Determine if a point is over land or water

Given a point (latitude, longitude), is there a function or easy way to determine if the point is over land or over water?

I could download coastline data from NOAA and determine if a point falls inside a polygon, but I'd rather not develop an algorithm myself if it already exists.

[Mike D.]

I see that File Exchange has a function gebconetcdf that someone created, and then I discovered the code that I need:

gebconc = netcdf.open('gebco_2021_n60.0_s10.0_w-90.0_e-40.0.nc', 'NOWRITE');

XGRID = netcdf.getVar(gebconc,0);

YGRID = netcdf.getVar(gebconc,1);

BATHY = netcdf.getVar(gebconc,2);

netcdf.close(gebconc);

[KSSV]

ncread is simple to use.

Answer 1

[KSSV]

Download GEBCO bathymetry data.... https://www.gebco.net/data_and_products/gridded_bathymetry_data/

For a given lon, lat; use interp2 and get the elevation/ bathymetry value, if the value is negative it is depth and lies in the ocean or water and if the value is positive it lies in the land.

[Mike D.]

Do you have an algorithm to read the binary *.nc file into an array variable?

[KSSV]

Read about the function ncread.

[Mike D.]

The ncread function wants the variable name and I'm not sure how to extract the 2-byte integer values of elevation from the NetCDF file.

[KSSV]

Read about ncdisp. This function will give you variables from there you give the variable name.

[Mike D.]

Yes, I can see that both ncdisp and ncinfo tell me all about the structure, what I wanted was the few lines of code that allow me to read the binary file into Matlab variables.

Answer 2

[John]

There is now an API service called IsItWater.com which will let you check with a webservice call:

Request

curl 'https://isitwater-com.p.rapidapi.com/?latitude=41.9029192&longitude=-70.2652276&rapidapi-key=YOUR-X-RAPIDAPI-KEY'

Response

{

"water": true,

"latitude": 41.9029192,

"longitude": -70.2652276

}