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Mapping and Physical Data Procedures

The main products of the Map Team are site maps, physical data reports for each dive on the site, and placement and maintenance of ID markers at specific locations on the site for use by other specialists. Tasks consist of reconnaissance surveys of a site and its surroundings, measuring physical dimensions of sites, creating, placing and maintaining markers for ID stations, GPS measurement of landmarks on the sites, pathfinding for navigationally challenged ID specialists, and collecting and inputting physical data for each dive. Mapping is generally done with two or three person teams.

The following section provides the procedural approach to be used for the various tasks of the Mapping specialty.

Site Maps:

On new unmapped sites, the mapping leader and mapping team members will perform a reconnaissance dive on the first team dive to the sites. They will do an overall sketch of the site, identifying prominent features that would be easily found by other dive team members on subsequent dives to the site. They will also observe where fish tend to aggregate, as potential locations of fish ID stations. Once benchmarks are installed (see below), the mapping team members will begin to map the site with the tape measures, compasses, depth gauges, and GPS. The relationship of the benchmarks to one another will be established by both distance and bearing (azimuth readings), and other portions of the reef will be mapped in relation to the benchmark locations.

Once a site has an established base map, further refinements are prepared to determine if storms have caused shifting of the reef material, or in the case of wrecks, deterioration of the reef material has caused shifting and/or profile changes. Cross sections of the reef profile through the benchmarks in both a north-south and east-west direction may be prepared using depth gauges along the transects.

The output product of this exercise will be a 11 x 14" (legal size) laminated map of the site for use by the team on subsequent dives. Revisions to the map will be made as new areas are explored or added by ERM.

Physical Dimension Measurement:

Mappers will measure the distance between two points underwater by reading the numbers from the reel-type tape measure they stretch between the points, and my taking the compass heading the tape makes when tight. Generally, two members should start at the same position, with one remaining in place to hold the tag end of the tape while the other plays out the tape from the reel as he/she moves to the point to be measured. When there, the tape is stretched tight and the measurement written on the slate. They will each sight along the tape measure when it is stretched taut between the two points and obtain an azimuth bearing on their individual compasses. Their readings should be 180 degrees apart, and within 5-10 degrees of being the reciprocal of their partner's reading. The average of these two readings is taken as the measurement. Measurements are made from benchmarks to other features on the site. On larger area sites, mapping measurements generally begin at a benchmark and continue in one direction utilizing multiple measurements as limited by the tape measure length, visibility, and currents.

In strong currents, where measurements must be made perpendicular to the direction of the current, it is highly recommended that a three person team be utilized, with the third diver helping to hold the tape in the middle of the distance between the two features being mapped. This will help take the bow out of the tape caused by the current.

Mapping team members should establish command signals with their partner concerning when measurements are to be taken, when finished, and when ready to move to new location.

At the end of the dive, all mapping team members should get their mapping information to the mapping team leader immediately after the dive or if he is not present on the dive, by a timely email message.

Physical Condition of Wreck Structures:

On dives where ships are being utilized as artificial reefs, a physical inspection of all the structures involved will be conducted, and the results included in the written report. Where feasible, wide angle photographic evidence shall be taken to establish a chronological record of the wreck's deterioration over time.

GPS Measurements:

GPS measurements of major landmarks on the dive sites are obtained using GPS equipment floating on the surface and towed by a diver. This system was devised by a PBCRRT member and is in use in over a dozen locations throughout the world.

It consists of a small handheld GPS instrument sealed in a clear container strapped to a dive flag buoy, that is towed by the mapping team diver using a reel of measured line. The GPS is set to record positional tracks at regular intervals in time. The diver can then locate a benchmark or prominent feature underwater and tie off to that feature for a minute or two. Time of day is noted for each feature measured and used to find the surface location of the GPS at that time (done after the dive is completed and the GPS record dumped to a computer). The length of line to the flag, the site depth, and the compass bearing the flag line makes with respect to north is also recorded, and used to correct the surface location of the GPS to the exact underwater site location. This process has proved to be accurate and as reliable as if the underwater site was on the surface.

Complete details for building and operating this system can be found on WadesPage.com

Physical Data:

The following physical data shall be recorded for each dive on each site:

  • wind speed, direction from which it is coming, nature of the weather and the sea state.
  • current speed and direction toward which it is flowing
  • water temperature and horizontal underwater visibility at two levels in the water column
  • dive start and end times
  • general notes on the conduct of the dive

The physical data is collected utilizing the following methods:

  • thermometers for water and air temperature
  • NOAA weather reports or the diver's senses for wind speed and direction,
    wave heights, and general weather conditions
  • the drifting GPS or diver's estimates for current speed and direction
  • listen to the team pre dive briefing to learn the specifics of his/her assignment for the first dive

Tape measures will be used with Secchi disks or white diver slates to measure underwater water visibility. A tape measure is played out until the Secchi disk or a diver's slate is no longer visible by the diver with the reel end of tape. The distance is then recorded as visibility. These measurements should be taken near the surface (within 15 feet of surface) and a few feet off the bottom of the dive site on the reef.

Once collected, the data is to be entered into the database using the online data entry form, which automatically produces an online and printable report page for use in the report cycle.

ID Marker Placement:

In collaboration with the Fish Leader, Invertebrate Leader, and Science Coordinator, the Map Team will determine locations for fish surveys and invertebrate monitoring on a site. They will construct permanent plastic markers containing contrasting alphanumeric lettering to be used to identify specific locations as fish ID stations or for invertebrate photo surveying points of interest. These markers will be affixed to concrete blocks or steel stakes brought to the site, or attached directly to limestone rock or concrete rubble already on the site.

On subsequent visits to the site, the map team will locate all markers, clean them of overgrowth, replace the ones noted as missing from previous dives, and note the ones that need to be replaced in the future.

Photo and Video Techniques for Map development:



Mapper Certification Requirements:

Mapping is the most task loaded of the specialties, requiring an ability to cope with upcurrent swims, poor visibility, and hands full of equipment. It also requires experience in navigating the various sites the Team dives, which can only be obtained over time by actually diving the sites. To be obtain the Mapping Speciality Certification:

  • Complete the Research Diver Orientation Class
  • Learn to use the GPS system
  • Participate in a mapping activity on at least 10 different dive sites under the tutelage of a certified mapper.