Technical Field [0001] The present in-vention relates to a device that assists in 10 adjusting the orientation of an antenna. Background Art [0002] When installing a directional antenna, it is important to place it toward an appropriate direction in order to maximize the reception 15 level. Currently, when adjusting the antenna orientation, a worker seeks the orientation with the maximum reception level by a process of triai and error by changing the antenna orientation in a step-by-step manner and installs the antenna in that orientation. However, because two orientations, the elevation and the 20 azimuth, need to be set to adjust the antenna orientation, it is extremely difficult in practice to set the antenna orientation toward the direction in which the maximum reception level can be achieved. It is time-consuming work to set the antenna toward the direction with the maximum reception level in a step-by-step manner by making fine 25 adjustment of the elevation and the azimuth by checking the reception level each time. Since radio waves at millimeter-wave frequencies have been used recently, it is required to set the antenna orientation with respect to the wave source antenna with such accuracy as if going through the eye of a needle. For example, extremely fine angle 30 adjustment of 1.0° or less, such as 0.4° or 0.2**, is required today. In consideration of the case of mounting the antenna on a mast or the like using mounting bracket, it should take less than one turn of a mounting screw. Considerable experience is needed for accurate adjustment of the antenna orientation by trial and error without any criteria like an 3 5 i n d e X. 3 [0003] Methods for assisting in setting the antenna orientation toward the wave source direction are proposed (for example. Patent Iv i t e r a t u r e s 1, 2 a n d 3). 5 For example, Patent Literature 1 discloses a direction finder that searches for a radio emitting source. The direction finder includes a direction finding array antenna and a camera mounted on the array antenna. A lens of the camera is aligned so that its optical axis is substantially orthogonal to the vertical plane of the array antenna. 10 In this structure, an image of an object that is assumed to be a radio emitting source is taken by the camera. Further, a received signal that is received by the array antenna is visualized by a technique such as radio holography and output as a wave source image. Then, a screen, on which the camera image and the wave source image are displayed 15 and superimposed on one another, is provided to a worker. By viewing the screen, the worker can specify the object as the radio emitting source. [0004] In Patent Literatures 2 and 3, a camera that is aligned with 20 respect to an antenna is mounted on the antenna, and the camera is used as a sighting device. A radio emitting source is specified by the camera, and the orientation of the antenna is adjusted so that the radio emitting source comes at the center of the screen. In this manner, specifying the radio emitting source by the camera or using the camera 25 as the sighting device are helpful in adjusting the antenna orientation. Citation List Patent Literature [0005] PTLl: Japanese Unexamined Patent Application Publication No. 30 2007-33380 PTL2: Japanese Unexamined Patent Application Publication No. 2007-88576 P T~ L 3 : Japanese Lhi e x a m i n e d Patent Application Publication No. 2005-72780 4 Summary of invention Technical Problem [0006] 110wcVe 1-, iI is considei'ecl thai the techniques disclosed in 5 Patent Literatures 1 , 2 and 3 have the following problems. F'irst, it is not easy to align the optical axis of the camera toward the antenna reception direction with high accuracy. An alignment error needs to be 1.0° or less, and it is impossible to manually align the optical axis of the camera with the antenna 10 reception direction at the antenna installation site. Accordingly, an antenna manufacturer needs to manufacture and sell an antenna device with an aligned camera attached; however, attaching the camera to each antenna results in a considerable increase in costs. Second, such a camera needs to have a substantial zooming 15 feature. A large optical device is required to take an image of the radio emitting source at a distance of several hundred meters or several kilometers. This also causes a considerable increase in costs. Third, there is a problem that the radio emitting direction from the radio emitting source is not always vertical to the antenna plane of 20 the radio emitting source. When the radio emitting direction is deviated even slightly from the antenna plane, even if the antenna orientation is adjusted at the correct direction to the antenna plane of the radio emitting source, it is not necessarily the orientation where the maximum reception level is achieved. 25 [0007] An exemplary object of the present invention is to provide a device that can assists in adjusting the orientation of an antenna with high accuracy in a simple and inexpensive structure. Solution to Problem 30 [0008] An antenna orientation adjustment assistance device according to an exemplary aspect of the present invention includes a reception strength detection unit for detecting a reception strength of radio waves received by an antenna unit, a position calculation unit for 5 c a I c I! 1 a t i D g a r e 1 a t i \' e angle ]3 o s i t i o n o f I h e a lU e n n a unit b y u sing a n image taken by a camera fixed relative to the antenna unit, and a reception strength recording unit for recording the relative angle ]30siIi 0n 0f the antenna unit and the reception strength at the relative 5 angle position in association with each other. [0009] An antenna orientation adjustment assistance program according to an exemplary aspect of the present invention causes a computer to function as a reception strength detection unit for detecting a reception 10 strength of radio waves received by an antenna unit, a position calculation unit for calculating a relative angle position of the antenna unit by using an image taken by a camera fixed relative to the antenna unit, and a reception strength recording unit for recording the relative angle position of the antenna unit and the reception strength at the 15 relative angle position in association with each other. [0010] A nonvolatile recording medium according to an exemplary aspect of the present invention stores the antenna orientation adjustment assistance program in a computer-readable manner. 20 [0011] An antenna device installation method according to an exemplary aspect of the present invention includes a step of temporarily installing an antenna device, a step of mounting a camera on the antenna device so that a position and an orientation are not 25 displaced relative to an antenna unit of the antenna device, a position calculation step of calculating a relative angle position of the antenna unit by using an image taken by the camera, a reception strength detection step of detecting a reception strength of radio waves received by the antenna unit, and a reception strength recording step of 30 recording the relative angle position of the antenna unit and the reception strength at the relative angle position in association with each other, wherein the position calculation step, the reception strength detection step and the reception strength recording step are repeated by changing an orientation of the antenna unit. 6 Advantageous Effects of Invention [0012] According Io the exemplary aspects of the ]3resent invention, any worker can quiclcly and accurately install an antenna device. 5 Brief Description of Drawings [0013] Fig. 1 is a view showing the installation work of an antenna device according to a first exemplary embodiment. Fig. 2 is a view showing the case where a camera is fixed to an 10 antenna unit using a m o u n t i n g j i g. Fig. 3 is a functional block diagram of an antenna orientation adjustment assistance system. Fig. 4 is a flowchart showing a procedure of adjusting the orientation of the antenna unit to the most appropriate direction. 15 Fig. 5 is a flowchart showing a detailed procedure ofa step of searching for the best reception direction. Fig. 6 is a view showing the antenna device viewed from above. Fig. 7 is a view showing an example of a captured image. Fig. 8 is a view showing an example of a display screen. 20 Fig. 9 is a view showing the state where the azimuth of the antenna unit is slightly shifted. Fig. 10 is a view showing an example of a captured image. Fig. 11 is a view showing the state where a current image is superimposed on an initial image. 25 Fig. 12 is a view showing a gap between a current image and an initial image. Fig. 13 is a view showing an example of radio emission patterns from an opposite antenna and a step-by-step change of the antenna orientation in accordance with those patterns. 30 Fig. 14A is a graph showing a change in reception strength with a change in the orientation of the antenna unit. Fig. 14B is a graph showing a change in reception strength with a change i 1:1 the 0 }■ i e n t a t i 0 n 0 f t h e a 311 e n n a unit. 7 1' i g. ] 4 C is a graph s h o \v i n g a change in reception s t r e n g UT W i I IT a change in t li e o r i e n I a t i o n o f t he ante n n a unit. Fig. 15 is a detailed flowchart of a step of adjusting the orientation of the antenna unit. 5 f' ig. 16 is a view showing a gap between a current position and a peak position. Description of Embodiments [0014] Exemplary embodiments of the present invention are illustrated 10 in the drawings and described hereinafter by referring to the reference symbols of elements in the drawings. (First exemplary embodiment) A first exemplary embodiment of the invention is described hereinafter. 15 Fig- 1 is a view showing the installation work of an antenna device 100 according to this exemplary embodiment. A known antenna device can be used. Although a so-called parabolic antenna is shown as an example, the type of the antenna is not particularly limited in the application of this exemplary embodiment. 20 [0015] The structure of an antenna device 100, though it is already known, is briefly described hereinafter. Fig. 1 shows the antenna device 100 mounted on a mast 10 and viewed from the back. 25 The antenna device 100 includes an antenna unit 110, a transmitting and receiving unit 120, and a mounting means 130. The transmitting and receiving unit 120 is an electrical circuit unit that includes a receiving circuit 121 and a transmitting circuit 122 (see Fig. 3) and performs modulation and demodulation of signals 3 0 according to the need. 1^ h e transmitting and receiving unit 120 includes a storage box 123 that serves as a housing and electrical circuit units (121, 122) stored in the storage box 123, and it is coupled to the backside of the antenna unit 110. The backside of the antenna unit 110 and the 8 1 ra)ismi11 ing anci receiving unit ) 20 arc coupled by a coupling mechanism (not shown), 1 hongh not illustrated in detail. [0016] The mounting means 130 installs and fixes the antenna unit 110 5 and the transmitting and receiving unit 120. The case where the mounting means 130 fixes the antenna unit 110 and the transmitting and receiving unit 120 to the mast 10 is shown as an example. The mounting means 130 includes a clamp means 140 and an 10 elevation adjustment fitting 150. The clamp means 140 includes a holding member 141 and a receiving member 142 that holds the mast 10 tight on both sides. The both members are coupled by a fastening bolt 143. When the holding member 141 and the receiving member 142 hold the mast 10 light on 15 both sides, the orientation (azimuth) of the antenna unit 110 can be adjusted by adjusting the orientation (azimuth) of the receiving member 142. Further, by adjusting the gap between the holding member 141 and the receiving member 142 by turning the fastening bolt 143, the orientation (azimuth) of the antenna unit 110 can be 20 adjusted about the mast 10 as the center of rotation. [0017] The elevation adjustment fitting 150 couples the antenna unit 110 and the transmitting and receiving unit 120 to the clamp means 140, allowing adjustment of the elevation of the antenna unit 110. The 25 elevation adjustment fitting 150 is fixed to the receiving member 142 on its base end side (151) and fixed to the backside of the antenna unit 110 on its leading end side. (Note that, in Fig. 1, the leading end side of the elevation adjustment fitting 150 is hidden behind the storage box 123.) 30 The base end side (151) oft he elevation adjustment fitting 150 has several long holes 152, and the elevation adjustment fitting 150 is secured to the receiving member 142 by mounting screws 153 that are inserted through the long holes 152. 9 The base end 15) of the elevation adjustment fitting 150 is provided with an adjusting screw 154 that hangs down substantial iy vertically, and the adjusting screw 154 is screwed also to the receiving member 142. By turning to move the adjusting screw 154 forward or 5 backward, the base end 151 of the elevation adjustment fitting 150 rotates relative to the receiving member 142 about the mounting screw 153 as an axis. Thus, the elevation of the antenna unit 110 can be adjusted by turning the adjusting screw 154. [0018] 10 An antenna orientation adjustment assistance system according to this exemplary embodiment is described hereinbelow. The hardware configuration of the antenna orientation adjustment assistance system at least includes a camera 200 and a PC (Personal Computer) 300 as shown in Fig. 1. 15 The camera 200 may be a digital camera or a portable terminal (for example, a mobile phone) with a camera function. In Fig. 1, the camera 200 is mounted on the back of the antenna unit 110, and the direction in which the lens of the camera 200 takes an image has no relation with the direction in which the antenna device 100 receives 20 radio waves. Like in this example, the direction in which the camera 200 takes an image is arbitrary. Note that, however, as will be apparent from the following description, an object whose position is set (fixed) needs be within an imaging region. In other words, an imaging direction to merely take a 25 sky image, for example, is of no use. It is preferred that a construct such as a building or a house, for example, appears in the image. Further, if possible, it is more preferred that an object with a clear color, shape or the like appears in the image. A worker who installs the antenna device 100 looks over the surroundings and roughly 30 determines the orientation of the camera 200 so that the above-described construct appears in the image. Then, the worker fixedly mounts the camera 200 on an appropriate position of the antenna device 100. [0019] 10 In the case of mounting the camera 200 on the top surface of the storage box 123 as shown in ]"ig. 1 , tlic easiest way is to attach tlie camera 20 0 to the storage box 123 using a double-stick tape. Note that, however, even when the easiest way is employed, it is necessary 5 thai the positions and orientations of the antenna unit 110 and the camera 200 are not displaced relative to each other. Stated differently, if the position or orientation of the antenna unit 110 changes, the position or orientation of the camera 200 should change in the same way. 10 [0020] Fig. 2 shows, for reference, the case where the camera 200 is fixed to the antenna unit 110 using a given mounting jig 220. Like in this example, the camera 200 can face the same direction as the reception direction of the antenna unit 110 as a matter of course. 15 [0021] The PC 300 may be any computer as long as it includes a memory and a CPU and can implement specified processing functions by loading a program, and it may be a portable small computer, for example. 20 For example, the PC 300 may be a notebook PC. Although it is called by various names such as a notebook computer, a laptop, a palmtop and an Ultrabook, such a difference in name is nothing to do with the gist of the present invention as a matter of course. Further, the PC 300 may be a recent tablet terminal, smartphone or the like. 25 [0022] Fig. 3 is a functional block diagram of the antenna orientation adjustment assistance system. In Fig. 3, a processing unit 400 is a functional unit that is implemented when a CPU of 1 he PC 300 loads a program. 30 The processing unit 400 includes an image processing unit 410, a reception strength detection unit 420, a reception strength recording unit 430, a peak search unit 440, and an adjustment instruction unit 450. n Further, Ihc image proeessing unil 4)0 inekides an image ca]:)tIIre unit 411, an initial image recording unit 412, an image matching processing unit 413, and a displacement calculation unit (position calculation unit) 414. 5 The adjustment instruction unit 450 includes a peak position 1' e c 0 r d i n g unit 451 and a gap calculation unit 452. The detailed operation of each functional unit is described later with reference to the flowchart and the illustration. [0023] 10 Fig. 4 is a flowchart showing a procedure of adjusting the antenna orientation to the most appropriate direction. The antenna orientation adjustment method broadly includes a preparation step (STIOO), a step of searching for the best reception direction (ST200) and a step of adjusting the antenna orientation 15 (ST300). Each step is described hereinbelow. [0024] The preparation step (STIOO) includes a step of temporarily installing the antenna device 100 (ST 110), a step of mounting the 20 camera 200 on the antenna device 100 (ST120), a stepof wiring (ST130), and a step of starting the PC 300 (ST140). [0025] The step of temporarily installing the antenna device 100 (ST 110) is a step of installing the antenna device 100 at a specified 25 installation place using the mounting means 130 as already shown in Fig. 1. In this step, the orientation of the antenna unit 110 may be adjusted roughly to a certain azimuth and elevation. For example, the orientation of the antenna unit 110 may be set toward an opposite 30 station using a compass (an azimuth magnet), or the orientation of the antenna unit 110 may be set to an opposite station after identifying the opposite station using a telescope. Note that, although fine adjustment will be made later (ST300), because it makes the fine adjustment difficult ifthere is a gap of as I 12 large as 10° or 2 0°, the gap is preferably within the range of about 5°, front and back, for example, with respect to the direction that is assumed to be the best. [0026] 5 The step o f m o u n t i n g the camera 200 (S '1' 120)isalsoas described earlier with reference to Fig. 1. A worker looks over the surroundings and roughly determines the orientation o f t h e camera 200 so that a construct appears in the image if possible, and then fixedly mounts the camera 200 on an appropriate position of the antenna 10 device 100. [0027] Then, wires are connected to the PC 300. Specifically, the camera 200 and the PC 300 are connected first. Then, wiring is done so that the reception level of the antenna device 100 can be detected 15 by the PC 300. To be specific, the receiving circuit 121 of the transmitting and receiving unit 120 is connected to the PC 300. [0028] Although an example where the camera 200 and the antenna device 100 are connected to the PC 300 by wire is shown in Fig. 1, 20 they may be connected wirelessly. [0029] After wiring is done, the PC 300 is started (ST140), and a specified program (antenna orientation adjustment assistance program) is loaded. The preparation step (STIOO) thereby ends. 25 [0030] Next, the step of searching for the best reception direction (ST200) is described. Fig. 5 is a flowchart showing a detailed procedure of the step of searching for the best reception direction (ST200). 30 The first to be performed is the capture of an initial image. The camera 200 is already mounted on the antenna device 100, and a worker captures the current image in the caniera 200 as an initial image (SI'310). Fig. 6 is a view showing the antenna device 100 viewed from above. 13 (Stated differently, Fig. 6 is a view showing the antenna device 100 viewed from the direction of the arrow VI in Fig. 1.) In Fig. 6, the imaging range of tlie camera 200 is indicated by the dotted line. (Note that the alternate long and short dashed line 5 indicates the center line of the imaging range.) In the example of Fig. 6, it is assumed that a building 20 stands near the center of the imaging range of the camera 200. Accordingly, the building 20 appears near the center in the camera image as shown in Fig. 7. The camera image is displayed on a display unit 310 of the 10 PC 300 through the image capture unit 411. [003 1] Fig. 8 is a view showing an example of a display screen. The display screen is largely divided into four regions, and the upper left region is an initial image display region RIO that displays the initial 15 image. A worker views the image displayed in the initial image display region RIO and recognizes that an object (20) that can serve as a landmark appears in the image and then presses a record button 341 below the image. (The worker may click on the record button 341 by moving a 20 pointer on the screen using a mouse or may directly press the record button 341 with a finger if the display unit 310 is a touch panel. Such a user interface may vary in design.) The initial image is recorded and stored into the initial image recording unit 412. 25 [0032] After capturing the initial image (ST310), the worker conducts work to slightly change the orientation of the antenna unit 110 (ST320). Fig. 9 is a view showing the state where the azimuth of the 3 0 a n t e n n a u n i t 1 1 0 i s s 1 i g h 11 y s h i f t e d. (Although the azimuth is shifted about 10° in Fig. 9 to facilitate understanding for convenience of explanation, it Is preferred in practice to shift the angle little by little.) i ! 14 Because Ilie camera 200 is displaced in 1 egi'a 11 y with the antenna unit 1 10, the azimutli o f the camera 200 also changes in the same way as the antenna unit 110. Accordingly, the imaging direction of the camera 200 changes. As a result, it is assumed that the building 20 is 5 displaced slightly to the 1 ei't in the imaging region as shown in Fig. 10. In the display screen of l^Mg. 8, iI is assumed that the region below the initial image display region RIO is a current image display region R20 that displays the current image. With the current image display region R20, the worker can view the image that is currently captured by the 10 camera 200 in real time. [0033] The image that is taken by the camera 200 after its orientation is changed is the current image. The current image is captured by the image capture unit 411 (ST330). Then, the image processing unit 410 15 compares the current image with the initial image and thereby calculates a gap between the current image and the initial image (ST340). Comparing two images and recognizing the images to see how much one is deviated from the other is an application of pattern matching and implemented by various methods. For example, Phase- 20 Only Correlation is known. [0034] The image matching processing unit 413 compares the initial image PIO with the current image P20 and shifts the current image P20 so that the current image P20 matches the most with the initial image 25 PIO. Fig. 1 1 is a view showing the state where the current image P20 is superimposed on the initial image PIG so that they match. It is assurned that the building 20, which has appeared near the center in the initial image PIO, appears leftward in the current image P20. In this case, it is found that the image center Oc of the current image P20 is 30 displaced to the right relative to the image center Oi of the initial i m a g e P 1 0. [0035] i 15 T he (H s p 1 a c e m e n t c a 1 c i! 1 a I i o n u n i I 414 calculates 1 ii e g a ]T between the current image P20 and the initial image P 1 0 based on a result of matching by the image matching processing unit 413 (ST340). In this example, it is calculated how many pixels are left as a 5 gap. As shown in Fig. 12, it is assumed that the crosswise direction is the X-axis direction and the lengthwise direction is the y-axis direction in the display image. The displacement calculation unit 414 calculates the gap by calculating how many (AX) pixels in the x-10 direction and how many (AY) pixels in the y~direction the current imageP20isdeviatedfromtheinitialimageP10. The calculated gaps (AX, AY) are displayed on the display screen. It is assumed that the gaps in the x-direction and in the y-direction are displayed below the current image display region R20 15 (see Fig. 8). In this example, despite that the worker has intended to shift the azimuth (x-direction) only, the elevation (y-direction) has also been shifted slightly. In this manner, the image matching can detect a slight gap that cannot be recognized by the feeling of a finger or visual inspection of the worker. 20 [0036] As is understood from Fig. 11 or 12, when the center Oi of the initial image PIO is the origin of the coordinate system, the coordinates of the center Oc of the current image P20 is represented as (AX, AY). Accordingly, in this specification, the coordinates (AX, 25 AY) are referred to as the position of the current image P20 in some cases. Further, as described earlier, the positions and orientations of the antenna unit 110 and the camera 200 are fixed relative to each other. In other words, the orientation of the antenna unit 110 and the image taken by the camera 200 at the same orientation of the antenna 30 unit 110 are in one-to-one correspondence. Accordingly, in this specification, the coordinates (AX, AY) are referred to as the position of the antenna unit, equating the orientation (angle) of the antenna unit 110 with the position (AX, AY) of 1 he image in sonie cases. 16 (Thus, the displacement ealculation unit 414 is referred to as a p 0 s i t i 0 n c a I c u 1 a I i 0 n Li n i t i n s 0 m e c a s e s.) [0037] AfIer the position of the current image P20 is calculated in this 5 way, the reception strength is detected (ST350). Specifically, the strength of the signal that can be received in the current orientation of the antenna unit 110 is detected. The electric wave signal received by the antenna unit 110 is transmitted to the rece]?tion strength detection unit 420 through the transmitting and receiving unit 120 (the receiving 10 circuit 121). The reception strengtli detection unit 420 obtains the input signal level. The reception strength obtained in this manner is displayedonthedisplayscreen. It is assumed in this example that the display region of the reception strength, together with the gap, is placed below the current 15 image display region R20. [0038] The worker sees the position of the current image P20 and that the reception level at the position is obtained and then presses the record button 342. Then, the position of the current image P20 and the 20 reception level at this time are recorded as a pair (ST360). Specifically, when the worker presses the record button 342, the position of the current image P20 calculated by the displacement calculation unit 414 and the reception strength detected by the reception strength detection unit 420 are transmitted to the reception 25 strength recording unit 430. The reception strength recording unit 430 records the position of the current image P20 and the reception strength as a pair. [0039] Further, after the position of the current image P20 and the 30 reception strength are recorded, they are displayed as a graph on the display screen. It is assumed in this example that the upper right region of the display screen is a graph display region R30. [0040] 17 The worker repeals the steps from ehanging the antenna orientation (S'1^3 2 0) to recording the data (ST3 60) by ehanging the orientation of the antenna unit 110 little l:>y little. Fig. 13 shows an example o 1' the reception antenna }:ia11ern 30 5 and a step-by-slep change oi'the antenna orientation. In the case where the antenna unit 110 is a parabolic antenna, the reception antenna pattern 30 is a concentric circle. As the frequency of radio waves is higher, the orientation of the antenna unit 110 should be set toward the opposite station so as to align a point with a point. 10 [0041] The worker tries to change the orientation of the antenna unit 110 in various ways toward the rough direction from which radio waves are expected to come. For example, as indicated by the arrow A, the elevation is fixed 15 to a certain value, and only the azimuth is shifted from left to right. Next, as indicated by the arrow B, the elevation is changed to a little smaller value, and only the azimuth is shifted from right to left. Repeating this process, the orientation of the antenna unit 110 is changed as indicated by the arrow C and the arrow D. 20 By this operation, the graph indicating the relationship between the position of the antenna unit 1 10 and the reception strength is obtained. [0042] Fig. 14A is a graph showing a change in reception strength with 25 a change in the orientation of the antenna unit 110 along the arrow A. In Fig. 14A, the vertical axis is the reception level, and the horizontal axis is the azimuth. Note that the azimuth is represented by the value of AX. Further, because the elevation corresponds to Ay, Fig. 14A is labeled AYA on the right. Likewise, Fig. 14B is the graph 3 0 corresponding to the arrow B, and Fig. 1 4C is the graph corresponding t o t h e a r r o w C. The reception strength reaches its peak when going through the center of the emission pattern as indicated by the arrow C. '; [0043] i 18 The graphs of Figs. 14A, I4B and 14C arc displayed in the graph display region R30 of the display screen as shown in Fig. 8. The w0r]tion sIrength obtained by the ]:>eak search nieans as a peak position; and a gap calculation means for calculating a gap between a current 5 angle position o i' I h e antenna unit and the peak position. 5. The antenna orientation adjustment assistance device according to Claim 4, further comprising: a display means for displaying the gap calculated by the gap 10 calculation means. 6. A computer-readable nonvolatile recording medium storing an antenna orientation adjustment assistance program causing a computer to funotion as: 15 a reception strength detection means for detecting a reception strength of radio waves received by an antenna unit; a position calculation means for calculating a relative angle position of the antenna unit by using an image taken by a camera fixed relative to the antenna unit; and 20 a reception strength recording means for recording the relative angle position of the antenna unit and the reception strength at the relative angle position in association with each other. 7. An antenna device installation method comprising: 25 a step of temporarily installing an antenna device; a step of mounting a camera on the antenna device so that a position and an orientation are not displaced relative to an antenna ; unit of the antenna device; a position calculation step of calculating a relative angle 30 position of the antenna unit by using an image taken by the camera; a reception strength detection step of detecting a reception strength of radio waves received by the antenna unit; and a reception strength recording step of recording the i"e 1 ativc angle position of the antenna unit and t li e r c c e p I i o n strength a I the relative angle ]3osition in association with each other, wherein the position calculation step, the reception strength detection 5 step and the reception strength recording step are repeated by changing an orientation of the antenna unit. 8. The antenna device installation method according to Claim 7, further comprising; 10 a peak search step of searching for a maximum value of the reception strength among data recorded in the reception strength recording step; a peak position recording step of recording an angle position of the antenna unit corresponding to a maximum reception strength 15 obtained in the peak search step as a peak position; a gap calculation step of calculating a gap between a current angle position of the antenna unit and the peak position; and a step of adjusting an orientation of the antenna unit by checking the gap so as to set the orientation of the antenna unit at the 20 peak position.