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American Fisheries Society Symposium 64:191–200, 2008© 2008 by the American Fisheries Society

Assessment of Nearshore Artificial Reefs in Okaloosa County, Florida by Volunteers Using Side Scan Sonar

L. Scott JackSon*University of Florida Sea Grant Extension, Okaloosa/Walton Counties

732 North 9th Street, DeFuniak Springs, Florida 32433, USA

Gary H. ParSonS, GLen DaviS, anD ken croSbyEmerald Coast Reef Association

1781 Union Avenue, Niceville, Florida 32578, USA

Abstract.—The sea floor in the western panhandle region of Florida consists main-ly of unconsolidated sediments, causing the counties in this area to support the cre-ation of artificial reefs to provide habitat for local fish populations. Several issues have emerged with these sites, including inaccurate coordinates for the original deployment of materials, movement of reef materials by hurricane wave action, structure failure, and deterioration.

Emerald Coast Reef Association, a local group of fishers and divers, partnered with Florida Sea Grant Extension to conduct a side scan sonar survey of selected nearshore reefs in Okaloosa County during 2005. This article summarizes survey methods using recent innovations in side scan sonar technology as well as the survey results.

Information systems in conjunction with the use of low-frequency side scan sonar allowed for accurate location of previously deployed reef materials. High-frequency scanning further refined reef material location and was used to evaluate reef condi-tion. Side scan sonar surveys provided the foundation for future monitoring activities such as video and diving assessments.

A number of the structures detected during the survey illustrate valuable lessons for artificial reef deployment and management. Care in the placement of reef materi-als during deployment needs to be prioritized in order for structures to function as they were originally designed. Cylindrical objects need to be deployed in deeper waters and modified to improve storm stability. Reef deployments made during the era of Long Range Navigation may not have been recorded accurately compared to today’s standards. Accurately calibrated navigational instruments and professional records are essential tools for future reef managers.

Our experience from these surveys also indicates it may not be necessary to locate all lost reefs, even though fishermen and divers may benefit. Previous research studies suggest that lost reefs are utilized as de facto refugia, potentially benefiting fisheries stocks. Nearshore, however, it is prudent to manage all reef structures closely due to the presence of natural reefs, trawling activity, and navigational lanes.

The success of this survey suggests skilled volunteer groups can play a larger role in artificial reef management and monitoring. The capacity to execute these types of projects at the local level complements traditional research information from uni-versities and government entities and is of great value to local artificial reef program managers.

* Corresponding author: lsj@ufl.edu

192 JackSon et aL.

BackgroundThe northwest Florida counties of Es-

cambia, Santa Rosa, Okaloosa, Walton, and Bay attract 5–13 million overnight visitors annually (Bell et al. 1998; J. Klein, North-west Florida. University of West Florida Haas Center for Business Research and Economic Development, personal communication). Ap-proximately 10% of all visitors engage in rec-reational boating activities, including fishing and diving (Bell et al. 1998). Additionally, a combined charter fleet of approximately 250 vessels operates in the waters off of Pensacola, Destin, and Panama City (Florida Depart-ment of Highway Safety and Motor Vehicles 2007; L. S. Jackson, B. J. Cameron, University of Florida—IFAS Sea Grant Extension, and R. K. Turpin, Division of Marine Resources— Escambia County, personal communication). Marinas, dive shops, tackle shops, lodging, restaurants, and other retail businesses are economically dependent on these fishing and diving charters.

Despite this economic dependence on fishing resources, much of the sea floor in this region of Florida consists of sand and shell bottom occasionally interrupted by low-relief limestone ridges. The paucity of natural reef habitats has led local governments and indi-viduals to support the use of artificial reefs. Bell et al. (1998) estimated that the economic benefit attributed to artificial reefs in north-west Florida totaled $414 million in 1997.

Okaloosa County operates one of the most active artificial reef deployment programs in Florida. From the mid-1980s through the mid-1990s, Okaloosa County artificial reef deploy-ments were conducted in small permitted ar-eas within 2–9 km of the entrance to the East Pass near Destin, Florida (Figure 1). More re-cently, the county’s focus on deployment has changed to the large area artificial reefs sites (LAARS) from 28 to 46 km offshore. Never-theless, the older nearshore reefs continue to be important sites for recreational fishermen. These sites are used by small private boats and charter boats operating half-day trips. How-ever, there are several issues associated with these older sites, including the lack of accu-

rate Global Positioning System (GPS) coor-dinates for the original deployed materials, movement of reef materials by hurricane wave action, structural failure, and deterioration.

Emerald Coast Reef Association (ECRA), a grassroots organization, partnered with Flor-ida Sea Grant Extension to conduct an assess-ment of several nearshore reefs in Okaloosa County during 2005. Composed of interested and motivated members of the local fishing and diving community, ECRA conceived of and planned these survey activities. They also provided the principal investigator, divers, technicians, videographers, vessels, and other necessary equipment to complete the project. Florida Sea Grant provided fiscal oversight, technical support, quality assurance proce-dures, data analysis, and reporting.

Side scan sonar (SSS) was a valuable in-strument in this survey and was utilized to lo-cate previously deployed artificial reefs. These reefs had been moved as a result of tropical cyclones or locations were inaccurately re-corded at the time of deployment when Long Range Navigation (LORAN) was the best available technology for determining position (Parsons et al. 2006).

Work was completed under a grant pro-vided by the Florida Fish and Wildlife Com-mission (FWC). Study costs were minimal compared to costs of original deployment and value to the recreational fishing community.

This article seeks to summarize the survey methods and results and highlight the value of volunteers and community organizations in increasing the capacity to locate, monitor, and assess artificial reefs. Additionally, the project demonstrates recent innovations in side scan sonar technology that make it possible for nongovernment organizations to use a power-ful tool formerly only available to the military, commercial industry, or ocean researchers.

MethodsInstrumentation

Side scan sonar is the method of choice for locating and mapping seafloor features. Historically, such instrumentation was oper-

193artificaL reef aSSeSSment uSinG SiDe Scan Sonar

Figure 1. Site map of scanned survey areas.

ated from large research vessels, which pro-vided a stable work platform, a work environ-ment protected from the elements and power winches, and other gear for deployment and retrieval of the towfish, which is the torpedo-shaped portion of the SSS system that oper-ates underwater (Figure 2). In the traditional research setting, sonar mapping operations are expensive and usually require university-level teams of technicians and scientists to op-erate and maintain the equipment and inter-pret the sonar imagery. Recently, at least one manufacturer has marketed a small, low-cost, lightweight side scan unit that can be deployed from small outboard powered vessels.

For this project, we rented the Imagenex Sportscan SSS model. The towfish body is small and can be used to accommodate ballast to control towfish altitude. The unit can be in-terfaced with a GPS and laptop PC. With the appropriate software, reasonably high quality

imagery can be obtained. Objects the size of typical commercial artificial reef units (1.8 3 1.8 m) can be detected and located within the accuracy of the GPS units. This is typically plus or minus 0.002 min (3.7 m).

Imagenex software was used to record im-ages and GPS coordinates of objects detected by the sonar unit. The location of objects was determined using the survey boat’s fixed-mount GPS unit with a data feed to the Ima-genex software running on a laptop PC that met the minimum 100-MHz processor speed and 1-GB storage capacity (the system require-ments are mainly for the generation of sonar images). The resulting data file integrated the sonar images, the GPS coordinates, and the speed and direction of the tow vessel. The re-corded GPS coordinates of objects were auto-matically translated by the computer software to account for the difference between the GPS antenna location on the vessel, the per-

194 JackSon et aL.

pendicular offset distance of the object from the vessel path, and the towfish distance be-hind the vessel, also referred to as the towfish layback.

Accuracy of an object’s calculated loca-tion is a function of the operating range of the sonar, accuracy of the towfish layback and altitude estimation, and the absolute accuracy of the GPS. When operating the SSS at low frequency (330 kHz) and 122-m range, we es-timated the accuracy of the system to be plus or minus 0.005 min (9.3 m). In high-frequen-cy (800-kHz) scans with 30-m range settings, we measured the accuracy by comparing the coordinates of objects from the side scan re-cord with the coordinates from a Wide Area Augmentation System (WAAS)-capable GPS; such units determine GPS coordinates that are corrected using ground-based reference stations. The WAAS GPS unit is mounted on the vessel, which locates the underwater ob-ject using conventional sonar and saves the location in the GPS memory. The average dif-ference between the initial SSS data records and final WAAS positions for 12 modules was less than 0.002 min (3.7 m).

Another GPS unit was used to store the area routes for the tow vessel and then to monitor the actual track and boat speed. Once the scans were complete, this GPS was also used in conjunction with a convention-al down-looking sonar (Furuno color LCD model FCV-600 L) to confirm the location of objects originally found using the side scan sonar. Dive video assessments were ob-

tained using a camcorder in an underwater housing.

Procedures

Preliminary testing was done to develop the operating parameters for the towfish and the towing vessel. Static deployment estab-lished the optimum towfish altitude for vari-ous depths, and dynamic towing was done to determine the weight placement and center of gravity for the attachment of the depres-sor wing to obtain towfish altitude above the seabed at several tow speeds. Low-frequency tows were conducted at range scales of 122 m on both sides of the towfish and at an al-titude of 12–15 m (approximately 10–20% of the range). Boat speed needed to achieve this altitude was approximately 6.5 km/h. Various targets were observed, including natural and artificial reef materials to provide a baseline for interpreting the imagery. High-frequency scans were conducted with the range setting of 30 m and the towfish altitude of 3–6 m. Boat speed had to be reduced to 3.7–4.6 km/h to achieve this altitude in water 21–24 m deep.

To begin a typical tow operation, the tow vessel was positioned several hundred yards east or west of the beginning of a site search area and taken out of gear. One or more routes were entered into the vessel GPS. For low-frequency scans, all routes were along lati-tudinal transects (extending east–west) and spaced 91 m apart. Since the scan range was set to 122 m on each side of the towfish to

Figure 2. Diagram of side scan sonar equipment provided with permission from State of Maine Geo-logical Survey. Side scan sonar images the seafloor surface by sending and receiving sound waves from either side of a submerged towfish with port and starboard transducers.

195artificaL reef aSSeSSment uSinG SiDe Scan Sonar

obtain at least 100% coverage, most objects were detected more than once. The towfish was manually lowered to a predetermined cable length. The operator attempted to steer the vessel to a course within 3 m or less of the selected route. At a zoom setting of 15 m, it is quite easy to see course deviations of 0.001 min or about 1.8 m. The helmsman was able to stay on course and maintain proper speed by using the GPS display as a guide along with a compass and bearing to stationary objects out-side the cockpit. The effects of minor prevail-ing ground swell and tide were easily accom-modated by adjusting engine rpm and course to correct for off-course drift. Holding course and speed in a chop became increasingly dif-ficult as the wave height increased and wave period decreased. Operations ceased when wave height exceeded 0.6–0.9 m.

As the vessel approached the end of the route, the GPS was used to locate the next route in sequence. As the towfish cleared the endpoint, the support crew stopped re-cording the scan data. The helmsman ma-neuvered to obtain alignment with the next route and the support crew entered the name of the next route on the lap top and began recording. As the helmsman approached the beginning of the next route, GPS was used again to closely track boat position along the route. Tracks (the actual courses of the ves-sel as recorded by the GPS) were stored and were recovered to compare with the planned survey routes as a quality assurance measure. Close encounters with boats fishing the artifi-cial reefs did occur and fish finders interfered with the sonar imagery, appearing as a scatter-ing of bright dots on the display. This interfer-ence was never enough to obscure the imag-ery. Resurveying of tracks was conducted any time a complete and accurate record was not obtained. Incidents that initiated resurveying of tracks included being pushed off course by other vessels, weather, wave action, electronic systems failure, and operator error.

Upon completion of a series of routes, the sonar imagery was downloaded by the project engineer and transmitted to project team members. Two team members read the imagery, noting the location of potential reef

materials. Notes were compared to arrive at a single set of reef objects and high-frequency scan routes were developed to more accurately locate and identify objects of interest. Objects located on the high-frequency scans were read as above. Coordinates were updated to reflect the greater accuracy of the high-frequency imagery and then the location was confirmed by vessels equipped with conventional down-looking sonar and GPS with WAAS capability. It was recommended that the locations con-firmed by WAAS be used in the published re-cords for recreational users.

Results and DiscussionSide scan sonar can be used to success-

fully document the location of reef materials. The interface with a GPS unit and laptop com-puter was straightforward and simple. The targeted artificial reefs for these side scan sur-veys were all large deployments representing a combined value of approximately $300,000. Prior to the study, total current inventory in the three nearshore sites surveyed consisted of 270 concrete modules, 24 army tank tur-rets, 3 army tanks, 44 liquid fuel storage tanks, 1 barge, and 7 piles of concrete (Horn 2007; Okaloosa County Online—Reefs/LORAN 22 June 2007, www.co.okaloosa.fl.us/reefsloran.html). From these reef deployments, an esti-mated 200 cast concrete reef modules and 44 liquid storage tanks were categorized as lost, missing, or never recorded. Finding their new positions was of great benefit for the small boat recreational angler or diver and accom-plished at a fraction of the cost of redeploy-ment of similar materials (the cost of this sur-vey was less than $12,000).

Reefs that were not located in this study should not necessarily be declared destroyed or ineffectual. As observed with the reefs that were located, fish are associated with all types of structure. Our experience from these sur-veys also indicates that it may not be necessary to locate all lost reefs even though fishermen and divers may benefit. Previous research stud-ies suggest lost reefs are utilized as de facto refugia, potentially benefiting fisheries stocks (Turpin and Bortone 2002). This manage-

196 JackSon et aL.

ment approach is well suited to environments like northwest Florida, especially the offshore LAARS that were not a part of this survey proj-ect. However, nearshore, where there are nat-ural reefs, trawling, and navigation lanes, it is prudent to manage all reef structures closely.

A number of the structures detected dur-ing the survey illustrate valuable lessons for ar-tificial reef deployment and management (a complete listing of the coordinates and struc-tures located is attached in Appendix A). One of the highlights included locating approxi-mately 30 of the 270 cast concrete artificial reef modules deployed from Okaloosa Coun-ty’s Project 100M deployment from Septem-ber 1993. The location coordinates recorded allowed the team to return to the site and find the reef material with a conventional fish finder. Locating only 30 out of 270 units origi-nally deployed is a small recovery rate, but it is known from previous diving observations that most of the modules from the 100M project were not deployed upright (Horn 1996). The modules were not designed to be self-support-ing when lying on their sides. These past dive observations also suggest many of the mod-ules have collapsed or were buried. Video ob-servations conducted during this survey con-firm modules placed upright have survived a number of major hurricanes although all are at least 50% buried and are relatively ineffec-tive as habitat.

Additionally, the team located 21 of 24 tank turrets originally deployed in May 1998. Some of the turrets are clusters, two of which were monitored by video. The observed tank turret clusters support a diverse population of reef fishes. Fourteen of the turrets were outside the boundaries of the published de-ployment coordinates, some by as much as 750 m.

An example of a well-known reef struc-ture that was not located is the pier rubble from the Okaloosa Island Pier. The material was documented by the county as being de-ployed January 1998 but apparently does not lie within the 3.9-km area scanned around the targeted deployment site. It is not clear why this is the case. Deployment coordinates could have been inaccurately recorded or the

structures were moved or buried during re-cent storms.

Some artificial reef deployments are known to have moved over time. For example, 44 liquid storage tanks were deployed south-east of Destin’s East Pass in June 1990. In 1995, Hurricane Opal scattered the tanks over a large area. Anecdotally, local divers reported finding several storage tanks prior to Hurri-cane Ivan (2004), confirming their physical integrity and fish-holding ability. This loca-tion was approximately 25 m southeast of an army turret, which was considered to be a very stable artificial reef structure (Davis and Cros-by, personal observations). However, SSS ob-servations conducted by the ECRA team after Hurricane Dennis (2005) revealed only one object large enough be a liquid storage tank (Figure 3). This location was approximately 45 m from the location noted by divers after Hurricane Ivan (2004). This implies that the unaccounted liquid storage tanks moved or were crushed and buried during subsequent hurricanes and tropical storms. Previous to the 2005 study, restrictions on materials were imposed to prevent deployment of cylindri-cal materials of this type. Currently, materials such as concrete mixer drums are inspected and modified to improve stability (Figure 4). Stability rods and openings in the drum are now required. This type of structure is only permitted in the LARRS and not in near-shore waters. Typical depths in the LARRS are 30–90 m; these deeper waters allow for fewer impacts from storm surge and wave actions to effectively increase stability as compared to nearshore, shallower sites.

It is believed that only a portion of the ca-pability of the side scan unit was used in the 2005 survey. Side scan clearly discriminates be-tween various bottom substrates. With ground truth of the associated imagery, the sonar could be used to select future reef deployment sites that are on firm sand or a thin layer of sand over natural hard bottom, thus improv-ing reef survival and longevity. The side scan also detects reef fish (Figure 5). There may be applications where the sonar can be used as a semiquantitative method for assessing the effectiveness of reef materials. With appropri-

197artificaL reef aSSeSSment uSinG SiDe Scan Sonar

Figure 4. Stability modification of cement mixer drums that have been inspected and are ready for deployment in the LARRS.

Figure 3. Low frequency image of army tank and liquid storage tank (circled).

198 JackSon et aL.

ate software, a mosaic can be constructed by combining the sonar tracks. The product, an accurate map of the reefs and surrounding area, should be very useful in relating reef de-sign and orientation to reef production. As a baseline, it is recommended that side scan im-agery be obtained prior to the deployment of artificial reefs. Once the reef is deployed, the side scan can again be used to document the physical relationship of the reef components.

In conclusion, this project demonstrated the utility of an inspired and motivated com-munity team in local artificial reef monitoring when provided with the proper training, re-sources, technology, and support. The success of this survey suggests that skilled volunteer groups can play a larger role in artificial reef management and monitoring. The capacity to execute these types of projects at the local level complements traditional research infor-mation from universities and government en-tities. These types of voluntary contributions

are of great value, building the knowledge base in the application of artificial reefs. As a result of these activities and future SSS moni-toring projects, local County artificial reef co-ordinators can make improvements in prede-ployment site evaluation, artificial reef design, and material selection based on observed per-formance in local environments. Additionally, knowledge gained regarding movement of reef materials will result in greater stability for future deployments.

AcknowledgmentsMany thanks to Bill Horn, Keith Mille,

and Jon Dodrill in FWC’s Division of Marine Fisheries Artificial Reef Program for providing technical guidance and support for local con-struction and monitoring projects. This article includes information funded by Grant Agree-ment FWC-04029. The authors also thank lo-cal reef managers and marine educators for

Figure 5. High frequency imagery of tanks turrets with a school of reef fish (circled). A school of fish on either side of the towfish may be seen a few feet north and south of the sonar track with the fish on the south side casting an acoustic shadow in the form of the letter “W”.

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contributions to this article, including Cindy Halsey with Okaloosa County, Robert Turpin with Escambia County, Craig Petermann with Bay County, and Brian Cameron with Uni-versity of Florida Sea Grant Extension in Bay County. Finally, thanks to Bill Lindberg of the University of Florida Department of Fisheries and Aquatic Sciences for providing research support required to complete many of our reef building and monitoring projects.

ReferencesBell, F. W., M. A. Bonn, and V. R. Leeworthy. 1998.

Economic impact and importance of artificial reefs in northwest Florida. Florida Depart-ment of Environmental Administration, Of-fice of Fisheries Management and Assistance Service, Tallahassee.

Horn, W. 1996. Project report for Okaloosa County

area, May 1 1996. Unpublished report. Florida Department of Environmental Protection, Arti-ficial Reef Assessment Dive Team, Tallahassee.

Horn, W. 2007. State of Florida artificial reef loca-tions (as of October 3, 2007). Florida Fish and Wildlife Commission, Division of Marine Fish-eries Management, Tallahassee.

Parsons, G. H., G. Davis, K. Crosby, and L. S. Jack-son. 2006. Historical artificial reef assessments of Okaloosa County sites 2–4 using side scan sonar, final report. University of Florida Sea Grant, Gainesville.

Florida Department of Highway Safety and Motor Vehicles. 2007. Vessel statistics by county. Flor-ida Department of Highway Safety and Motor Vehicles, Tallahassee.

Turpin, R. K., and S. A. Bortone. 2002. Pre- and post-hurricane assessment of artificial reefs: evidence for potential use as refugia in a fish-ery management strategy, ICES Journal of Ma-rine Science 59:S74–S82.

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Appendix A. Site coordinates of confirmed nearshore artificial reef sites from a 2005 survey off the coast of Destin, Florida’s East Pass. (WAAS GPS = Wide Area Augmentation System Global Poisition-ing System.)

WAAS GPS WAAS GPS Side scan Side scan Site name latitude longitude latitude longitude

A Leg Bridge Pilings 1 N30 21.816 W86 29.477 N30 21.802 W86 29.473A Leg Bridge Pilings 2 N30 21.810 W86 29.495 N30 21.794 W86 29.505A Leg Bridge Pilings 3 N30 21.805 W86 29.569 N30 21.800 W86 29.568A Leg Bridge Pilings 4 N30 21.799 W86 29.612 N30 21.797 W86 29.611A Leg Bridge Pilings 5 N30 21.791 W86 29.694 N30 21.787 W86 29.690A Leg Bridge Pilings 6 N30 21.800 W86 29.722 N30 21.798 W86 29.718A Leg Modules 1 (3) N30 21.783 W86 29.788 N30 21.782 W86 29.784A Leg Modules 2 (4) N30 21.790 W86 29.790 N30 21.795 W86 29.786A Leg Modules 3 N30 21.789 W86 29.821 N30 21.788 W86 29.817A Leg Modules 4 (2) N30 21.783 W86 29.844 N30 21.782 W86 29.842A Leg Modules 5 (2) N30 21.800 W86 29.849 N30 21.800 W86 29.849A Leg Modules 6 (2) N30 21.794 W86 29.865 N30 21.794 W86 29.863A Leg Modules 7 N30 21.787 W86 29.966 N30 21.787 W86 29.964A Leg Modules 8 N30 21.790 W86 29.983 N30 21.789 W86 29.982A Leg Modules 9 (2) N30 21.786 W86 30.024 N30 21.786 W86 30.022A Leg Modules 10 Not confirmed Not confirmed N30 21.770 W86 30.365A Leg Modules 11 (2) N30 21.761 W86 30.387 N30 21.764 W86 30.387A Leg Modules 12 N30 21.754 W86 30.384 N30 21.752 W86 30.382A Leg Modules 13 N30 21.759 W86 30.398 N30 21.761 W86 30.398A Leg Modules 14 (4) N30 21.763 W86 30.418 N30 21.757 W86 30.416A Leg Modules 15 Not confirmed Not confirmed N30 21.759 W86 30.441B Leg modules 1 N30 21.311 W86 24.433 N30 21.310 W86 24.437B Leg modules 2 N30 21.316 W86 24.495 N30 21.310 W86 24.491B Leg Modules 3 N30 21.306 W86 24.575 N30 21.309 W86 24.589B Leg Modules 4 N30 21.314 W86 24.650 N30 21.305 W86 24.658B Leg Modules 5 N30 21.306 W86 24.688 N30 21.302 W86 24.687B Leg Modules 6 N30 21.316 W86 24.828 N30 21.314 W86 24.826C Leg Modules 1 N30 21.461 W86 24.490 N30 21.461 W86 24.492C Leg Modules 2 N30 21.391 W86 24.490 N30 21.386 W86 24.483Liquid Storage Tank N30 21.339 W86 25.367 N30 21.341 W86 25.376REEFEX 8 N30 21.338 W86 25.433 N30 21.334 W86 25.426REEFEX 9 N30 21.327 W86 25.344 N30 21.331 W86 25.351Tank Turret 1 N30 19.604 W86 35.640 N30 19.610 W86 35.633Tank Turret 2 N30 19.602 W86 35.658 N30 19.605 W86 35.657Tank Turret 3 N30 19.620 W86 35.734 N30 19.620 W86 35.739Tank Turret 4 N30 19.611 W86 35.756 N30 19.614 W86 35.763Tank Turret 5(3) N30 19.555 W86 35.996 N30 19.556 W86 36.000Tank Turret 6(3) N30 19.573 W86 36.046 N30 19.572 W86 36.046Tank Turret 7 N30 19.618 W86 36.140 N30 19.620 W86 36.139Tank Turret 8 N30 19.608 W86 36.154 N30 19.606 W86 36.153Tank Turret 9(3) N30 19.625 W86 36.158 N30 19.623 W86 36.155Tank Turret 10 N30 19.626 W86 36.167 N30 19.626 W86 36.170Tank Turret 11 N30 19.618 W86 36.170 N30 19.620 W86 36.172Tank Turret 12 N30 19.627 W86 36.207 N30 19.630 W86 36.205Tank Turret 13 N30 19.646 W86 36.218 N30 19.646 W86 36.217Tank Turret 14 Not confirmed Not confirmed N30 19.630 W86 36.218Tank Turret 15 N30 19.590 W86 36.218 N30 19.590 W86 36.220