| · It would be great to show a few more places like the Big Rock, 23 mi rock, steeples, 90 foot drop, grouper hole, swansboro hole, etc. If you would like to put me together a list of places with the lat and long I would be happy to add them.
(It takes a lot of time to look all those up and then add them. If you supply me with a premade list...all I have to do is add them....) [ Back to Top ]
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| · Why do I have to click to get the Depth? (or Temp or Clor Level) Let me tell you the Good, Bad and the Ugly about what I have online and what others do online.
There are 2 different ways of doing things online. Server Side or Client Side. I will refer to these as SS and CS. Both of these have there place online. They both do some good things and some things not so good.
CS Maps. You have seen these online. You can roll your mouse across the map and the depth and Lat and Long appear in the menu. The good thing about this is exactly what you were just talking about....getting to roll them slowly across the map and you can see the information right there...right now.
They are made using JavaScript. You take a picture and geo-reference it. Say the top left corner is this X Lat and Y long....the top right is X and Y.....the bottom left is X and Y and the bottom right is X and Y. The script (program) figures out the distance (in pixels) between top left and top right and what the corresponding lat and long would be for each pixel along the way. This is what gives you the Lat and Long as you roll the mouse. (The rolling display of Lat and Long that I use works about the same way) Depth…..They take the same image (It is just a picture) and assign values to the various colors. To keep this simple we will call them all different colors where is reality they are usually various shades of blue. What you do is say Blue = 100 ft, Green = 101, Yellow = 102, red = 103 and so on. (remember we are calling them different colors when they are really various shades of blue) as you move across the map with the mouse the computer figures out what color it is passing over the top of and displays the corresponding value that is written into the script. Here is where this gets interesting. The problem with doing things CS is inaccuracies. Because the image is geo referenced in pixels the lat and long lie. Because the values are assigned to a color....you get the value of the color....not the value of the depth. ( kind of like making a copy of a copy)
The reason I know all about this is I looked long and hard at doing my maps this way. (When I started this I really really wanted to do it this way) We even made one as a trial to see how well we could make it work with the data we are using. The data itself is pretty accurate and the resulting map that we made just could not display the accuracy that the data source had.
So we switched and went to SS.
The maps you get here are all generated SS. (With the exception of the rolling Lat and long, Always click to get an accurate Lat and Long for a feature on my maps) When you look at my maps you are looking at colored data. (The colors are assigned to the data, not the data assigned to the colors) Let me give you an example. Since you were interested in depths lets talk about the Coastal Relief Model. (this is a little oversimplified to make it easier to understand) The model itself is nothing more than a excel table with 3 cells. Lat, Long, Depth. That’s it. When we display a map for you we pull the extent (Lat and Long at the corners) we query the database for the Lat, Long, Depth in-between the corners. Then we assign colors to the values. It is those values that you are seeing on the map that have had a color assigned to them. This is the major difference between how things are done between SS and CS. In CS you assign the value to the color, in SS we assign color to the value. This is so that we do not pollute the values. The bad part of that is that we can not display the values with out going back to the database to get the value. That is why you have to click on the map. It is going back to the database and getting the value assigned to X lat and Y long. (the real X and the Real Y not the one displayed in the rolling Lat and Long) What you get here is as accurate as the data being used. In our case we are using the Coastal Relief Model which is science grade data that is as accurate as there exists in the world today. There is not a map, there is not a program there is not a way of doing it that is any more accurate than what we are doing right here. The big draw back is you have to click to get the data.
The SST's and other maps we have here are the same way. They are not "Pretty Pictures" as they are called in the mapping trade. They are all colorized data. I spent a GREAT deal of CASH to make sure that everything we have done here is as accurate as possible.
I will give you an example. Sitting beside of me is a testing server. I dumped my entire GPS onto the depth map. I was SHOCKED at how close it really was to what the map showed color wise. Where it showed the change in color.....there was my number.
If I wrote software for computers, (I would have no clue) what I have right now could do everything SEEBottom used to do plus some. To try to do it online would not work because of the limitations in bandwidth and those limitations inherent to the internet.
If I recall the model is 3000 data points by 3000 data points per square mile. How long do you think that would be to download a map of NC and SC. Then put 10 users trying to do the same thing all at once....grid lock. (This could be done with JavaScript as well but the download times and server load keep us from even trying)
I hope that helped. Sorry you have to click to get the value. That is just the way it works.
I wish everyone would tell me what they want out of these maps so I can try to make them better. Some things I can do something about and some things I cannot.
Dave
(I am going to add this to the FAQ section for future reference)
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