WO2024092319A1

WO2024092319A1 - A structural displacement monitoring system

Info

Publication number: WO2024092319A1
Application number: PCT/AU2023/051111
Authority: WO
Inventors: Robert Young
Original assignee: Ravenco Pty Ltd
Current assignee: Ravenco Pty Ltd
Priority date: 2022-11-04
Filing date: 2023-11-03
Publication date: 2024-05-10
Anticipated expiration: 2025-05-04
Also published as: AU2023327764B2; GB202506670D0; AU2023327764A1

Abstract

A whole house structural displacement monitoring system automatically tracks real - time changes in floor, wall, and ceiling levels in multi-room houses where line-of-sight targeting is not feasible throughout the entire building. The system uses light emitters to focus beams of light on target surfaces and a control system to measure relative displacement by observing the offset of incident light on these surfaces. During setup, the control system is programmed to accommodate different room configurations with both line-of-sight and non-line-of-sight pairs of light emitters and target surfaces, allowing it to accurately measure the displacement of various structures within the adjoining rooms. This system provides a versatile and reliable solution for monitoring structural changes in residential buildings, even when direct line-of-sight is obstructed.

Description

A structural displacement monitoring system

Field of the Invention

[0001 ] This invention relates generally to an automated structural displacement monitoring system configured for periodically and automatically taking measurements over a long time period to detect structural displacement such as from floor heave or subsidence.

Background of the Invention

[0002] Building structural movement can result from various factors, including shifts in the foundation. For instance, reactive clay soil, a dense material, undergoes volume changes as it absorbs or releases moisture. When exposed to wet conditions, reactive clay absorbs moisture, expanding and causing slab heave. Conversely, in dry periods, it releases moisture and contracts, leading to slab subsidence.

[0003] These fluctuations can result in structural issues like cracked walls and instability, necessitating the need for monitoring.

[0004] Traditionally, structural movement is assessed through periodic surveys, often every six months, using conventional survey equipment to track changes in reference points. However, this manual approach is costly, time-intensive, and may yield inaccuracies.

[0005] As such, automated structural movement detection systems are preferable to manual surveying.

[0006] CN 21 1 147642 U (Ding et. al.) 31 July 2020 which discloses an automated monitoring system which designed to monitor the settlement value of objects like large buildings or steel frame structures. The system uses laser emitting monitoring components and plumb-bob connectors which hangs the monitoring components in a plumb position to ensure that the laser remains parallel even when the monitoring component is at different heights. If the object being measured settles, the laser emitter moves vertically, and the displacement of the laser can be used to calculate the settlement value. [0007] With reference to Figure 2, Ding et. al. anticipates using a cascade of monitoring components in series to measure displacement at multiple monitoring points along a structure. Specifically, Ding et. al. anticipates emitting a laser from a fixed reference point, such as a surrounding building which is unlikely to move. As such, displacement increments or decrements calculated between each successive pairs of monitoring devices can be used to calculate settlement values at each monitoring device along the structure with reference to the fixed reference point.

[0008] However, the arrangement taught by Ding et. al. is not suited for residential application, and the plumb-bob line-of-sight cascade configuration is especially difficult for self-installation by homeowners and the like. Moreover, dividing walls and other structures separating rooms of a residential home prevent the line-of-sight cascaded targeting taught by Ding et. al.

[0009] The present invention seeks to provide a way, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[0010] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Disclosure

[001 1 ] There is provided herein a whole house structural displacement monitoring system that automatically tracks real-time (such as daily) changes in floor, wall, and ceiling levels in multi-room houses where line-of-sight targeting is not feasible throughout the entire building.

[0012] The system uses light emitters to focus beams of light on target surfaces and a control system to measure relative displacement by observing the offset of incident light on these surfaces.

[0013] During setup, the control system is programmed to accommodate different room configurations with both line-of-sight and non-line-of-sight pairs of light emitters and target surfaces, allowing it to accurately measure the displacement of various structures within the adjoining rooms. This system provides a versatile and reliable solution for monitoring structural changes in residential buildings, even when direct line-of-sight is obstructed.

[0014] Specifically, the system comprises light emitters configured to emit a focused beam of light onto respective target surfaces. The system is configured to visibly ascertain target surface light incident offset to measure relative displacement.

[0015] These target surfaces may be defined by active light receiver modules or passive reference markers (such as marked stickers) attached to structural elements. [0016] During initial setup and programming, the control system can be programmed according to a multi-room configuration of a residential building, such as by way of a web-based graphical user interface. Specifically, the control system can be configured with line-of-sight pairs of light emitters in each room.

[0017] The controller can be further programmed with non-line-of-sight pairs of light emitters and target surface attached to opposite sides of a dividing structural element between adjoining rooms.

[0018] For example, a dining room of a home may be separated from a bedroom by an intervening wall. Line-of-sight emitters and target surfaces can be installed in each of the dining room and the bedroom, and the controller programmed accordingly via the web interface. The non-line-of-sight pairs of light emitters and target surfaces can be installed on opposite sides of the dividing wall intervening the bedroom and the bathroom. For example, a light emitter can be installed on one side of the wall and a target surface installed on an opposite side of the wall, each in line-of-sight with a respective target surface or light emitter in each room. Alternatively, a pair of light emitters or a pair of target surfaces may be installed on each side of the wall.

[0019] As such, the controller is configured to measure target surface light incident offset in each room using the line-of-sight pairs.

[0020] For adjoining rooms, the controller is able to accurately measure displacement of the three structural elements separating the adjoining rooms independently.

[0021 ] Specifically, in accordance with the programming, the controller can detect displacement of a structural element in the first room when detecting target surface light incident offset in the first room only, detect displacement of a structural element in the second room when detecting target surface light incident offset in the second room only, and detect displacement of the dividing structural element when detecting target surface light incident offset in both of the adjoining rooms. In embodiments, the system can also detect simultaneous movement in more than one structural element.

[0022] In other words, according to the prohramming, the controller may be able to accurately measure displacement of a far wall (i.e., away from the dividing wall) in the dining room or in the bedroom when detecting displacement between one respective line-of-sight pairs only.

[0023] However, the controller can also accurately determine displacement of the intervening wall between the bedroom and the bathroom.

[0024] In contradistinction to the arrangement taught by Ding et. aL, the present system allows for whole multi-room building monitoring using the combination of the line-of-sight pairs of light emitters and non-line-of-sight pairs of light emitters which can be easily self-installed by homeowners. Furthermore, as opposed to installation of delicate plumb bob line cascade arrangements taught by Ding et. al. the homeowner can configure any multiroom set up just by programming the system with the line-of-sight pairs and non-line-of-sight pairs. Moreover, the present system does not require a fixed reference points as required by Ding et. al.

[0025] The present system may comprise relatively inexpensive componentry which can be mailed out to homeowners for self-installation by simply attaching light emitters and target services on walls for insurance warranty claims and the like and wherein any multiroom configuration can be measured by the user configuring the system with the line-of-sight pairs and the non-line-of-sight pairs accordingly without having to visually align transmitters and receivers across the entire building .

[0026] Other aspects of the invention are also disclosed.

Brief Description of the Drawings

[0027] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: [0028] Figures 1 - 4 show an optical receiver module of a floor level survey monitoring system in accordance with an embodiment

[0029] Figures 5 and 6 show a light emitter of the system according to embodiments; [0030] Figure 7 - 1 1 illustrates various installation techniques of the modules in accordance with embodiments;

[0031 ] Figure 12 illustrates an optical reference sticker used by the system in an embodiment;

[0032] Figures 13 and 15 illustrate pairing of modules to measure floor movement across a number of tiers which are not in line-of-sight with each other;

[0033] Figure 14 illustrates installation of a light emitter detected by two receiver modules;

[0034] Figure 16 illustrates an exemplary graphical user interface generated by the system in an embodiment;

[0035] Figure 17 shows a schematic of the floor level survey monitoring system;

[0036] Figure 18 shows a schematic of the light emitter in accordance with an embodiment;

[0037] Figure 19 shows a schematic of the receiver model in accordance with an embodiment;

[0038] Figure 20 shows exemplary incidence position measurement of the receiver module;

[0039] Figure 21 illustrates long-term trending generated by the system in an embodiment;

[0040] Figure 22 illustrates exemplary displacement trends measured in adjoining rooms.

Description of Embodiments

[0041 ] Figure 17 shows a structural displacement monitoring system 100 comprising a light emitter 101 . The light emitter 101 is configured to emit a focused beam of light. In the embodiment shown in Figure 18, the light emitter 101 comprises a laser transmitter 102 which is configured to emit a focused beam of light 103 towards a target surface. [0042] In one embodiment, the target surface is that of an optical receiver module 104 shown in further detail in Figure 19 installed within line-of-sight of the light emitter 101. In alternative embodiments, the target surface is that of a marked reference marker 136 which may be attached to a wall 136 or the like.

[0043] The optical receiver module 104 comprises a camera 105 and a controller 106 operably coupled thereto. The controller 106 is configured to periodically (such as daily) measure incidence positions 107 (shown in Figures 1 - 3) over a long time period, such as six months or more. The system 100 may use these incidence positions 107 to calculate a long-term floor level movement offset which is either positive (i.e., heave) or negative (i.e. subsidence).

[0044] The modules 101 , 104 may comprise data interfaces 108 for sending and receiving data across a wide area network 109, such as the Internet. Figure 17 shows wherein the modules 101 , 104 are in operable communication with a server 1 10 acting as a control system. The modules 101 , 104 may be configured for receiving configuration settings from the server 1 10 and transmitting measurements to the server 1 10.

[0045] With reference to Figures 18 and 19, the modules 101 , 104 may comprise a processor 1 1 1 for processing digital data. A storage device 1 12 in operable communication with the processor 1 1 1 across a system bus 1 13 is configured for storing digital data including computer program code instructions. In use, the processor 1 1 1 fetches these computer program code instructions and associated data for implementing the computational functionality described herein.

[0046] The processor 1 1 1 may be a low-power microcontroller, such as a PIC microcontroller or the like and wherein the storage 1 12 may be firmware-based.

[0047] The computer program code instructions may be logically divided into a plurality of computer program code instruction controllers 1 14.

[0048] Each module 101 , 104 may comprise settings 1 15 configured for controlling the operation thereof.

[0049] With reference to Figure 8, the light emitter 101 may comprise a transmission controller 1 16 operably coupled to the laser transmitter 102 to cause the laser transmitter 102 to transmit the beam of light 103. The transmission controller 1 16 may be configured to schedule the transmission of the beam of light 103.

[0050] The controllers 1 14 of the light emitter 101 may further comprise a server interface controller 1 17 which is configured for interfacing with the server 1 10. In embodiments, the server interface controller 1 17 may receive a transmission schedule from the server 1 10 which is stored within the settings 1 15. As such, the transmission controller 1 16 may control the periodic transmission of the beam of light

103 according to the transmission schedule, such as during the early hours of the morning.

[0051 ] With reference to Figure 19, the controllers 1 14 of the optical receiver module

104 may comprise an optical interpretation controller 106 in operable communication with the camera 105. The optical interpretation controller 106 is configured for measuring the incidence positions 107 by analysing image data captured by the camera 105.

[0052] The controllers 1 14 may further comprise a data logging controller 1 18 which may be configured for storing the measured incidence positions 107.

[0053] The optical receiver module 104 may further comprise a server interface controller 1 17. A server interface controller 1 17 may be configured for transmitting the measured incidence positions 107 to the server 1 10.

[0054] In embodiments, the optical receiver module 104 transmits the measured incidence positions 107 to the server 1 10 where the server 1 10 calculates the total floor level movement offset over a long time period. Alternatively, the optical interpretation controller 106 may calculate the total floor level movement offset according to the measured incidence positions 107.

[0055] The server interface controller 1 17 of the optical receiver module 104 may further receive a measurement schedule from the server 1 10 which is synchronised with the aforedescribed transmission schedule of the light emitter 101 . As such, the measurement by the optical receiver module 104 may be synchronised with the transmission of the beam of light 103 by the light emitter 101 . [0056] To save power and allow for measurement of a long time periods, modules 101 , 104 may default to a sleep state but which may periodically wake from the sleep state according to the configured transmission and measurement schedules for the respective transmissions of the beam of light 103 and the recording of the incidence position thereof.

[0057] The settings 1 15 may comprise wireless access point credentials to allow the modules 101 , 104 to connect to a home Wi-Fi router.

[0058] Figures 1 - 4 show the optical receiver module 104 in accordance with an embodiment wherein the module 104 comprises a housing 1 19 containing the camera 105 and a microprocessor circuit board 120 therein. The housing 1 19 may contain a battery 121 which preferably has sufficient capacity to operate the optical receiver module 104 for more than six months.

[0059] The camera 105 may be spaced away from an incidence screen 122 by an offset 123. The incidence screen 122 defines the target surface of the optical receiver module 104. The incidence screen 122 is within the field of view of the camera 105.

[0060] As such, the camera 105 is able to measure the incidence position 107 by the respective position of the incidence position 107 on the incidence screen 122 spaced away from the camera 105.

[0061 ] According to the embodiment shown, the incidence screen 122 is translucent and which may be orientated vertically across a front surface 124 of the housing 1 19. As such, Figure 3 shows an interior view of the housing 1 19 from the perspective view of the camera 105 wherein the light beam 103 is visible through the translucent screen 122. The translucent screen 122 is not entirely transparent so that the light beam 103 striking the screen 122 is diffused to a visible bright spot able to be detected by the camera 105.

[0062] In embodiments, the light emitter 101 transmits a beam of light 103 within the visible spectrum, such as a red beam of light. As alluded to above, the system 100 may schedule the transmission of the beam of light 103 during the early hours of the morning so as to not to cause visible nuisance and to enhance the visibility of the incidence position 103 when it is dark. [0063] In embodiments, the camera 105 may comprise a light filter effectively acting as a light frequency range bandpass filter for the frequency of light of the light beam 103.

[0064] In alternative embodiments, the light emitter 101 and the camera 105 may transmit and detect a beam of light 103 outside the visible spectrum, such as infrared. [0065] Figure 20 illustrates an exemplary measurement process 125 implemented by the optical receiver module 104.

[0066] At step 126, the optical receiver module 104 may wake from the sleep state according to the measurement schedule.

[0067] At step 127, the optical interpretation controller 106 captures pixels at a Y coordinate position of the beam of light 103 on the screen 122 within the field of view of the camera 105. For example, the camera 105 may have an optical resolution of the incidence screen 122 of 10 pixels across and 300 pixels high example.

[0068] At step 128, the controller 106 may determine the colour or intensity at the position. The colour intensity may be measured against a threshold which may be set by the settings 1 15 or dynamically determined by the controller 106 to account for fluctuations in ambient light levels.

[0069] If a threshold is exceeded at step 129, the controller 106 may record the Y coordinate of the incidence position 107 at step 130.

[0070] Over a long time period, the Y pixel coordinate may drift. During initial installation, the controller 106 may record the initial Y pixel coordinate as the reference position and then calculate positive or negative offset relative thereto.

[0071 ] For example, during initial configuration, the controller 106 may detect the incidence position 107 at Y pixel coordinate 150 which may drift to Y pixel coordinate 173 over a six-month time period.

[0072] The system 100 may resolve the pixels into an actual offset according to the pixel resolution and the length of the screen 104. For example, for a 10 cm screen resolved into 300 pixels, a drift of 23 pixels would therefore represent a movement of

7.6 mm. [0073] Figures 5 and 6 show the light emitter 101 in accordance with two embodiments wherein the light emitter 101 may similarly comprise a circuit board 120 and a battery power supply 121 configured for the long duration operation of the light emitter 101.

[0074] The embodiment of Figure 5 is an omnidirectional light emitter 101 wherein the laser transmitter 102 transmits the beam of light 103 onto a conical reflector 131 to transmit a plane of light 103 through 360° with respect to the light emitter 101 .

[0075] The laser transmitter 102 and the conical reflector 131 may be configured to self-level.

[0076] Figure 6 shows an embodiment wherein the laser transmitter 102 of the light emitter 101 is configured to emit a directed beam of light 103. In embodiment shown in Figure 6, the light emitter 101 may comprise a first laser transmitter 102 configured to emit a visible beam of light 103A (such as a red laser beam) and a further invisible beam of light 103B (such as infrared laser beam).

[0077] The visible beam of light 103 may be used for aiming during system 100 installation whereas the invisible beam of light 103B may be used for subsequent measurements.

[0078] Figure 7 shows an embodiment wherein a module 101 , 104 may be mounted from the ceiling 135 using a right-angled bracket 133. Alternatively, the module 101 , 104 may be mounted to the floor 134 using the bracket 133.

[0079] Figure 8 shows an embodiment wherein the modules 101 , 104 may be wall mounted.

[0080] Figures 9 - 1 1 shows an embodiment wherein the modules 101 , 104 may be installed using a combination of wall mounting and ceiling or floor mounting brackets. [0081 ] Figure 12 shows an embodiment wherein a marked reference marker 136 is attached to a wall which defines the target surface and wherein the beam of light 103 is directed thereto by the light emitter 101. The marked reference marker 136 comprises a reference mark which is shown as a reference line 137.

[0082] The marked reference marker 136 may be initially installed so that the beam of light 103 coincides with a central reference line 137. Over time, the incidence position 107 of the beam of light 103 may drift with respect to the reference line 137. [0083] Using a mobile phone device, the user may take a photo of the marked reference marker 136 using the camera of the mobile phone device. Bespoke software application executing thereon may optically analyse the image data to optically determine the offset of the incidence position 107 from the reference line 137, such as by making optical reference to the associated gridlines. Alternatively, the mobile phone device may upload image data to the server 1 10 for image processing.

[0084] In alternative embodiments, the reference mark may be an icon or other computer vision recognisable object on the target surface which allows for automatic optical recognition to thereby determine the offset between the beam of light 103 incidence and the object using computer vision analysis.

[0085] Simultaneously, the software application may read an ID of the marked reference marker 136 using optical character recognition. As such, the software application may determine an offset incidence position and transmit the reading to the server 1 10 along with the ID of the marked reference marker 136. Alternatively, the ID may be encoded in computer readable media, such as a QR code.

[0086] Figure 14 shows an exemplary installation comprising a floor mounted light emitter 101 , an internal wall 140 floor mounted receiver module 104A and an opposite wall 141 floor mounted receiver module 104B.

[0087] As is illustrated in Figure 14, slab heave displacement 139 may be measured by the opposite wall 141 floor mounted receiver module 104B. As such, the system 100 is able to determine that the floor/slab has remained stationary at the internal wall 140 although has moved vertically at the opposite wall 141 .

[0088] Figures 13 and 15 illustrate using line-of-sight pairs of light emitters 101 and target surfaces and non-line-of-sight pairs 142 of light emitters 101 and target surfaces to accurately measure structural displacement across a plurality of rooms 152 in a multi-room building. As can be appreciated from this arrangement, line-of- sight targeting is not possible across the rooms 152. In the embodiment shown, the target surfaces of the receiver modules 104 are used. However, the target surface of the aforedescribed marked reference markers 136 may be alternatively employed. [0089] As is shown in Figure 15, a building may comprise two rooms 152 separated in between by a dividing wall 143 and bounded by outer walls 141 . The system 100 may be programmed with tiers of line-of-sight light emitters 101 and target surfaces in each room. For example, Figure 13 shows a three-room configuration having a main tier 1 and secondary tiers 2, each having respective light emitters 101 and receivers 104 in line-of-sight with each other. Figure 13 also shows wherein a light emitter 101 is configured to emit a plane of light towards more than one target surface/receiver 104 in each room.

[0090] Light emitter 101 A may be configured as representing the primary datum point and wherein relative displacement in the rooms is calculated relative to the primary data point.

[0091 ] The system 100 may also be programmed with non-line-of-sight pairs of light emitters 101 and target surfaces attached to opposite sides of the dividing structural wall 143 between the adjoining rooms 152.

[0092] For example, with reference to Figure 15, light emitter 101 B and receiver module 104C may be programmed as the non-line-of-sight pair 142 being located either side of the dividing wall 143 so as to move synchronously with the dividing wall 143.

[0093] The system 100 is configured to measure target surface light incident offset in each room 152. As such, the system 100 is also programmed with the line-of-sight pairs of emitters 101 and receiver modules 104 in each room 152. For example, with reference to Figure 15, the system 100 may be programmed that emitter 101 B and receiver module 104D are a first line-of-sight pair in a first room 152A and that emitter 101 A and receiver module 104C are a second line-of-sight and a second room 152B. [0094] As such the system 100 can automatically detect displacement of the first outer wall 141 A of the first room 152A when detecting target surface light incident offset in the first room 152A only. The system 100 can also automatically detect displacement of the second outer wall 141 B of the second room 152B when detecting target surface light incident offset in the second room 152B only. The system 100 can also automatically detect displacement of the dividing wall 143 when detecting target surface light incident offset in both of the adjoining rooms 152A and 152B in the same vertical direction.

[0095] For example, should there be slab heave displacement 139 at the dividing wall 143 as is illustrated in Figure 15, the system 100 may detect the slab heave displacement 139 at the dividing wall 143 as opposed at the opposite walls 141 by comparing the offset measured at the receiver module 104C at the dividing wall 143 to the offset measured at the receiver module 104D at the opposite wall 141 A. If the displacement is substantially the same magnitude and in the same direction, the system 100 and thereby detect displacement of the dividing wall 143.

[0096] As such, even though the receiver module 104D at the opposite wall 141 registers an offset in the incidence position 107, the system 100 is able to determine that the opposite wall 141 has not moved because the light emitter 101 B and the receiver module 104C are programmed as belonging to the same non-line-of-sight reference pair 142 and a corresponding displacement was measured by the receiver module 104C.

[0097] In scenarios where there is movement at more than one wall, the measured displacements would not of the same magnitude. For example, a greater displacement may be measured at the receiver module 104D as compared to receiver module 104C. As such, the system 100 may deduce that both the first outer wall 141 A and the dividing wall 143 moving. In this scenario, to differentiate the vertical movement between the first outer wall 141 A and the dividing wall 143 and assuming that the displacement measured at both receivers 104D and 104C is in the same direction, the displacement measured at the receiver 104C would represent the vertical displacement of the dividing wall 143 whereas the difference between the displacement measured by the receiver 104D at the outer wall 141 A and the receiver 104C at the dividing wall 143 would represent the displacement of the outer wall 141 A.

[0098] Figure 20 shows an exemplary displacement trendlines for the arrangement given in Figure 15 which comprises a first room 152B and a second room 152B separated by a dividing wall 143. The first room 152A is bounded by a first outer wall 141 A and the second room 152B is bounded by a second outer wall 141 B.

[0099] In the first room 152A is installed a single emitter 101 B light of the embodiment given in Figure 5 which emits a plane of light 103 onto a pair of receiver modules 104D1 and 104D2.

[0100] Trend 153A represents displacement between the emitter 101 B and the first receiver module 104D1 and trend 153B represents displacement between the emitter 101 and the second receiver module 104D2.

[0101 ] In the second room 152B is installed a single emitter 101 A on the second outer wall 141 B which directs a beam of light 103 onto a single receiver module 104C on the dividing wall 143.

[0102] Trend 153C represents displacement between the emitter 101 A and the single receiver module 104C.

[0103] The system 100 is programmed that the transmitter 101 B and the receiver 104C are a non-line-of-sight pair, and that the transmitters 101 and respective receivers 104 in each room 152 are line-of-sight pairs.

[0104] The trends 153A and 153B show similar displacement between the emitter 101 B and the pair of receivers 104D1 and 104D2 indicative that either the first outer wall 141 A or the dividing wall 143 is shifting vertically. However, the trend 153C shows negligible displacement between the transmitter 101 A and the receiver 104C in the second room 152B. As such, the system 100 is able to detect movement of the first outer wall 141 A only according to the respective programming of the line-of-sight pairs and the non-line-of-sight pairs. In this example, the system 100 is able to deduce that the first outer wall 141 A has shifted by 5 mm whereas the dividing wall 143 and the second outer wall 141 B have remained static. Furthermore, the system 100 may be programmed that it is more likely that a single outer wall 141 A would displace as compared to the more unlikely scenario of both the dividing wall 143 and the second outer wall 141 B synchronously. [0105] Figure 16 shows an exemplary graphical user interface 144 which may be rendered by the server 110. The interface 144 shows a floorplan and a plurality of floor level movement indicators 145 superimposed thereon.

[0106] Each indicator 145 may display a measured floor level movement (either positive to indicate floor heave or negative to indicate floor subsidence) in millimetres and which may be coloured according to a categorisation thereof. For example, movement of 5 mm or less is shown in green, movement of 10 mm or less is shown orange and movement of more than 10 mm is shown in red.

[0107] Figure 15 shows a long-term trend 146 which may be generated by the server 110.

[0108] In embodiments, the system 100 comprises a plurality of soil moisture measurement sensors (not shown) and rainfall sensor.

[0109] As such, the long-term trend 146 may have a rainfall measurement trend 147, a plurality of soil moisture content trends 148 and a floor level movement trend 149.

[01 10] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

Claims

1 . A structural displacement monitoring system for a building comprising multiple rooms, the system comprising light emitters configured to emit a focused beams of light onto respective target surfaces wherein the system is configured to optically ascertain target surface light incident offset to measure relative displacement, wherein the system is programmed that: light emitter and respective target surface pairs in respective first and second adjoining rooms are line-of-sight pairs; a light emitter and a respective target surface pair attached to opposite sides of a dividing structural element between the adjoining rooms are a non-line-f- sight pair, wherein, in accordance with the programming, the controller is configured to measure target surface light incident offset between line-of-sight pairs in each room to: detect displacement of a structural element of the first room when measuring target surface light incident offset between a line-of- sight pair in the first room only; detect displacement of a structural element of the second room when measuring target surface light incident offset between a line-of- sight pair in the second room only; and detect displacement of the dividing structural element when measuring target surface light incident offset between line-of-sight pairs in both adjoining rooms in the same vertical direction.

2. The system as claimed in claim 1 , wherein, in accordance with the programming, the system is further configured to detect movement in both the structural element of the first room and the dividing wall when detecting that the displacement measured between the line-of-sight pair in the first room is not of the same magnitude at the displacement measured between the line-of-sight pair in the second room.

3. The system as claimed in claim 1 , wherein the system comprises an optical receiver module installed within line-of-sight of a light emitter, the optical receiver module comprising a camera and a controller operably coupled thereto, wherein the controller is configured to periodically measure an incidence position of a beam of light on a target surface of the optical receiver module over a long time period.

4. The system as claimed in claim 1 , wherein the system comprises a reference marker attached to at least one of the structural elements and wherein the system is configured to receive a photo taken of the reference marker using a mobile phone device and to optically analyse the image to determine light incident offset.

5. The system as claimed in claim 4, wherein the reference marker comprises a reference mark and wherein the system is configured to optically determine an offset between a light beam incidence position and the reference mark.

6. The system as claimed in claim 4, wherein the reference marker comprises an ID and wherein the system is configured to read the ID using optical character recognition.

7. The system as claimed in claim 4, wherein the reference marker comprises computer readable media optically encoding an ID and wherein the system is configured to decode the ID from the computer readable media.

8. The system as claimed in claim 1 , wherein a light emitter comprises a controller which controls the light emitter to periodically emit a beam of light.

9. The system as claimed in claim 3, wherein a light emitter comprises a controller which controls the light emitter to periodically emit a beam of light wherein a controller of an optical receiver module is configured for synchronising measurement with transmissions from the light emitter.

10. The system as claimed in claim 9, wherein the controllers are configured with respective transmission and measurement schedules.

1 1. The system as claimed in claim 10, wherein the optical receiver module defaults to a sleep state and periodically wakes from the sleep state according to the transmission and measurement schedule.

12. The system as claimed in claim 10, wherein the optical receiver module comprises a data interface for sending and receiving data across a wide area network and wherein the module receives the measurement schedule from a server across the wide area network.

13. The system as claimed in claim 3, wherein the optical receiver module comprises a data interface for sending and receiving data across a wide area network and wherein the optical receiver module is configured to transmit measurement data to a server across the wide area network.

14. The system as claimed in claim 3, wherein the camera is spaced away from an incidence screen defining a target surface and wherein the controller is configured for measuring an incidence position according to a relative visible offset of the beam of light of the incidence screen.

15. The system as claimed in claim 14, wherein the optical receiver module comprises a housing and wherein the incidence screen is translucent and vertically orientated across a front surface of the housing and wherein the camera is spaced away from the screen within the housing.

16. The system as claimed in claim 4, wherein the controller of the optical receiver module is configured to threshold at least one of colour and intensity to determine the incidence position.

17. The system as claimed in claim 16, wherein the controller of the optical receiver is configured to dynamically adjust the threshold according to ambient light levels.

18. The system as claimed in claim 1 , wherein the beams of light are within the visible spectrum.

19. The system as claimed in claim 18, wherein the system is configured to transmit beams of light only when it is dark.

20. The system as claimed in claim 1 , wherein the beams of light are not in the visible spectrum of light.

21 . The system as claimed in claim 20, wherein the beams of light are ultraviolet.

22. The system as claimed in claim 3, wherein an optical filter interfaces the camera and which acts as a light frequency bandpass filter according to a frequency of the beam of light.

23. The system as claimed in claim 1 , wherein a line-of-sight pair comprises a light emitter which transmits a light towards more than one target surface.

24. The system as claimed in claim 23, wherein the light emitter has a conical reflector to transmit the plane of light.

25. The system as claimed in claim 24, wherein the conical reflector is configured to self-level.

26. The system as claimed in claim 1 , wherein a light emitter comprises a first laser transmitter configured to emit a visible beam of light and a further invisible beam of light.

27. The system as claimed in claim 1 , wherein a module is mounted from a ceiling.

28. The system as claimed in claim 1 , wherein a module is mounted on a floor.

29. The system as claimed in claim 1 , wherein a module is mounted on a wall.

30. The system as claimed in claim 1 , wherein the system is configured to generate a graphical user interface showing a floorplan and a plurality of floor level movement indicators superimposed thereon.

31 . The system as claimed in claim 30, wherein each indicator displays a measured floor level movement.

32. The system as claimed in claim 30, wherein each indicator is coloured according to a categorisation of the measured floor level movement.

33. The system as claimed in claim 1 , wherein the system further comprises soil moisture sensors and wherein the system is further configured for generating a longterm trend comprising soil moisture content trends with reference to a floor level movement trend.

34. The system as claimed in claim 33, wherein the system further comprises a rainfall sensor and wherein the long-term trend further comprises a long-term rainfall trend.