Comparison Testing of an Underwater Laser Scanner

Comparison Testing of an Underwater Laser Scanner Summary of Co-op Work Term Project, Fall 2011 Colin MacKenzie Dalhousie University Department of Mec...
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Comparison Testing of an Underwater Laser Scanner Summary of Co-op Work Term Project, Fall 2011 Colin MacKenzie Dalhousie University Department of Mechanical Engineering Anna Crawford DRDC – Atlantic Research Centre

Defence Research and Development Canada Scientific Report DRDC-RDDC-2015-R061 May 2015

IMPORTANT INFORMATIVE STATEMENTS This report documents work performed in partial fulfillment of the requirements of a Co-op work term by the Department of Mechanical Engineering, Dalhousie University, Halifax, N.S.

© Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2015 © Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale, 2015

Abstract .. Mine and Harbour defense is a key role for Canada’s Navy. Part of this task entails developing and implementing Mine Counter Measures (MCM) that allow ships and submarines to navigate safely through whatever bodies of water their orders take them. A crucial component of this process is the detection and identification of mine like objects. Currently Autonomous Underwater Vehicles (AUVs) utilize a range of sonar scanners to locate and identify shapes that may or may not be dangerous. An advantage of sonar scanners is their ability to send out signals and form pictures in a fraction of a second. The primary challenge with sonar based systems is in properly identifying objects in the seabed images they generate. In order to be reasonably sure that a section of water is safe the sensitivity of a sonar device must be high, but this greater sensitivity results in an increased number of false positives, greatly lengthening the time taken to verify or clear a path. The purpose of this report was to examine how the ULS-100 underwater laser scanner from 2G Robotics compares to standard sonar scanners. The laser scanner produces far more detailed images of objects on the ocean floor than sonar based scanners. It creates a point cloud that can be rotated in virtual 3D space and can better measure features to more accurately identify mines. The disadvantage of this option is that the laser scanner takes much longer to form an image than sonar scanners. The study comparison concluded the laser scanner’s increased run time meant it was not a feasible replacement for sonar devices, but both technologies used in combination could lead to improved overall MCM operations.

Significance to Defence and Security This report describes a comparison between a new laser scanner system and imaging sonars which are more commonly utilized for inspection tasks under water that require high spatial resolution. The results of the comparison indicate that while the measurements by the laser scanner are very precise, it takes considerable time to complete a scan, which would be problematic for real MCM applications. A combined approach is suggested for use of this system, with sonar for coverage of wider areas and initial location, then laser scanner for detailed identification.

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Résumé … La défense portuaire et la protection antimines sont des rôles clés de la Marine canadienne. L’une des tâches consiste à élaborer et à mettre en œuvre des mesures de lutte contre les mines (LCM) en vue de permettre aux navires et sous-marins qui en ont reçu l’ordre de naviguer sans danger dans toute masse d’eau. À cette fin, il est nécessaire de détecter et d’identifier les objets ressemblant à des mines. À l’heure actuelle, les véhicules sous-marins autonomes (VSA) localisent et identifient des formes potentiellement dangereuses à l’aide d’un éventail de scanneurs sonar, lesquels peuvent émettre des signaux et former des images en une fraction de seconde. Dans le cas des systèmes radar, le principal défi est d’identifier correctement les objets sur des images générées du fond marin. Afin d’offrir une certitude raisonnable qu’un secteur marin est sûr, la sensibilité du dispositif radar doit être élevée. Toutefois, cette sensibilité entraînera un plus grand nombre de faux positifs et augmentera donc considérablement le temps nécessaire pour s’assurer que la voie est libre ou se frayer un chemin. Le présent rapport visait à comparer le scanneur laser sous-marin ULS-100 de 2G Robotics avec les scanneurs sonar standard. Le scanneur laser produit des images beaucoup plus détaillées des objets sur le fond marin. Il génère un nuage de points, qui peut être tourné dans un espace virtuel 3D, et permet de mieux mesurer les caractéristiques afin d’identifier les mines avec davantage d’exactitude. Toutefois, le scanneur laser nécessite plus de temps pour produire une image que les scanneurs sonar. L’étude comparative a permis de conclure que le scanneur laser ne pouvait remplacer les dispositifs sonar en raison de sa plus longue durée d’exécution, mais qu’une combinaison des deux technologies permettrait d’améliorer les opérations de LCM en général.

Importance pour la défense et la sécurité Le présent rapport porte sur la comparaison d’un nouveau scanneur laser avec des sonars d’imagerie plus fréquemment utilisés dans le cadre de tâches d’inspection sous-marine nécessitant une limite de résolution spatiale élevée. Les résultats obtenus montrent que, malgré la très haute précision des mesures prises par le scanneur laser, le temps considérable qu’il met pour effectuer un balayage complet pourrait être problématique dans le cas d’applications de réelle LCM. Une méthode combinée est recommandée : un sonar servant à couvrir les zones plus vastes et l’emplacement initial et le scanneur laser pour identifier plus en détail.

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Table of Contents Abstract .. ........................................................................................................................................ i Significance to Defence and Security............................................................................................... i Résumé … ....................................................................................................................................... ii Importance pour la défense et la sécurité ........................................................................................ ii Table of Contents ........................................................................................................................... iii List of Figures ................................................................................................................................ iv List of Tables ................................................................................................................................... v Acknowledgements ........................................................................................................................ vi 1 Introduction ............................................................................................................................... 1 2

ULS-100 Underwater Laser Scanner ........................................................................................ 2

3

Mine-Shaped Targets ................................................................................................................ 3 3.1 Mine Object 1 .................................................................................................................. 3 3.2 Mine Object 2 .................................................................................................................. 3 3.3 Mine Object 3 .................................................................................................................. 4 3.4 Mine Object 4 .................................................................................................................. 5 3.5 Mine Object 5 .................................................................................................................. 5 3.6 Mine Object 6 .................................................................................................................. 6

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Description of the Testing ......................................................................................................... 8

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Sonar Scanners .......................................................................................................................... 9 5.1 BlueView P450 Sonar ..................................................................................................... 9 5.2 DIDSON 300 ................................................................................................................. 10 ULS-100 Underwater Laser Scanner—Results....................................................................... 12 6.1 Mine Object 1 ................................................................................................................ 12 6.2 Mine Object 2 ................................................................................................................ 12 6.3 Mine Object 3 ................................................................................................................ 13 6.4 Mine Object 4 ................................................................................................................ 14 6.5 Mine Object 5 ................................................................................................................ 15 6.6 Mine Object 6 ................................................................................................................ 15

6

7

Conclusion and Recommendations ......................................................................................... 17

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List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13

The ULS-100 laser scanner head. . . . . . . . . . . . . . . . . . . . . . .2 . . . . . . Object 1: (a) top view; (b) oblique view. . . . . . . . . . . . . . . . . . . .3 . . . . . . Object 2: (a) top view; (b) side view. . . . . . . . . . . . . . . . . . . . . .4 . . . . . . Object 3: (a) top view; (b) oblique view. . . . . . . . . . . . . . . . . . . .4 . . . . . . Object 4: (a) top view; (b) oblique view. . . . . . . . . . . . . . . . . . . .5 . . . . . . Object 5: (a) top view; (b) oblique view. . . . . . . . . . . . . . . . . . . .6 . . . . . . Object 6: (a) top view; (b) oblique view. . . . . . . . . . . . . . . . . . . .6 . . . . . . Rotating platform with objects. . . . . . . . . . . . . . . . . . . . . . . .8 . . . . . . BlueView P450 sonar. . . . . . . . . . . . . . . . . . . . . . . . . . . .9 . . . . . . BlueView P450 sonar images: (a ) view 1; (b) view 2; (c) view 3. . . . . . . . 10 . . . . . . . DIDSON 300 sonar. . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 . . . . . . . DIDSON 300 sonar images: (a) view 1; (b) view 2; (c) view 3. . . . . . . . . 11 . . . . . . .

Figure 14

Object 1: (a) view 1; (b) view 2. . . . . . . . . . . . . . . . . . . . . . . 12 . . . . . . . Object 2: (a) view 1; (b) view 2. . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . .

Figure 15

Object 3: (a) view 1; (b) view 2. . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . .

Figure 16 Figure 17

Object 4: (a) view 1; (b) view 2. . . . . . . . . . . . . . . . . . . . . . . 14 . . . . . . . Object 5: (a) view 1; (b) view 2. . . . . . . . . . . . . . . . . . . . . . . 15 . . . . . . .

Figure 18

Object 6: (a) view 1; (b) view 2. . . . . . . . . . . . . . . . . . . . . . . 16 . . . . . . .

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List of Tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 Table 12

Object 1 measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . .3 . . . . . . Object 2 measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . .4 . . . . . . Object 3 measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . .5 . . . . . . Object 4 measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . .5 . . . . . . Object 5 measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . .6 . . . . . . Object 6 measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . .7 . . . . . . Object 1 laser scanner measurements, compared with physical measurements. . . . . . . . . . . . . . . . . . . . . . . Object 2 laser scanner measurements, compared with physical measurements. . . . . . . . . . . . . . . . . . . . . . . Object 3 laser scanner measurements, compared with physical measurements. . . . . . . . . . . . . . . . . . . . . . . Object 4 laser scanner measurements, compared with physical measurements. . . . . . . . . . . . . . . . . . . . . . . Object 5 laser scanner measurements, compared with physical measurements. . . . . . . . . . . . . . . . . . . . . . . Object 6 laser scanner measurements, compared with physical measurements. . . . . . . . . . . . . . . . . . . . . . .

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12 . . . . . . . . . . 13 . . . . . . . . . . 14 . . . . . . . . . . 14 . . . . . . . . . . 15 . . . . . . . . . . 16 . . . . . . . . . .

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Acknowledgements This report documents work performed in partial fulfillment of the requirements of a Co-op work term, as specified by the Department of Mechanical Engineering, Dalhousie University, Halifax, N.S., under the supervision of Dr Anna Crawford, DRDC Atlantic. It also fulfills the testing and evaluation requirement of the Canadian Innovation Commercialization Program (CICP), under which DRDC Atlantic obtained the ULS-100 system from 2G Robotics Inc., Waterloo, Ontario.

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Introduction

The Mine and Harbour Defence group at DRDC Atlantic performs research and development into areas of defence and security supporting the Royal Canadian Navy (RCN). There are frequent Naval requirements for underwater inspection, from monitoring of hulls for foreign objects to routine maintenance surveys of jetties. These tasks have historically been performed visually by divers and were very time consuming. With improvements to sonar resolving power and portability, divers have more recently been able to use high frequency imaging sonar systems to assist in conditions of poor visibility or where there is risk to personnel necessitating stand-off. The system which has been tested and reported on here is a further advance in underwater laser scanning, which offers the potential for much better spatial resolution in measurement of objects. The ULS-100 Laser Scanner was obtained through the Canadian Innovation Commercialization Program (CICP). The ULS-100 Laser Scanner system has been tested at DRDC in comparison with several commercial high resolution imaging sonar systems currently in use by divers in real inspection applications on realistic mine-like objects obtained from the RCN Fleet Diving Unit.

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ULS-100 Underwater Laser Scanner

The ULS-100 Underwater Laser Scanner was developed by 2G Robotics Inc. Waterloo, Ont. It produces 3D point clouds by scanning the surface of underwater objects. By emitting a line of laser light onto the target surface and then capturing the reflected light using an optical detector, a profile of points is captured. Using a rotary actuator, the head of the ULS-100 can be turned to capture a series of adjacent profiles to build up a 3D point cloud representation. The point clouds consist of a collection of points in 3D space that comprehensively define the surface of the scanned objects. Unlike terrestrial laser measurement systems, the ULS-100 uses a triangulation approach and algorithms for filtering noise due to debris floating in the water.

Figure 1: The ULS-100 laser scanner head. Through the Canadian Innovation Commercialization Program (CICP), DRDC Atlantic obtained a ULS-100 system, with the proviso that detailed testing of the scanner be performed. Various targets were used in the testing including Limpet mine-like replicas borrowed from the CF Fleet Diving Unit (FDU) Atlantic and other objects scrounged or constructed to represent Improvised Explosive Devices (IED’s). In-air measurements were made of the targets using precision equipment borrowed from the DRDC Atlantic machine shop. The aspect of the laser system’s performance of particular interest during testing was its basic measurement accuracy. The testing was performed in the Calibration Tank facility at DRDC Atlantic, a fresh water tank 7.3 m in diameter and 4.5 m deep, equipped with rotating-translating mounts for test equipment. Comparison measurements were made underwater using imaging sonar (DIDSON 300 or BlueView, p. 450).

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Mine-Shaped Targets

Six objects were selected to represent mines for testing the sonar scanners and the laser scanner. Some of the dummy mines were borrowed from the Fleet Diving Unit – Atlantic, while others were chosen for unique features expected to test the abilities of the scanners. Below are brief descriptions and images of each “mine” accompanied by a table of the object’s key dimensions taken with a digital vernier caliper.

3.1

Mine Object 1

The first “mine” chosen was the aluminum cylinder seen below. It was expected to be challenging for sonar scanners to make it out because of its curved, highly reflective surface, and it provided the laser scanner with different diameters to compare against the caliper measurements

(a)

(b)

Figure 2: Object 1: (a) top view; (b) oblique view. Table 1: Object 1 measurements.

3.2

Feature

Measurement (mm)

Base diameter Outer shaft diameter Inner shaft diameter Center hole Screw holes Total height

146.05 100.86 86.36 28.26 3.87 147.82

Mine Object 2

Mine Object 2 had a more traditional mine shape and while it was significantly larger than some of the other test objects, its dome like surface was a challenge for the sonar scanners because of its reflectivity. DRDC-RDDC-2015-R061

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(a)

(b)

Figure 3: Object 2: (a) top view; (b) side view. Table 2: Object 2 measurements.

3.3

Feature

Measurement (mm)

Diameter Height

254.18 116.39

Mine Object 3

Mine Object 3, the dummy clam mine, is designed to be placed on ships. Its curved surface makes it difficult to detect with sonar scanners when being viewed from the side, but its flat ends offered opportunities for the sonar to discover. It provided only a few dimensions for the laser scanner to measure but they were easily captured.

(a)

(b)

Figure 4: Object 3: (a) top view; (b) oblique view.

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Table 3: Object 3 measurements.

3.4

Feature

Measurement (mm)

Total length Total width Main length Width of ends Height Total length

266.04 111.86 191.21 70.56 34.31 266.04

Mine Object 4

Mine Object 4 was a plastic object chosen for its various circular dimensions. Its purpose was to test the laser scanner’s ability to measure features at different depths within an object.

(a)

(b)

Figure 5: Object 4: (a) top view; (b) oblique view. Table 4: Object 4 measurements.

3.5

Feature

Measurement (mm)

Base diameter Main diameter Eyes Pupils Mouth Eye depth

116.81 101.23 45.02 19.63 10.88 6.57

Mine Object 5

Mine Object 5 was a piping part chosen because its intricate shape with many flat edges allowed it to remain within view of the sonar scanners at all times while the platform was rotating. DRDC-RDDC-2015-R061

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(a)

(b)

Figure 6: Object 5: (a) top view; (b) oblique view. Table 5: Object 5 measurements.

3.6

Feature

Measurement (mm)

Full length Diameter Full diagonal Cut out length Cut out width Total height

145.85 128.07 151.84 44.60 61.98 67.51

Mine Object 6

Mine Object 6 was chosen specifically to test the laser scanner’s ability to “see” target detail. It was not fixed to the rotating table but was suspended in the water. The object had several very small features, difficult for sensors to pick up, the other objects did not have. This tested the laser scanner’s accuracy with details.

(a)

(b)

Figure 7: Object 6: (a) top view; (b) oblique view.

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Table 6: Object 6 measurements. Feature

Measurement (mm)

Outer diameter Inner diameter Fin length Fin width Height

147.15 141.86 30.86 3.26 45.52

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4

Description of the Testing

The process of testing the objects was performed on a circular rotational surface that was lowered into the DRDC fresh water testing tank on a rotation shaft. The sonar and laser scanners were fixed to a pan-tilt motor within the tank. Being able to maneuver the scanners easily while being able to rotate the tray of objects allowed for optimal scanning of the images.

Figure 8: Rotating platform with objects.

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Sonar Scanners

This section shows two sonar scanners used in this testing process, the BlueView P450 and the DIDSON 300 1.8 MHz sonar scanner.

5.1

BlueView P450 Sonar

Figure 9: BlueView P450 sonar. The BlueView P450 is an imaging sonar that operates with a frequency of 450 kHz and reveals the location of underwater objects within a small range, from 0.5 m to 50 m. While the frequency is not high enough to show intricate definition of the objects it is able to differentiate between two or more targets even if they are as small as six inches in size and only six inches apart. This level of clarity has limited value identifying what a specific object is but can identify that an object is present. The figures below show BlueView P450 sonar images of the test table and targets at three different stages of the table’s rotation. The 3 positions chosen were the table: 1. In its initial position; 2. After rotating 120 degrees; and 3. After rotating180 degrees from its initial position.

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(a)

(b)

(c)

Figure 10: BlueView P450 sonar images: (a ) view 1; (b) view 2; (c) view 3. It can be seen from these figures that the targets on the platform stand out as separate objects, but it is impossible to make out what the objects are or make out any of their features.

5.2

DIDSON 300

Figure 11: DIDSON 300 sonar. The DIDSON 300 sonar scanner is a much higher resolution sonar than the BlueView P450. It operates at a frequency of 1.8 MHz which gives its’ images much higher definition, allowing different objects to be clearly identified when viewed together. Its range is similar to the BlueView P450 varying from 0.5 m to 20 m. The better scan definition makes the DIDSON sonar preferable for mine counter measure applications because its superior ability to identify specific targets drastically cuts down the number of false positives that will otherwise occur over the course of a mission. The figures below are sonar images taken with the DIDSON 300 of the same table of objects noted above. The three positions shown are the same positions shown for the BlueView P450. This allows for an easy direct comparison of the two sonar scanners.

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(a)

(b)

(c)

Figure 12: DIDSON 300 sonar images: (a) view 1; (b) view 2; (c) view 3. As shown in the above images there is a significant improvement in the amount of image detail compared to the BlueView. With an operating frequency of 1.8 MHz the DIDSON is clearly the superior sonar. Even so much of the objects detail is blocked by shadows and their exact shape and fine dimensions are still difficult to determine.

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6

ULS-100 Underwater Laser Scanner—Results

Images from the ULS-100 laser scanner test using the 6 mine targets described earlier are shown below. Target dimensions found using the 2G Robotics Scanner Viewer software’s measuring tool are also presented. The Scanner Viewer software required an updated calibration file for accurate results, so that the measurements from the scans are off by factors in the horizontal and vertical directions.

6.1

Mine Object 1

Mine Object 1 illustrates some of the challenges faced by laser scanners. The scanner had trouble with objects with a sharp vertical drop as this cylinder shaped object does. It also was not able to pick up edges that had a highly reflective surface unless they were viewed straight on. Since Mine Object 1’s surfaces are completely shiny, this made it very difficult for the scanner to obtain a measurable surface.

(a)

(b)

Figure 13: Object 1: (a) view 1; (b) view 2. Table 7: Object 1 laser scanner measurements, compared with physical measurements. Feature Base diameter Outer shaft diameter Inner shaft diameter Center hole Screw holes Total height

6.2

ULS scan (mm) 72 68 Not found Not found Not found 87

Measurement (mm) 146.05 100.86 86.36 28.26 3.87 147.82

Mine Object 2

The laser scanner was more successful with the dome shaped target because its height and diameter were more viewable to the laser. The downside of the scanner in this situation was similar to Mine Object 1where the shiny curved surfaces reflected poorly towards the scanner. 12

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When objects with shiny surfaces are scanned with a laser only perpendicular surfaces reflect back. With Mine Object 2 a more complete image was formed by taking two separate scans and laying them on top of each other. This ability to shift the scans in 3D space was found to be very useful.

(a)

(b)

Figure 14: Object 2: (a) view 1; (b) view 2. Table 8: Object 2 laser scanner measurements, compared with physical measurements.

6.3

Feature

ULS scan (mm)

Measurement (mm)

Diameter Height

183.0 87.0

254.18 116.39

Mine Object 3

The Mine Object 3 scan provided similar results as the first 2 tests. The base edges were found to be clearly defined and easily measured, as was the target’s height when scanned from directly above the object.

(a)

(b)

Figure 15: Object 3: (a) view 1; (b) view 2.

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Table 9: Object 3 laser scanner measurements, compared with physical measurements.

6.4

Feature

ULS scan (mm)

Measurement (mm)

Total length Total width Main length Width of ends Height Total length

200.00 88.0 141.0 55.0 22.0 Not found

266.04 111.86 191.21 70.56 34.31 266.04

Mine Object 4

Mine Object 4 did not have reflective surfaces, its flat plastic body allowed for a clear image to be taken by the laser allowing for accurate measurements of the cut outs. The testing showed the most challenging dimension for the scanner to fix was the depth of holes not completely drilled through.

(a)

(b)

Figure 16: Object 4: (a) view 1; (b) view 2. Table 10: Object 4 laser scanner measurements, compared with physical measurements.

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Feature

ULS scan (mm)

Measurement (mm)

Base diameter Main diameter Eyes Pupils Mouth Eye depth Total height

89.0 74.0 31.0 19.0 10.0 5.0 29.0

116.81 101.23 45.02 19.63 10.88 6.57 Not measured

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6.5

Mine Object 5

Mine Object 5 fine had a semi-shiny surface, with some of its reflective coating worn off. This surface, combined with the fact that most of the object’s detail was oriented perpendicular to the scanner, made the top dimensions easy for the scanner to capture. The isometric view however showed up as a blank patch because the details’ drop is too steep.

(a)

(b)

Figure 17: Object 5: (a) view 1; (b) view 2. Table 11: Object 5 laser scanner measurements, compared with physical measurements.

6.6

Feature

ULS scan (mm)

Measurement (mm)

Full length Diameter Full diagonal Cut out length Cut out width Total height

Not found 91.0 111.0 37.0 46.0 37.0

145.85 128.07 151.84 44.60 61.98 67.51

Mine Object 6

Mine Object 6 was not scanned using sonar. It was fixed in the water by strings to avoid providing a background. The laser scanner results were positive in that some of the smaller fin details on the target could be viewed and the object easily identified. Unfortunately the scan was not clear enough to measure the target’s smaller details, although larger features (ex. diameter and height) were found.

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(a)

(b)

Figure 18: Object 6: (a) view 1; (b) view 2. Table 12: Object 6 laser scanner measurements, compared with physical measurements.

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Feature

ULS scan (mm)

Measurement (mm)

Outer diameter Inner diameter Fin length Fin width Height

Not found 49 Not found Not found Not found

147.15 141.86 30.86 3.26 45.52

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Conclusion and Recommendations

Of the two sonar scanners the DIDSON 300 operating at a frequency of 1.8 MHz was found to provide a greater discrimination ability than the BlueView P450 operating at 450 kHz. The increased frequency provides a dramatic increase in scan definition allowing for easier identification of potential mines and improved measurement of target details. The outdated calibration file caused all dimension measurements to be off by factors up to 2.8—it was not possible to obtain a new calibration file before the end of the semester. The laser scanner was found to have difficulty with certain objects, specifically its ability to form images from reflective surfaces and objects with sharp drop offs. It also took more time than sonar based scanners to produce its images. However it was found to produce much more accurate scans than sonar scanners with some targets. While the sonar scanners’ speed makes it an ideal tool for an initial scan for potential threats, it will always generate false positives. For this reason it is recommended that an effective MCM strategy be based on a composite approach using sonar based scanners such as the DIDSON to select areas of interest followed by laser based scanners to verify whether the object is in fact a threat.

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DRDC – Atlantic Research Centre Defence Research and Development Canada 9 Grove Street P.O. Box 1012 Dartmouth, Nova Scotia B2Y 3Z7 Canada

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Comparison Testing of an Underwater Laser Scanner : Summary of Co-op Work Term Project, Fall 2011 4.

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MacKenzie. C.; Crawford, A. 5.

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Unlimited 12. DOCUMENT ANNOUNCEMENT (Any limitation to the bibliographic announcement of this document. This will normally correspond to the Document Availability (11). However, where further distribution (beyond the audience specified in (11) is possible, a wider announcement audience may be selected.))

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13. ABSTRACT (A brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly desirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the security classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C), (R), or (U). It is not necessary to include here abstracts in both official languages unless the text is bilingual.)

Mine and Harbour defense is a key role for Canada’s Navy. Part of this task entails developing and implementing mine counter measures (MCM) that allow ships and submarines to navigate safely through whatever bodies of water their orders take them. A crucial component of this process is the detection and identification of mine like objects. Currently Autonomous Underwater Vehicles (AUVs) utilize a range of sonar scanners to locate and identify shapes that may or may not be dangerous. An advantage of sonar scanners is their ability to send out signals and form pictures in a fraction of a second. The primary challenge with sonar based systems is in properly identifying objects in the seabed images they generate. In order to be reasonably sure that a section of water is safe the sensitivity of a sonar device must be high, but this greater sensitivity results in an increased number of false positives, greatly lengthening the time taken to verify or clear a path. The purpose of this report was to examine how the ULS-100 underwater laser scanner from 2G Robotics compares to standard sonar scanners. The laser scanner produces far more detailed images of objects on the ocean floor than sonar based scanners. It creates a point cloud that can be rotated in virtual 3D space and can better measure features to more accurately identify mines. The disadvantage of this option is that the laser scanner takes much longer to form an image than sonar scanners. The study comparison concluded the laser scanner’s increased run time meant it was not a feasible replacement for sonar devices, but both technologies used in combination could lead to improved overall MCM operations. ---------------------------------------------------------------------------------------------------------------

14. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Technically meaningful terms or short phrases that characterize a document and could be helpful in cataloguing the document. They should be selected so that no security classification is required. Identifiers, such as equipment model designation, trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus, e.g., Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus identified. If it is not possible to select indexing terms which are Unclassified, the classification of each should be indicated as with the title.)

Laser scanner, measurements, calibration.