Can I make a shapefile out of three variables?

Hi there,

I am working on a system, where the bathymetry does not exist in Ocean Data View. I have the bathymetry data, but I would need to turn them into a shapefile to then use it in ODV.

How can I make a shapefile out of a set of coordinates (lat, lon) and depth? I have about 400,000 data points..

Thanks for your help!

Louise

[Jan]

What is a shapefile? How are the data stored and what is the wanted output format? Note that most of the forum members do not work in your field of science. But for Matlab this does not matter, because the data are numbers and the files consist of characters or bytes only.

[KSSV]

Your points make a curve or a grid?

[Louise Delaigue]

Hello! My field of science is oceanography. I would like to basically map the bathymetry that I have into a shapefile contours, to then import it into another software. I am a beginner on matlab, thanks for your patience.

[Chad Greene]

Louise, my experience with ODV is limited--what can you do in ODV that can't be done in Matlab?

Answer 1

[KSSV]

Read about shapewrite

[Chad Greene]

KSSV is referring to the Mapping Toolbox function shapewrite, if you have a license.

[Louise Delaigue]

Hey! I have been trying to get the shapewrite file to work all day but it does not seem to be creating the contours properly. I am wondering if I am getting the geometry right.

What would you guys recommend using?

Thanks!

[Sean de Wolski]

Did you look at the examples in shapewrite doc? What is the exact error that you are getting?

[Chad Greene]

Sean, the shapewrite documentation is sorely lacking any examples of how to write a shapefile from scratch. There's only one example, and it starts by assuming users already have a shapefile, but want to create a modified version of it.

[KSSV]

YOu have to proceed something like this:

% take some arbitrary data
[X,Y,H] = peaks(100) ;
[c,h] = contour(X,Y,H) ;  % get the contours

Lon = c(1,:) ;   % longitude 
Lat = c(2,:) ;   % latitude 
Data = struct([]) ;  % initilaize structure 
for i = 1:length(Lon)
    Data(i).Geometry = 'Point' ; 
    Data(i).Lat=Lat(i)  ;  % latitude 
    Data(i).Lon =Lon(i) ;  % longitude 
    Data(i).bathymetry = interp2(X,Y,H,Lon(i),Lat(i)) ;   % bathymetry
end
shapewrite(Data, 'myfile.shp')  % write into shape file 
S = shaperead('myfile.shp')    % read the shape file

[CamboSlice]

Hello,

I was wondering if this was possible WITHOUT running it through a for loop? I make MANY shapefiles and have recently been writing them using MATLAB but they take FOREVER when they contain around 10,000 points. It takes less than 5 seconds to actually compute the data but then about an hour writing it to a shapefile. Avoiding a for loop would be wonderful.

Thank you!

[Walter Roberson]

cell2struct() to avoid the loop. Probably in connection with num2cell() to create the data as cell.