How to create a map using land and depth

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Re: How to create a map using land and depth

Postby ron » Thu Jan 13, 2011 7:24 pm

Sure I can, where did I get the data? (Geodas)!
(Your Google search should always include bathy when looking for depth data?)

http://www.ngdc.noaa.gov/mgg/gdas/gd_designagrid.html
In the grid database choose Great lakes bathymetry.
edit:
Save as ascii to open these in Microdem (merge dems, as you have to cut your selection to 8000 columns/rows max).

Next, Lake Superior, when sailing on it has a geographic height of the eye of 179 meters? A hill that is 279 meters high in DEM, on a height of the eye of 179 meters will have the aspect of 100 meters, right?
So when we deduct 179 meters from the land data, the aspect on height of the eye is still 100 meters when we are at level 0.
That is what we do, (deduct 179) so we can get it in VSF/VS scenery (in the sim we are sailing at level 0, we know in reality this is +179, this case, Lake Superior).

With your question you take this tutor to a next level, away from "sea" to "lake"?

The Lake Superior data is large but only took seconds to manipulate on my PC? (and it is an old banger). If you are looking at minutes rather then seconds there is something seriously wrong with your platform.
Cheers,

Ron
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Re: How to create a map using land and depth

Postby Hrive » Fri Jan 14, 2011 4:55 pm

Thank you for the data. I had found that site, but I didn't realize that ASCII text is a .dem file, as well, so I didn't realize I could use any of it in VSF. All the formats are confusing to the novice. :?
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Re: How to create a map using land and depth

Postby ron » Fri Jan 14, 2011 7:30 pm

Hey Hrive, that's why we are here sharing experiences as we go along. This sim is as much part of Ilan (the developer) as it is part of us (the user), it is a very close and interactive relationship? At least that's my experience.
I'm Ron, ......Hrive is there a name behind your alias?
"Novice" is common, we all started that way (and that could go back to donkeys years ago). If you are not sure, just ask okay?
I'm just chuffed that you are looking into creating your own envirnment to sail the hundreds of current boats available.
Just holler if you're stuck somewhere, mind you, I'm talking the map, not the objects (unless they are navaids).
Cheers,

Ron
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Re: How to create a map using land and depth

Postby ron » Sat Jan 15, 2011 6:08 pm

Hi, since you have an issue with Landserf I have had a hard look at the data you can get from the site I listed above. In fact you don't need any bathy data, it is already there. Furthermore you can avoid using Landserf, everything can be done in MicroDEM.
Load the lake Superior data in 2 sessions (because of the max columns download restriction).
From the (2) zipfiles you have obtained extract the .asc files.
Open them (load multiple DEM) in Microdem. Since we know the height of the eye when on the lake is 179 meters, we reduce the whole loaded file(s) with 179 meters in: Edit/Single grid arithmatic/raise lower z values/
In the dialog box enter the value of -179, that's it. MicroDEM will save into a format which 3DEM accepts, I used GeoTiff.
The file loads fine in 3DEM and I select the area we are after by pressing F8, just draw a box and press enter.
Save the resulting file as a binary signed integer. Edit the resulting .hdr file to set minimum depth at 5 (this is a VSF requirement).
Copy paste both .bin and .hdr in a scenery file Lake_Superior, you're done in minutes.
Cheers,

Ron
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Re: How to create a map using land and depth

Postby Hrive » Sat Jan 15, 2011 8:50 pm

Thanks, Ron! I'm Royce, by the way. Your last post anticipated my next questions. My problem was that the program was generating its own depth information whether I lowered everything by 179m or not. I'm sure editing the header like you say will fix that. Thanks for all the help!
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Re: How to create a map using land and depth

Postby itsme » Mon Jan 31, 2011 1:22 pm

Hi Ron,

sorry to bother you. Following your tutorial I got a good scenery for Ascension Island with good depth only when I change the minimum elevation in the hdr file to 5, as suggested. However the coastline is then vertically cut.

Image

When I change the value to any other figure in the hdr file then I get a nice coastline but loose the depth to the default 276 maximum. (The original value is -5000 or so). I am sure you know the answer. I would be grateful if you could have a look at this issue. The bin and hdr files are in the following zip. ---> http://h1.ripway.com/rbauer/Ascension.rar

Thanks in advance,

Reino.
Cheers, Reino.
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Re: How to create a map using land and depth

Postby Bromstarzan » Wed Feb 09, 2011 10:33 pm

Hi Ron,
just wanted to say how much I appreciated your tutorial on merging bathymetry with land elevations.
Worked flawlessly from the first try. Although I have some issues at some shallow points, but that is just because of the data itself.
Perhaps I can make a better handmade land/water boundary intersection with time (that's what we have harbours for ofcourse :D )

As a first example I did the entire Straight of Magellan (rather continued on an old project) and it turned out a lot better now with the "real" depth info.

Image
I havn't uploaded it yet for two reasons:
1) I am not sure what scenery quality the community expects. Since there are no harbours yet, many would just waste their time, unless they just want to navigate the strait.
2) I do intend to place some navaids, landmarks and try to build Punta Arenas for example - eventually. So perhaps better to wait before putting MB on the library server. If anybody still want the package as is now, giv me a shout, I can host it temporarily on my own ftp. Perhaps we can work together to make it better for everyones enjoyment.

I like to explore the possibilities in VSF and learn how to go about realizing them. As well as enjoying all the fantastic 3D models popping up.

Cheers all,
Broms

PS: As you can see (above image) I also have the "Cape Horn" area ready to go, but that is another story.
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