Water Depths and Rigs south of Last Islands
~ Captain Paul's response to: ~ K. Robichaux ~
To cover the areas you mentioned, you should look into getting two Official NOAA Marine Charts.
Chart # 1116 covers the LEASED BLOCKS from the Mississippi River to Galveston, Tx. It is in a scale of 1:458,596 and indicates the positions of the offshore (Federal) Leased Areas and their respective Leased Blocks. This chart shows platform and underwater pipeline locations as well as the water depth in FATHOMS. One fathom equals six feet, so fifty feet of water is about 8.33 fathoms and seventy-five feet depth is 12.5 fathoms.
As stated the scale ratio is quite large which is needed to cover that large of an area on one chart, so remember that when setting your courses and plotting platform positions that they will not be as accurate as those plotted on a larger scale (smaller ratio) chart.
To supplement this chart you should also obtain NOAA Chart 11356, Isles Dernieres to Point Au Fer. This chart is in a scale of 1:80,000 which is the standard for normal coastal charts. It indicates the water depths in feet.
The reason for the two charts is that chart 11356 only covers a distance of about 33 miles south of Racoon Point, which is not yet in the 75 foot depth you asked to cover. No, I did not mis-spell Racoon Point, that is how all of the official charts and maps indicate its name.
Chart 1116, Leased Blocks. . . covers from the shoreline out to about the Walker Ridge area in 1000 fathoms, which is about 160 miles from the shoreline.
Both charts are configured using WGS 84 Datum, so do your plotting using that value.
These NOAA charts can usually be purchased at any marine supply company or at an authorized NOAA Chart dealer. The NOAA web site lists their contractors for selling such charts in your area.
For the distance part of your question, from Racoon Point the 50 foot depths are shown on the charts to be about 28° 39.918’ N. Latitude ~ 90° 58.250’~ W. Longitude and the 75 foot depth are found about 7.8 miles farther south at or 27.5 miles due south of Racoon Point at or about 28° 33.254’ N. Latitude ~ 90° 58.250’ W. Longitude for a total of about 35.3 miles.
The charts indicate that after a vessel would pass over the underwater ridge named SHIP SHOAL, the bottom begins a gradual deepening out to 2000+ fathoms.
The charts also indicate that there are some but not many platforms between the 50 foot and the 75 foot depths in the area south of Ship Shoal, but not nearly as many as there are around the +75 foot depths. This area, just a 3 to 4 miles farther south at or about 28° 29.942’ N. Latitude ~ 90° 58.250’ W. Longitude, contains an almost uncountable amount of platforms. This area in the SHIP SHOAL AREA, blocks 219 to 235 alone contain over 30 platforms. These platforms are in about 100 feet of water.
A round trip from Racoon Point would be roughly about 80 miles. That is without bouncing from platform to platform trying to find the fish. Remember that is from Racoon Point, not the launch area.
Unless otherwise specified, all positions are stated as Degrees, minutes and thousandths of minutes (DDD,MM.mmm) and were determined using WGS 84 Datum. All bearings and courses are stated in Magnetic degrees.
~ Captain Paul ~