Using A Nautical Chart For Bottom Relating Kings

[GLF]

Everyone knows what a Nautical Chart is....correct? For those that dont,

A nautical chart is a graphic representation of a maritime area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land, natural features of the seabed, details of the coastline, navigational hazards, locations of natural and man-made aids to navigation, information on tides and currents, local details of the Earth's magnetic field, and man-made structures such as harbors, buildings and bridges. Nautical charts are essential tools for marine navigation; many countries require vessels, especially commercial ships, to carry them. Nautical charting may take the form of charts printed on paper or computerized electronic navigational charts.

Nautical Charts are lacking deeper depth line contours. It is hard to distinguish underwater structure without these lines. Most kings are nomads, but by knowing where the underwater structure is, you may increase your catch when kings are relating to the bottom. Once you have your Nautical Chart mapped out, you can plug the latitude and longitude coordinates into your gps and fish these structures. Fish may be relating to the structure in a certain direction. You may have to make multiple passes over the structure in multiple directions to pick up fish that are relating to the structure. If you do not believe salmon relate to structure, would someone tell me why at certain times of the year salmon will be caught on the rims of some of the holes(bowls), or humps though out the lakes?

If you are trolling along and pick up a fish off the bottom, mark the spot on your GPS. There may be a reason that fish was there. After you get home, check your way point coordinates to your Nautical Chart and see if there is structure the fish was relating to.

How many times have you been trolling along and came across a bait ball sitting on the bottom? Bait fish will also relate to structure. Structure on the bottom can be anything. It can be a drop off, hump, point, rock, sunken boat, weed, or any other bottom abnormality. Where there is bait, you will find fish.

Here is what a section of a Nautical Chart looks like without the depth lines added.

For those that want to add lines to your charts, here is how.

The more detail of your Nautical Chart, the more structure you will see. There is no pattern of numbers for the depths on the chart, so I will pick a depth and start with that. You will want to drawn your line between the depths where it fits on the chart. I selected 50' for the first line I added. I drew the lines on these images with my mouse, so excuse them if they are a little shaky.

50' Line

Do you see the big flat just North of Ludington, and the sharp inside bend on the South side of the flat?

I added a 60' line to the next drawing. Note:See the little point between the two 60' marks? The number to the left of it looks like a 51 or 61. I am calling it a 61, which is why the depth line goes to the inside of it.

60' Line added

Do you see how sharp the little point is?

I added a 70' line next.

70' Line added

The 70' line does not show a lot of structure. Everything has a gradual bend.

I added a 80' line next.

80' Line added

Notice the top half, how close the depth lines are together. This is a sharp drop off.

I added a 90' line next.

90' Line added

See the sharp underwater point and the inside bends?

I added a 100' line next.

100' Line added

The 90' point extends deeper and there is a sharp drop off on the inside bend at 102' just North of it.

Now that you have your depth lines drawn, you can take the gps coordinates of these structures from the Nautical Chart and plug them into your gps. The next time you are out fishing and see fishing relating to bottom, see if there is a reason why they are at that certain location.

Mike Heckman(GLF)

www.greatlakesfisherman.com

[Valinote]

Well done, Mike. Nice article! Do you know if there's any place that sells bathymetic maps with the depth contour lines already plotted? A soft copy that runs on your PC would be even better, especially if the lat/log was active via your mouse pointer!

-Steve D

[GLF]

Well done, Mike. Nice article! Do you know if there's any place that sells bathymetic maps with the depth contour lines already plotted? A soft copy that runs on your PC would be even better, especially if the lat/log was active via your mouse pointer!

-Steve D

Thanks Steve! Welcome to Great Lakes Fisherman. I am sure there is software out there that does exactly what you are talking about. Unfortunately I have never played with it, nor seen it.

One thing I left out that I probably should have mentioned. Everyone fishes the thermocline when it developes. Now follow the depth of the thermocline to where it intersects with a piece of bottom structure. This is a place that may hold a school of bait fish.

[GLF]

I will be coming out with a part two for this that shows how to use some software that I found. This software is available on the web for FREE and gives you depth contours and GPS cordinates.

[Priority1]

I would be very interested in that. Isn't the WWW GR8.

[GLF]

My photoshop skills are not up to par. This is why I have not came out with the part 2 yet. It is actually a site and not software.

http://map.ngdc.noaa.gov/website/mgg/greatlakesbathy/viewer.htm

If you can not get that link to work, try this one.

http://map.ngdc.noaa.gov/website/mgg

Once you get that loaded, click on "greatlakesbathy".

I will give everyone a brief run down.

I am going to use Lake Michigan for my run down.

1. On the right side of the screen, put a check in the square box next to Lake Michigan Bathymety.
   
2. Uncheck the squares next to Lake Erie Coast Line, Lake Huron Coastline, and Lake Ontario Coast line.
   
3. You should now only have 3 squares checked. Click on the "Refresh Map Now" button at the bottom right.
   
4. This should put depth contour lines in Lake Michigan. Click on the magnifying glass with the "+" in it. This is the zoom in feature. Click where you wish to zoom in on the lake. For this demo I am going to click on Grand Haven. For those that do not know where Grand Haven is, its the longest river on the right side of the lake about 1/3 of the way up from the bottom.
   
5. I click once and it now shows 0 to 90mi. on the scale at the bottom. Do you see the underwater point between Grand Haven and Holland. I am looking at the point on the 4th contour line out. I am not sure of the exact depth of this, because the contour lines do not have depths.
   
6. Click on that point. Your scale should now show 0 to 46mi. Click on the point again. Your scale should be at 0 to 23 miles. Notice you have more depth contour lines now. Port Sheldon is the tiny spot below Grand haven and Holland is below that. The point is actually between Port Sheldon and Holland. I am looking at the point that is on the 3rd depth contour out from the dark depth contour line.
   
7. From here its just a matter of zooming in to the scale you wish to use. The smaller the scale, the more accurate the cordinates will be.
   
8. Looking at the bottom of my display, I have a blue bar that goes accross it. In the blue bar on the left side, it says "Zoom In" in the middle "About Database" and right "Help"
   
9. Below this bar I have a white bar. In this white bar it starts with an internet explorer icon then "Map" and a bunch of numbers. These numbers are the cordinates of where you pointer is.
   
10. I have my pointer on the tip of the point, and this is what is shown in the white bar.
    

e Map:-86.56 , 42.82 -- Image:511 , 331 -- ScaleFactor:0.002159309021113244

These are the GPS cordinates of this point. -86.56.511 , 42.82.331

Enter these into your GPS unit and it should get you pretty close to where you are wanting to get to. As they always say. DO NOT USE THIS AS A NAVIGATION AIDE. I am not sure why they say that other than to cover there butt incase there is an error and someone has an accident.

Click on the ruler on the left side of the screen with a "?" above it. Its 4 buttons below the magnifying glass. Now left click on Port Sheldon and release the button. Now you can move the pointer anywhere on the screen and it will give you the distance to that your pointer from Port Sheldon. I have the pointer on the tip of the point and I am showing 19 Miles. This is shown in the white box on the top left of the image.

If you wish to have a different starting point, you have to click on the eraser image(Clear Selection), then click on the ruler again.

To do Lake Huron, Erie, or Ontario, just repeat the steps from the top except select the lake you wish to view.

Any questions?

If you are having problems, send me a PM and I will tell you how to get ahold of me.

Mike

[LongLine]

GLF

Thanx. That's a neat site. Just did some Feature IDs on Lk Ontario. (the "i" in the black dot icon). The dark contour lines are 10 meter depths. Between shore & 10 meters each represents 1 meter. Between 10 & 20 meters, they show 12, 14, 15, 16, & 18 meter. Beyond that they're 2 meter each.

Tom B.

(LongLine)

[GLF]

GLF

Thanx. That's a neat site. Just did some Feature IDs on Lk Ontario. (the "i" in the black dot icon). The dark contour lines are 10 meter depths. Between shore & 10 meters each represents 1 meter. Between 10 & 20 meters, they show 12, 14, 15, 16, & 18 meter. Beyond that they're 2 meter each.

Tom B.

(LongLine)

Thanks Tom!

I think the contour lines will vary in depth depending on how far you are zoomed in. I still need to play with it some more to get a better understanding.

[GLF]

Here is another online map program that will give you GPS cordinates.

Mapserver

Zoom in on the area you wish to find your coordinates. Where you point your mouse is your Latitude and Longitude.

[Joe von Grabe]

The bathemetry site is very interesting with good information.

The L&L coordinates don't come up on my computer at work. Any ideas?

They come up on computer at home but I found they are totally inaccurate and useless. Are you finding the same thing?

Joe