Bathymetry and grid for a small lake

Discussion of how to use ROMS on different regional and basin scale applications.

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OlgaVolodko
Posts: 1
Joined: Wed Apr 06, 2016 4:36 pm
Location: Immanuel Kant Baltic Federal University

Bathymetry and grid for a small lake

#1 Post by OlgaVolodko » Sun Jun 05, 2016 6:32 am

Dear all,
We have recently started to work with ROMS and the subject of our interest is the Lake Shira (Khakassia, Russia).
Now we have the problem with export bathymetry of the lake.
We tried to use Coastline Extractor, but the Lake Shira is not marked on the map.

We have bathymetry of Lake Shira as the set of irregular points: longitude, latitude, depth.
Coastline is not defined. Array of points is not a rectangle.

Now,we try to use the Matlab programs (exractor_bath.m and others), but not shure it's correct.

What steps we need to do to get grid.nc file for transfer it to the initialization file ocean.in?

kekejiayu
Posts: 6
Joined: Tue Mar 01, 2016 1:38 am
Location: Nanjing University

Re: Bathymetry and grid for a small lake

#2 Post by kekejiayu » Wed Sep 07, 2016 2:08 pm

Hello,I have The same problem and I want to konw have you solve this problem .
Ps. my study area is a small lake in Hainan ,China .

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shchepet
Posts: 185
Joined: Fri Nov 14, 2003 4:57 pm

Re: Bathymetry and grid for a small lake

#3 Post by shchepet » Sat Sep 10, 2016 6:02 am

I tried to build grid for lake Shira using the latest available GSHHS version 2.3.6
shoreline data set taken at full resolution, gshhs_f.b, see
https://www.soest.hawaii.edu/pwessel/gshhg/
and this is what I managed to get:
Image
The lake exists in this data set, however its contour is not
accurate, if compared with satellite image from NOAA,
Image
even thought I was able to get accurate images of some other lakes and rivers in the surrounding.

This puzzles me: Both Google Maps and Google Earth give consistent
and, I believe, correct shape, same as NOAA, but according to the web
suite of GSHHS, all these maps (including ESRI) are based on the same
data.

Furthermore, GSHHS web suite says that it is a merged product using three
data sets, of which CIA World Data Bank II (WDBII) is the source for lakes
and political boundaries, while there is an additional data set for rivers.
Upon getting and examining WDBII I found that there is no contour in the
vicinity of coordinates where Lake Shira should be.

Obviously the lake is too small, very far away from where most modeling occurs,
and not merely roundoff-error of GSHHS restricts its resolution to 10^(-6) of degree,
that is about 100 meters north-south and 50 meters east-west, which however still
should be able to capture its shape accurately. Years of experience with building
grids and masks using GSHHS alone, see
viewtopic.php?f=23&t=3878
makes it into a kind of all-what-you-need category for ROMS modeling.
Yet am I missing anything? Does anybody on this forum know about a more modern
version of WDBII than the one from year 2000 which is pointed by the link from
GSHHS web suite?

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