AU2017203165B2

AU2017203165B2 - Method and System for Collection of Photographic Data

Info

Publication number: AU2017203165B2
Application number: AU2017203165A
Authority: AU
Inventors: Thomas Caska; Matthew Dunn
Original assignee: Aerologix Group Pty Ltd
Current assignee: Aerologix Group Pty Ltd
Priority date: 2016-11-09
Filing date: 2017-05-12
Publication date: 2022-08-18
Anticipated expiration: 2037-05-12
Also published as: AU2017203165A1; AU2020104135A4; AU2022271430A1; AU2020104135B4

Abstract

In an aspect, there is provided a method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device, the method including the steps of: flying the unmanned aerial vehicle in a first flight path in one or more first orbits about the vertical structure and capturing a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and flying the unmanned aerial vehicle in a second flight path in one or more second orbits about the vertical structure, the one or more second orbits being at least partially inward of the one or more first orbits toward the vertical structure, and capturing a plurality of overlapping images of the vertical structure with the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle. Additional methods and a related system are also disclosed. 1/9 10 14V 18 22 1 6 20 12 Wireless Communication 24 26 FIGURE 1

Description

1/9 10

14V

18 22

12 16 20

Wireless Communication

24

26

FIGURE 1

Method and System for Collection of Photographic Data

Related Applications

[001] This application claims priority from Australian provisional patent application no. 2016904578 filed on 9 November 2016, the contents of which are incorporated by reference.

Technical Field

[002] The invention relates to a method and system for collection of photographic data, more specifically, the invention relates to a method and system for collection of photographic data of a vertical structure, such as a tower, suitable to form a digital model of the vertical structure.

Background

[003] It is desirable to create digital models of vertical structures, such as transmission towers, for digital asset management. Accordingly, methods have been developed to attempt to capture digital images of such vertical structures using unmanned areal vehicles (UAVs), commonly known as drones, and then reconstructing these images, using advanced photogrammetry software such as Pix4DTM

[004] Vertical structures, especially thin tall towers, are difficult to model based on photogrammetry data because the members are thin, reflective and the external members may obstruct the internal members.

[005] A method used to capture these images includes flying the UAV in close orbits around the structure at varying heights such as via a spiral. A camera carried by the UAV may be angled at a 45-degree angle pointing toward the ground and the images may be captured so as to have overlap between the images that may be, typically, at least 85% frontal and side overlap. The images are then processed, such as by use of Pix4DT, to provide a digital model of the vertical structure.

[006] A problem with this method is that the captured images lack sufficient information to construct the vertical tower at a resolution or accuracy that is appropriate for digital asset management, namely engineering, purposes whereby the accuracy of, for example, the length of members of the structure are required to be known to a high accuracy.

[007] The invention disclosed herein seeks to overcome one or more of the above identified problems or at least provide a useful alternative.

Summary

[008] In accordance with a first broad aspect there is provided, a method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device for input to a model, the method including the steps of: flying the unmanned aerial vehicle in a first flight path in one or more first orbits about the vertical structure and capturing a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and flying the unmanned aerial vehicle in a second flight path in one or more second orbits about the vertical structure, the one or more second orbits being at least partially inward of the one or more first orbits toward the vertical structure, and capturing a plurality of overlapping images of the vertical structure with the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle.

[009] In an aspect, the first and second flight paths respectively include pluralities of the first and second orbits made vertically along the vertical structure.

[0010] In another aspect, the first and second flight paths respectively include pluralities of the first and second orbits made at pre-determined discrete vertical increments along the vertical structure, and wherein the plurality of overlapping images are captured at each of the at pre-determined discrete vertical increments.

[0011] In yet another aspect, the discrete vertical increments of the each of the first and second orbits are substantially the same so as to provide pluralities of images captured outwardly and inwardly relative to one other at substantially the same vertical height.

[0012] In yet another aspect, the first and second flight paths respectively include pluralities of the first and second orbits made at pre-determined continuous vertical increments along the vertical structure so as to form first and second spiral orbits.

[0013] In yet another aspect, the first orbit is initiated from a location toward a top of the vertical structure and the first angle is at least initially set to capture the entire tower frame and the ground surface.

[0014] In yet another aspect, the first angle is in the range of about 45 to 60 degrees downward relative to the horizontal.

[0015] In yet another aspect, the first angle is varied as the first flight path moves along the vertical structure.

[0016] In yet another aspect, the first orbit has a radius of between about 2/3 and 1 1/3 of the height of the vertical structure.

[0017] In yet another aspect, the second angle is in the range of about 0 to 10 degrees upward or downward from the horizontal.

[0018] In yet another aspect, the second angle is varied as the second flight path moves along the vertical structure.

[0019] In yet another aspect, the second orbit has a radius of between about 1/3 and 2/3 of the height of the vertical structure.

[0020] In yet another aspect, the first orbit is an outer orbit and the second orbit is an inner orbit, the inner and outer orbits being substantially non-overlapping.

[0021] In yet another aspect, the first and second orbits are circular.

[0022] In yet another aspect, one or both of thefirst and second orbits are elliptical.

[0023] In yet another aspect, the method includes the step of: flying the unmanned aerial vehicle above the vertical structure so as to determine a vertical axis about which the first and second orbits are flown.

[0024] In yet another aspect, the method includes the steps of: determining at least two offset axes that are each laterally offset from a vertical axis of the tower structure and from one another; and wherein the first and second orbits are flown about respective ones of the at least two offset axes.

[0025] In yet another aspect, the method includes the steps of: determining a plurality of offset axes that are each laterally offset from a vertical axis of the tower structure and from one another; and wherein the first and second orbits are provided in the form of a plurality of orbits that are flown about respective ones of the plurality of offset axes.

[0026] In accordance with a second broad aspect there is provided, a system including an unmanned aerial vehicle and an image-capturing device configured to perform a method as defined above and herein.

[0027] In accordance with a third broad aspect there is provided, digital model of a vertical structure formed substantially with images captured by a method as defined above and herein.

[0028] In accordance with a fourth broad aspect there is provided, a collection of digital images including images captured by a method as defined above and herein.

[0029] In accordance with a fifth broad aspect there is provided, a system including unmanned aerial vehicle and an image capturing device for collecting photographic data of a vertical structure for input to a model, the system being configurable to: fly the unmanned aerial vehicle in a first flight path in one or more first orbits about the vertical structure and capturing a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and fly the unmanned aerial vehicle in a second flight path in one or more second orbits about the vertical structure, the one or more second orbits being at least partially inward of the one or more first orbits toward the vertical structure, and capturing a plurality of overlapping images of the vertical structure with the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle.

[0030] In accordance with a sixth broad aspect there is provided, a method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device for input to a model, the method including the steps of: flying the unmanned aerial vehicle in a plurality of overlapping orbits, when viewed in plan form, about the vertical structure, each of the plurality of overlapping orbits being about a respective plurality of offset axes that are each offset from a vertical axis of the vertical structure and from one another, and capturing, in each of the plurality of overlapping orbits, a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at an angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure.

[0031] In accordance with a seventh broad aspect there is provided, a system including unmanned aerial vehicle and an image capturing device for collecting photographic data of a vertical structure for input to a model, the system being configurable to: fly the unmanned aerial vehicle in a plurality of overlapping orbits, when viewed in plan form, about the vertical structure, each of the plurality of overlapping orbits being about a respective plurality of offset axes that are each offset from a vertical axis of the vertical structure and from one another, and capturing, in each of the plurality of overlapping orbits, a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at an angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure.

[0032] In accordance with a eighth broad aspect there is provided, a method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device for input to a model, the method including the steps of: capturing one or more first images using the image capturing device of the unmanned aerial vehicle at a first distance from the vertical structure with the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and capturing one or more second images using the image capturing device of the unmanned aerial vehicle at a second distance from the vertical structure, the second distance being relatively closer to the tower and the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle.

[0033] In accordance with a ninth broad aspect there is provided, a method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device for input to a model, the method including the steps of: capturing at least one outer image using the image capturing device at a first distance from the vertical structure, the image capturing device being at a first angle so as to capture at a feature of at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and capturing one or more inner images using the image capturing device at a second distance from the vertical structure the second distance being relatively closer to the tower and the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle and being such that a least one of the one or more inner images provides further detail of the feature of the vertical structure also captured in the at least one outer image.

[0034] In accordance with a tenth broad aspect there is provided, a method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device for input to a model, the method including the steps of: flying the unmanned aerial vehicle in a first flight path and capturing at least one outer image using the image capturing device at a first distance from the vertical structure, the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and flying the unmanned aerial vehicle in a second flight path and capturing one or more inner images using the image capturing device at a second distance from the vertical structure the second distance being relatively closer to the tower and the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle and being such that a least one of the one or more inner images provides further detail of a feature of the vertical structure also captured in the at least one outer image.

Brief Description of the Figures

[0035] The invention is described, by way of non-limiting example only, by reference to the accompanying figures, in which;

[0036] Figure 1 is a schematic diagram illustrating a system for collecting photographic data of a vertical structure;

[0037] Figure 2 is a side view illustrating the UAV at an initial vertical height above the tower to determine a vertical orbit axis;

[0038] Figures 3 and 4 are are perspective diagrams illustrating the system, namely, the UAV being flown in inner and outer orbits, respectively about the vertical structure;

[0039] Figure 5 is a diagrammatic perspective view illustrating the UAV at inner and outer locations with respective overlapping inner and outer images;

[0040] Figure 6a to 6d illustrate a diagrammatic sequence respectively showing capturing inner and outer images via inner and outer orbits, associating a feature of the outer image with more detailed features of the inner images, and an example digital model output reconstructed from the inner and outer images.

[0041] Figure 7 is a flow diagram illustrating a first method for collecting photographic data of a vertical structure;

[0042] Figure 8 is a flow diagram illustrating a second method for collecting photographic data of a vertical structure; and

[0043] Figure 9 is a plan form diagram illustrating orbits of the first and second methods about the vertical structure.

Detailed Description

[0044] Referring to Figures 1 to 8, there is shown a system 10 and method 110 for collecting photographic data, more specifically images of a vertical structure 12 using an unmanned aerial vehicle (UAV) 14 carrying an image-capturing device 16 for providing input to a digital model. The vertical structure 12 may be any form of vertical structure, including, but not limited to, telecommunication towers and similar slender space-frame or monopole structures. The UAV 14 may be a drone 18 such as those available from DJITM. Of course, other suitable drones or UAVs may be used. The drone 18 may be piloted or autonomous following a pre-defined flight path.

[0045] The image-capturing device 16 may be a high-resolution digital camera 20 such as those having a 20-megapixel resolution or better. The camera 18 settings may be inputted and modified as need be for the required resolution, clarity and image properties. The camera 18 is carried by a controllable gimbal 22 that allows the controlled angling and rotation of the camera 20. The drone 18, camera 20 and gimbal 22 may be controlled by a controller 24 such as a handheld remote controller fitted with a screen 26 or the like. Such drones 18, cameras 20, gimbals 22 and controllers 24 are commercially available and are not described in any further detail herein. It is noted that the controller 24 may preferably operate software, such as in this example the DJITm Go app, that includes features such as grid lines and control points to assist with the flight paths and performing methods disclosed herein. The DJIIm Go app is commercially available and is not described herein in any further detail. Other suitable programmable autonomous flight control software is also available. It is envisaged that in some examples the drones 18 may be fully autonomous and operated from a remote base station or the like.

[0046] Each captured image may be stored in memory of the camera or transmitted to a base station, or other storage medium. Each captured image is stored with associated meta-data that includes image identity, location, time and accuracy data. The image identity may be a number or sequence code to assist to relate the captures images to other associated images during processing, such as a sequence or orbit number or type. The location information may include spatial information including real-time GPS coordinates to determine a point in space (i.e. latitude, horizontal and vertical) and a barometer may be used to provide additional vertical (i.e altitude) data. The estimated accuracy of the location data may also be stored with the meta-data.

Method Overview

[0047] The methods disclosed herein relate to collecting photographic data of the vertical structure 12 using the unmanned aerial vehicle 14 carrying the image capturing device 16 for input to a model such as a computer photogrammetry model for generating a digital model of the vertical structure 12. The methods disclosed herein are particularly adapted for use with space frame vertical structures that include multiple beams that at times obstruct one another from view of the camera. The towers often also carry complex structures and attachments such as brackets and antennas.

[0048] The methods generally include capturing overlapping image data from a plurality of discrete outer and inner positions relative to the tower and structures or items of interest of the tower. The outer positions are used to capture outer images that generally include a wider portion of the tower and ground reference points. The inner positions are utilised to capture more detailed images of the tower that may also be captured at a different angle to the images of the outer positions. There are pluralities of inner images that are captured for each of the outer images.

[0049] Importantly, the optical settings, namely the zoom, for the image capturing device 16 are preferably maintain constant between the inner and outer positions. For example, a 1x optical zoom may be set. This ensures that the perspective and, importantly proportions, of the vertical structure 12 remain consistent between the captured inner and outer imaged so that details of the structure can be captures. This is particularly important for space frame structures that include beams that are often one behind the other and the relative proportions of each beam are required to be maintained. Accordingly, the methods disclosed herein generally include physically moving the image capturing device 16 inwardly and outwardly of the tower using consistent and fixed zoom so as to provide depth of field of view thereby allowing imaging and extraction of complex parts and structure of the tower on the surface and within the tower.

[0050] The methods disclosed herein are particularly suitable for telecommunication towers that are usually live and emitting a relatively high EMF (Electromagnetic Field). Accordingly, in this use scenario, during operations the UAV 14 is operated so as to be continuously moving, preferably, at a continuous orbital velocity in the range of about 1 m/s to 3 m/s. It has been found that the continuous orbital velocity assists to reduce EMF interference. A speed of about 2 m/s has been found to be suitable and appropriate for utilised camera shutter speeds.

Example Method 1

[0051] Referring to Figure 2 to 8, the method110 generally includes three main steps being, a step 120 determining a vertical axis "V" of the vertical structure 12, and then flying first and second orbits about the vertical axis as detailed in steps 130 and 140 below and as shown in Figures 2 and 7. It is noted that step 120, a vertical axis "V" of the vertical structure 12, may not be essential in all examples of the method 110 as the vertical axis "V" may be predetermined.

Determining the Vertical Axis "V"

[0052] At step 120, and as shown in Figure 2, the vertical axis "V" of the vertical structure 12 is determined by flying the UAV above the vertical structure 12. The vertical axis "V" is used as a centre of the inner and outer orbits as outlined below, and may need to be re-determined or checked for each orbit.

[0053] The method 110 may at step 120, further including one or more of the steps as outlined below, including, initially, flying the UAV vertically from the takeoff location to an altitude "H 1" clearly above the tower structure 12 at "P 1" as shown in Figure 2. The structure 12 may be, in some examples, about 30 meters (100 feet in height). The UAV may be flown towards the structure 12. The height of the top of the structure may be noted or recorded and the UAV is then flown to a height that is above, typically about 50% higher (i.e. 15 metres in this example) than the highest point of the structure 12. When positioned over the centre of the tower structure 12, the on-board camera 20 may be tilted 90 degrees downwards so that it is looking directly below without any angles (nadir). The approximate North, East, South and West position of the structure 12 may then be determined and recorded for navigation and flight planning purposes.

[0054] Next, the UAV may be positioned directly over and centred over the tower structure 12. The gridlines in the DJI Go App may be used to help with this central positioning. It is important that the centred location is accurately centred as the UAV will fly a circular flight pattern around the structure 12. It is important that the vertical axis centre point is not significantly off-centre as this may result in an unintentional elliptical orbit relative to the tower structure 12. In the worst case, the orbit path may cross through the tower structure at lower heights. The centred location may be recorded using Point of Interest (POI) function on the DJI Go app.

Outer Position or Orbits

[0055] The method 110, then includes step 130 in which the unmanned aerial vehicle 14 is flown in a first flight path as shown in Figure 3 in the form of one or more first orbits (01.1, 01.2... 01.,) that are preferably outer positions or orbits, about the substantially vertical axis "V" of the vertical structure 12 and capturing a plurality of overlapping outer images (I1, 12,...I) of the vertical structure 12 with the image capturing device 16. The image capturing device 16 being oriented at a first angle "A 1" so as to capture at least some of the vertical structure 12 and at least some of a ground surface "G" proximate the vertical structure 12.

[0056] The method 110, at step 130, may in more detail include one or more the following steps. Setting outer orbit radius to about 1/3 to 1 1/3 of the vertical structure 12 height. In this example, in which the vertical structure 12 is about 30 metres (100ft) high, the outer orbit radius should preferably be between 20m and 40m (65 feet to 135 feet) depending on obstacles, wires and any other hazards identified.

[0057] The first angle "Al", of the camera 20, may be between 45-60 degrees relative to the horizontal or at an angle which captures the entire frame of the structure 12 in the picture for at least the initial or highest outer orbit. The orbit velocity may be set that each orbit is 2 minutes in duration or about 2 m/s. However, the orbit velocity may have any suitable value to provide a sufficient number of images and the desired overlap. On the controller 24, the operator may Press Start and Click the camera shutter button to take one photo per second. The UAV may need to be centred using the yaw control if the centre of the tower drifts out of the central view of the camera 20. Ensure that at least 120 photos are taken for each of the outer orbits or such that about 85% or greater overlap is provided.

[0058] A plurality the outer orbits, as defined above, may be flown at intervals vertically along the vertical structure 12. The orbits (01.1, 01.2... 01.,) each include a plurality of laterally overlapping images (I,1.2,.. that also vertically overlap with images of adjacent orbits. In this example, the discrete intervals may be about 1/8 to % of the vertical height of the vertical structure 12. In this example, the discrete intervals may be about 5 metres (or about 20 feet) and the first angle, being the tilt of the camera 18, may be reduced by 2-3 degrees for each lower orbit. Depending on the vertical height of the structure 12 and the required resolution, in the order of about at least 5 to 10 of the outer orbit may be flown.

Inner Position or Orbits

[0059] The method 110, then includes step 140, in which the unmanned aerial vehicle 14 is flown in a second flight as shown in Figure 4 in the form of one or more second orbits (02.2, 02.2... 02.,), that are preferably inner positions or orbits, about the substantially vertical axis of the vertical structure 12. The one or more second orbits being substantially inward of the one or more first orbits toward the vertical structure 12. A plurality of overlapping images (12, 12.2,...12.) of the vertical structure 12 are again captured using the image capturing device 16 with the image capturing device 16 being at a second angle "A2 ", the second angle being relatively oriented toward the vertical structure 12 in comparison to the first angle.

[0060] The method 110, may at step 140, further include one or more of the steps as outlined below, including initially if required, performing step 120 to re-determine the vertical axis "V" of the vertical structure 12. The inner orbit radius may be set to be between about 1/3 and 2/3 the height of the vertical structure 12. In this example, the inner orbit radius may be between about 1Om to 20m (30 feet to 65 feet) depending on obstacles, wires, etc. The camera 18 may be oriented to focus on the vertical structure 12 having a tilt such that the second angle is about 10 degrees relative to the horizontal. The orbit velocity may be set to about 2 minutes in duration or about 2 m/s, and the operator may Press Start and Click the camera shutter button to take one photo per second via the controller 24. The operator may then centre the UAV using the yaw control of the controller if the centre of the structure 12 drifts out of the central view of the camera. Ensure that at least 120 photos are taken for each orbit so as to have at least an 85% overlap.

[0061] A plurality the inner orbits, as defined above, may be flown at intervals vertically along the vertical structure 12, as shown in Figures 2 and 11. In this example, the discrete intervals may be about 1/8 to % of the vertical height of the vertical structure 12. In this example, the discrete intervals may be about 5 metres (or about 20 feet) and the second angle, being the tilt of the camera 18, may be raised or reduced by 2-3 degrees for each lower orbit. Depending on the vertical height of the structure 12 and the required resolution, in the order of about at least 5 to 10 of the inner orbits may be flown. It is noted the inner and outer orbits may be flown in reverse order with the inner orbits flown first. Alternatively, the flight path may include further orbits more between the inner and outer orbits for each vertical height.

[0062] Preferably, the vertical intervals of the inner and outer orbits are each substantially aligned with one another so that there are pairs of inner and outer orbits for each discrete vertical height. However, this is not always the case and, of course, in some examples the vertical height may be continuous such that spiral patterns are flown about the vertical structure 12 and substantially similar method as outlined above would apply with such spiral inner and outer orbits. It is noted in this example the orbits are generally circular. However, in some examples the orbits may be elliptical, non-circular, hexagonal, free-form about the tower or any other suitable shape. It is also noted that whilst inner and outer "orbits" have been described, in some examples, there may be other intermediate orbits or positions and the methods discloses herein are not restricted to defined inner and outer orbit, as such.

Results & Processing

[0063] The method 110 and system 10 provide a plurality or set of overlapping images from each of the inner and outer orbits along the vertical height of the vertical structure 10 that have provided sufficient resolution to be processed by advanced TM photogrammetry software, such as that available from Bentley Systems , to provide digital models of tower structures have resolutions in the order of 1mm or better on structural members or beams of the structure 12.

[0064] In more detail, referring to Figure 5 each inner and outer orbit for each vertical height will have acquired data as follows as a function of height: • Outer (01.1, (I1, I12..1») 0 .,(1 12..1»)etc;

• Inner (02.1, (11, 11.2,..11 ), (02.2, (12, 12.2,...12.)) etc;

[0065] As shown in Figure 5, a plurality of the images 12 from the inner orbits 02

overlap with and may be associated with one or more of the images I1 of the outer orbits 01. Accordingly, the outer images provide broader context and the inner image provide detail and depth that may be associated with broader features of the outer images. Typically, a single outer image may be a few or tens of associated inner images that detail the same visual features such as parts or structures of the tower.

[0066] As shown in Figures 6a to 6d, for example, for each set of inner and outer orbits 02, 01 there are captured overlapping images I12...1) taken at differing distances from the tower. Again, the outer images provide overall context and location and the (I2...) provide the detailed images that can be process to match and build out the outer images with sufficient detail. These images are provided to the processing software in sets such as those shown in Figures 6b and 6c and processed by photogrammetry software to provide a digital model "Dm" of the tower as is shown in Figure 6d.

[0067] It is noted that some examples of the method may be captured with and processed with laser image data, referred to as LIDAR data or point cloud LIDAR data. The LIDAR data provides increase measurement accuracy on which the photogrammetry data may be overlaid.

Second Example - Overlapping Offset Orbits

[0068] Referring more specifically to Figures 4 and 5, the system 10 may also be utilised in a second example method 210 as best illustrated in Figures 4 and 5. Method 210 is similar to method 110 as outlined above however multiple overlapping orbits, as shown in Figure 4, are utilised rather than defined inner and outer orbits.

[0069] The method 210 generally includes two main steps being, a step 220 determining one or more offset orbit axes ("OL1", "OL2" etc, as shown in Figure 5) space apart from the vertical axis "V" of vertical structure 12, and then flying a series of overlapping orbits about each of the one or more offset orbit axes "0"as detailed in step 230 below. It is noted that in step 220, a vertical axis "V" of the vertical structure 12, may not be essential in all examples as the vertical axis "V" may be predetermined.

Determining the Vertical Axis "V"

[0070] At step 220, the vertical axis "V" of the vertical structure 12 is determined by flying the unmanned aerial vehicle above the vertical structure 12. Next, a series of offset orbit axes ("01", "02" etc) are determined at spaced apart locations relative the vertical axis "V". In this example, four orbit axes "OA" are determined that at 90 degrees from one another being North East, South East, South West and North West.

The lateral distances between each of the our orbit axes "0" and the vertical axis "V" is close enough so that the UAV in each orbit can pass around the vertical structure 12 with the orbit radius set to be between about 1/3 and 2/3 the height of the vertical structure 12. In this example, the orbit radius may be 10m and 20m (30 feet to 65 feet) depending on obstacles, wires, etc. The offset may be about 2 to 4 metres.

Plurality of Overlapping Orbits

[0071] A plurality of orbits may be flown that are reach centred on a different offset orbit axes ("OAl", "OA2" etc.) In this example, the series of orbits are flown that are each centred on one of the North East, South East, South West and North West orbit axes. The angle of the camera 20 may be about 15 downward from the horizontal or at an angle which captures the tower at an oblique angle but without the sky and with minimal horizon features in the background. Each of the series of orbits may have a orbit radius that may be set to be between about 1/3 and 2/3 the height of the vertical structure 12, in this example being about 10 to 20 metres. The plurality of orbits may overlap when viewed in plan form as shown in Figure 9, but may not actually intersect when viewed from a side view.

[0072] Each of the four series of orbits may be flown at intervals vertically along the vertical structure 12. In this example, the discrete intervals may be about 1/8 to % of the vertical height of the vertical structure 12. In this example, the discrete intervals may be about 5 metres (or about 20 feet) and the second angle, being the tilt of the camera 18, may be raised or reduced by 2-3 degrees for each lower orbit. Depending on the vertical height of the structure 12 and the required resolution, in the order of about at least 5 to 10 of the inner orbit may be flown. Each of the series of orbits may be flown at about the same vertical height intervals to provide for pairs of overlapping orbits at each vertical height along the vertical structure 12.

[0073] The method 210 and system 10 provide plurality of overlapping images from each of the plurality of overlapping orbits along the vertical height of the vertical structure 10 that are envisaged to provide sufficient resolution to be processed by advanced photogrammetry software, such as that available from Bentley Systems TM to provide digital models of tower structures have resolutions in the order of 1mm or better on structural members of the structure 12.

[0074] Advantageously, there has been described a system and methods for obtaining digital images of the vertical structure suitable to be process and provide high resolutions models of the vertical structure for digital asset management. In particular, the methods include capturing images at orbits that vary in the lateral distance from the tower, such as by using inner and outer orbits, to provide pairs of images at varying lateral distances and captured at, preferably, different angles. This assists allows the inner orbits to have the camera focussed toward the structure and the outer orbit to be focussed more downwardly toward the ground for geo-referencing. This also assists to improve accuracy and assist to reduce any blocking and reflection of internal and external members of the vertical structure.

[0075] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0076] The reference in this specification to any known matter or any prior publication is not, and should not be taken to be, an acknowledgment or admission or suggestion that the known matter or prior art publication forms part of the common general knowledge in the field to which this specification relates.

[0077] While specific examples of the invention have been described, it will be understood that the invention extends to alternative combinations of the features disclosed or evident from the disclosure provided herein.

[0078] Many and various modifications will be apparent to those skilled in the art without departing from the scope of the invention disclosed or evident from the disclosure provided herein.

Claims

The claims defining the Invention are as follows:

1. A method for collecting photographic data of a vertical structure using an unmanned aerial vehicle carrying an image capturing device for input to a model, the method including the steps of: flying the unmanned aerial vehicle above the vertical structure so as to determine a vertical axis about which one or more first orbits and one or more second orbits are to be flown; flying the unmanned aerial vehicle in a first flight path in the one or more first orbits about the vertical structure and capturing a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and flying the unmanned aerial vehicle in a second flight path in the one or more second orbits about the vertical structure, the one or more second orbits being at least partially inward of the one or more first orbits toward the vertical structure, and capturing a plurality of overlapping images of the vertical structure with the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle, wherein the first and second flight paths respectively include pluralities of each of the first and second orbits made vertically along the vertical structure.

2. The method according to claim 1, wherein the pluralities of each of the first and second orbits are made at pre-determined discrete vertical increments along the vertical structure, and wherein the plurality of overlapping images are captured at each of the at pre-determined discrete vertical increments.

3. The method according to claim 2, wherein the discrete vertical increments of the each of the first and second orbits are substantially the same so as to provide pluralities of images captured outwardly and inwardly relative to one other at substantially the same vertical height.

4. The method according to claim 1, wherein the pluralities of each of the first and second orbits are made at pre-determined continuous vertical increments along the vertical structure so as to form first and second spiral orbits.

5. The method according to claim 1, wherein the first orbit is initiated from a location toward a top of the vertical structure and the first angle is at least initially set to capture the entire vertical structure and the ground surface.

6. The method according to claim 1, wherein the first angle is in the range of about 45 to 60 degrees downward relative to the horizontal.

7. The method according to claim 6, wherein the first angle is varied as the first flight path moves along the vertical structure.

8. The method according to claim 1, wherein the first orbit has a radius of between about 2/3 and 1 1/3 of the height of the vertical structure.

9. The method according to claim 1, wherein the second angle is in the range of about 0 to 10 degrees upward or downward from the horizontal.

10. The method according to claim 9, wherein the second angle is varied as the second flight path moves along the vertical structure.

11. The method according to claim 1, wherein the second orbit has a radius of between about 1/3 and 2/3 of the height of the vertical structure.

12. The method according to claim 1, wherein the first orbit is an outer orbit and the second orbit is an inner orbit, the inner and outer orbits being substantially non overlapping.

13. The method according to claim 1, wherein the first and second orbits are circular.

14. The method according to claim 1, wherein one or both of the first and second orbits are elliptical.

15. The method according to any one of claims I to 14, wherein the method includes the steps of: drnirmininc nt lonet twn nffezt nyp- that qri pqnph 1sternllI nffezt frnm n vertical axis of the vertical structure and from one another; and wherein the first and second orbits are flown about respective ones of the at least two offset axes.

16. The method according to any one of claims I to 14, wherein the method includes the steps of: determining a plurality of offset axes that are each laterally offset from a vertical axis of the vertical structure and from one another; and wherein the first and second orbits are provided in the form of a plurality of orbits that are flown about respective ones of the plurality of offset axes.

17. The method according to any one of the previous claims, wherein the vertical structure is a tower.

18. A system including an unmanned aerial vehicle and an image capturing device configured to perform a method as defined in any one of claims I to 17.

19. A digital model of a vertical structure formed substantially with images captured by a method as defined in any one of claims I to 17.

20. A collection of digital images including images captured by a method as defined in any one of claims I to 17.

21. A system including unmanned aerial vehicle and an image capturing device for collecting photographic data of a vertical structure for input to a model, the system being configurable to: fly the unmanned aerial vehicle above the vertical structure so as to determine a vertical axis about which one or more first orbits and one or more second orbits are to be flown; fly the unmanned aerial vehicle in a first flight path in the one or more first orbits about the vertical structure and capturing a plurality of overlapping images of the vertical structure with the image capturing device, the image capturing device being at a first angle so as to capture at least some of the vertical structure and at least some of a ground surface proximate the vertical structure; and fly the unmanned aerial vehicle in a second flight path in the one or more second orbits about the vertical structure, the one or more second orbits being at least capturing a plurality of overlapping images of the vertical structure with the image capturing device being at a second angle, the second angle being relatively toward the vertical structure in comparison to the first angle, wherein the first and second flight paths respectively include pluralities of each of the first and second orbits made vertically along the vertical structure.