Page 582 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

• Previous searches within the (or other inter-agency) department
• Fishing maps
• Archeological data from local universities
Data can be obtained from any number of other sources. A competent and effective PSD will spend time locating/gathering these items of information before being faced with a time-sensitive search. Examples of the types of data acquired during two prior searches, one an archeological search and the other a murder victim search, follow.
21.3.4.1.1 Archeological search
A good example of research was during a prior job cataloging the WW2 wreck sites of torpedoed tankers in the Gulf of Mexico in support of an effort with a Southern Louisiana university. Specific steps, information gathered, and issues encountered follow:
1. Petitioned and received the then-named Defense Mapping Agency (DMA) for non-submarine contacts within their database
2. Received from the US Coast Guard’s (USCG) 8th District, all submerged obstructions within their database
3. Received from the National Oceanic Survey (NOS) their database of wrecks
4. Received from Texas A&M University their “hangs” listing of all reported fishing net hangs
within the geographical area in question
5. Received from the US Minerals Management Services its archeological database of historically
significant items
6. Obtained copies of pipeline survey maps that displayed high-accuracy pipeline coordinates for
positional referencing
The data was not ready for populating the GIS, since all of the databases were in different coor-
dinate systems:
1. The MMS database had all information in survey block coordinates based upon North American Datum 1927 (NAD27) survey State Plane Coordinate System (since that is what the offshore oilfield leases were drawn with in the 1960s) in x, y coordinates from the reference datum point.
2. The USCG, NOS, and DMA coordinates were all in World Geodetic System 1984 (WGS84, which is the current coordinate system used by most charting systems), but the reported coordinates were sometimes as much as 70 years old, taken via dead reckoning and celestial sightings. A “reliability quotient” had to be assigned to the positioning coordinates.
3. The Texas A&M “hangs” listing was in Loran A “TDs” (i.e., timing differences), which required conversion to latitude/longitude coordinates before processing.
4. The pipeline survey maps were all in NAD27. The pipeline maps had to be merged with the production platform coordinates to accurately plot the subsea pipeline track away from the production platform. The map drawings had “shot points” where high-accuracy position readings were taken along the length of the pipeline at measured points; the remainder of the string was “connect the dots” type of dead reckoning. Therefore, all of the coordinates had to merge to the pipeline map, so they all needed to be converted to the NAD27 coordinate system.
21.3 Public safety diving 581