a pullback operation is added, but since the scan correlation result is stored in the processing memory 8, there is no need to redo the scan correlation from the beginning. . Specifically, the contents of the frame memory 6 are updated with one rotation of the beam. [0038] [When RM-HU mode is specified] The write address for the processing memory 8 is the write address determined by the TM-NU mode, and the frame memory 6
The write address for is the write address determined by the RM-HU mode. Specifically, if the data in the processing memory 8 is as shown in FIG. 3(a), the data in the frame memory 6 is as shown in FIG. 5(a). Further, as the own ship moves, the data in the processing memory 8 changes from the state shown in FIG. 3(a) to the state shown in FIG.
When the state changes sequentially to the state shown in (C), the data in the frame memory 6 sequentially changes from the state shown in FIG. 5(a) to the state shown in FIG. 5(b), and further to the state shown in FIG. 5(C). That is, in this case as well, the fixed targets A to C in the processing memory 8 remain immobile. In this example, the data written to the frame memory 6 is the same as the content written to the processing memory 8, but rotated by the course θG, and the data written to the processing memory 8 and the data written to the frame memory 6 are exactly the same. , the contents of the processing memory 8 are rotated when writing to the frame memory 6. [0039] In this way, no matter which usage mode is specified, as the own ship moves, the data writing area (circular arc in the figure) is changed to the processing memory 8 based on the movement of the own ship. 8. Move the top. The process of moving the beam center address (own ship position) on the processing memory 8 due to the movement of the own ship will be briefly described below. For purposes of explanation, the course θ6 is assumed to be constant. [0040] When the X address of the processing memory 8 is composed of n bits, the beam center address changes due to movement of the own ship, but data extracted from the same n pits is always sufficient. That is,
For example, when n=4, all bits 1 (OFH) are followed by °'
IOH", but the lower 4 bits are extracted (OOH). Therefore, the X address in this case is OOH"~"
OFH", the phenomenon described below occurs. Such processing is performed by the second write address generation section 9. [0041] As shown in FIG. When the address is set to the P1 position, the next beam center address is moved from the bottom of the figure to the diagonally upper side of the P2 position, but when passing the upper end of the processing memory 8, the next beam center address is moved from the P position to the lower side along the Y axis of the figure. as shown by the dashed arrow.Furthermore, after moving from the P position to the P4 position, move from the P position to the P5 position on the left side along the X axis in the figure.Such a form As a result, the beam center address is sequentially changed.

Note that if the beam center address is located near the peripheral edge of the processing memory 8 as shown in FIG.
As explained with reference to FIG. 6, the writing position of this protruding portion is turned around and written to the lower end portion of the processing memory 8. In other words, if the arc-shaped writing area protrudes from the upper end of the processing memory 8, the protruding part is written by wrapping it to the lower end of the processing memory 8, and if it protrudes from the right end, the protruding part is moved to the left end. Make sure to write by wrapping the part. [0043] As described above, when specifying either the TM-NU mode or the RM-HU mode, the T
Since the data is written at the write address determined by the M-NU mode, the write position on the processing memory 8 is not affected by the turning or movement of the own ship, so it is possible to correctly correspond between past data and current data. When the beam center address to be written into the processing memory 8 is moved, the part protruding from the processing memory 8 is written by turning around, so that there is no loss of written data. As a result, in TM-NU mode, continuous scan correlation processing without interruption can be realized, while in RM-HU mode, scan correlation processing, which was previously impossible, can be executed correctly. .

[O○44] In the above embodiment, the reading for display on the display is performed using the rask scan method, and both the first write address generation section and the second write address generation section perform coordinate conversion from polar coordinates to rectangular coordinates. Although an example is given in which the address signal obtained by performing the above processing is applied to the frame memory and the processing memory, it is also possible to perform reading for display on a display using a spiral scan method. Even when using this spiral scan method, the second write address generation section generates a polar coordinate address signal,
Both the fourth write address generation section and the second write address generation section do not need to perform coordinate conversion from polar coordinates to rectangular coordinates. Furthermore, in each of the above embodiments, the echo signal was written into the processing memory using the write address in the TM-NU mode, but the invention is not limited to this, and in short, each point on the earth where the echo signal was generated is written. It is sufficient to write the data into the storage element of the corresponding processing memory. For example, the echo signal may be written to the processing memory at the write address in the TM-CU mode, and the same effect as the above embodiment can be obtained. [0045]

【Effect of the invention】

As explained above, according to the first radar device of the present invention (corresponding to claim 1), no matter what combination of specified display modes, objects to be detected such as islands or other ships can be detected. The movement trajectory can now be displayed properly. [0046] As explained above, according to the second radar device (corresponding to claim 2) of the present invention, in addition to the effects of the first radar device, the specified display mode can be used in any combination ( Even in TM-NO mode or RM-NO mode), it is possible to perform correct scan correlation processing, accurately remove unnecessary waves such as sea surface reflections, and accurately display the surrounding situation. play. [0047] The present invention is particularly effective in any of the radar devices described above when performing display when the own ship is moving or when the amount of movement of the own ship cannot be ignored.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram of a radar device according to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a radar device according to another embodiment of the present invention.

[Figure 3] FIG. 3 is a data map diagram showing changes in processing memory.

FIG. 4 is a data map diagram showing changes in the frame memory during TM-NU mode.

FIG. 5 is a data map diagram showing changes in the frame memory in the RM-HU mode.

FIG. 6 is a movement pattern diagram of the beam center address (own ship position) by scrolling.

[Figure 7] FIG. 1 is a configuration block diagram of a conventional radar device.

[Figure 8] FIG. 3 is a schematic diagram showing a display image in RM mode.

[Figure 9] FIG. 3 is a schematic diagram showing a display image in TM mode.

FIG. 101 is a schematic diagram showing a display image in NU mode. FIG. 111 is a schematic diagram showing a display image in HU mode. FIG. 12 is a schematic diagram showing a display image in CU mode. [Explanation of symbols] 1 Receiver 2 A/D conversion section 3 Buffer memory 4 Write data control section (correlation means) 5 First write address generation section 6
Frame memory (second memory) 7 Read address generation section 8 Processing memory (third memory) 9 Second write address generation section 4a Movement trajectory signal generation section (signal processing means) 8a Movement trajectory signal processing memory (first memory)

【Document name】

Claims (2)

[Claims] Claims 1. A radar device that receives returning echo signals by sequentially emitting detection signals in different directions and displays surrounding conditions in a wide range of directions on a display, comprising: a receiving unit that receives echo signals; a buffer memory for temporarily storing an echo signal caused by a detection signal sent from the unit; and a buffer memory for storing signals given from the following signal processing means at address positions corresponding to each point on the earth's surface where the echo signal occurred. A moving trajectory signal (from islands, other ships, etc.) obtained by signal processing the current echo signals from other ships, etc. output from the first memory and the buffer memory, and the past echo signals read from the first memory. a signal processing means for supplying a signal representing a movement trajectory of the detected object to a first memory and a second memory; and a second memory for storing a movement trajectory signal outputted from the signal processing means at an address position determined by a set display mode, respectively. A radar device comprising a memory and a display that displays a signal read from the second memory. 2. A radar device that receives returning echo signals by sequentially emitting detection signals in different directions and displays surrounding conditions in a wide range of directions on a display, comprising: a receiving unit that receives echo signals; a buffer memory for temporarily storing an echo signal caused by a detection signal sent from the unit; and a buffer memory for storing signals given from the following signal processing means at address positions corresponding to each point on the earth's surface where the echo signal occurred. A moving trajectory signal (from islands, other ships, etc.) obtained by signal processing the current echo signals from other ships, etc. output from the first memory and the buffer memory, and the past echo signals read from the first memory. a signal processing means for supplying a signal (representing a movement trajectory of a detected object) to a first memory and a second memory; 2 memories, a 3rd memory for storing signals given from the correlation means described below at address positions corresponding to respective points on the earth's surface where the echo signals have occurred, and a Correlation means for correlating and correlating the past echo signals read out from the third memory and providing the output signals to the third memory and the second memory; and a display device for displaying the signal read out from the second memory. A radar device characterized by: