How can I get the sea ice concentration data corresponding to the latitude and longitude from the geotiff file?

Hello，

I got daily sea ice concentration data from https://nsidc.org/data/G02135/versions/3（please see attachment）, but the file is in geotiff format, and I don’t know about geotiff format. I don't know how to get sea ice concentration data corresponding to longitude and latitude from geotiff?

Hope to get your help! Thank you very much!

Bei.

Answer 1

[KSSV]

filename = 'N_20180101_concentration_v3.0.tif' ;

[A,R] = readgeoraster(filename) ;  % If not try geotiffread

[m,n] = size(A) ; 
x = linspace(R.XWorldLimits(1),R.XIntrinsicLimits(2),n) ; 
y = linspace(R.YWorldLimits(1),R.YIntrinsicLimits(2),m) ; 

[X,Y] = meshgrid(x,y) ; 

figure(1)
mapshow(A,R)
figure(2)
pcolor(X,Y,A);
shading interp ;

[Bei JIANG]

Thank you very much for your reply. But what I want to get in the end is the numerical value, not the picture. How do I get the specific value of the longitude and latitude of each grid and the corresponding sea ice concentration?

[KSSV]

Al;ready you have those in hand.......the variables X, Y, A are the one you want.

[Bei JIANG]

Sorry to disturb you again, how can I convert the x and y you gave into lat (range 90~-90) and lon (range 180~-180)? Hope to get your help! Thank you very much!

[KSSV]

You need to know in which projection these coordinates are and then convert them or if you know the regions lat and lon, change the limits used in linspace and proceed.

[Bei JIANG]

Now I know the projection is “NSIDC Polar Stereographic Projection", and I also know this link provided transformations to geographic coordinates from map coordinates: polar stereographic coordinate transformation (map to lat/lon) - File Exchange - MATLAB Central (mathworks.cn)

However, I dont konw if the X,Y in this command （below） is the XY you provided me in [X,Y] = meshgrid(x,y)?[LAT,LON]=POLARSTEREO_INV(X,Y,EARTHRADIUS,ECCENTRICITY,LAT_TRUE,LON_POSY)

I look forward to hearing from you very much, it is very important to me. Thank you very much !

[Bei JIANG]

There are two lines wrong in your answer, corrected as follows ：

filename = 'N_20180101_concentration_v3.0.tif' ;

[A,R] = readgeoraster(filename) ; % If not try geotiffread

[m,n] = size(A) ;

x = linspace(R.XWorldLimits(1),R.XWorldLimits(2),n) ;

y = linspace(R.YWorldLimits(1),R.YWorldLimits(2),m) ;

[X,Y] = meshgrid(x,y) ;

figure(1)

mapshow(A,R)

figure(2)

pcolor(X,Y,A);

shading interp ;