Area (and voume) of interpolated scattered data

Hello,

I'd like to calculate the Area (and volume) of interpolated, scattered data. I have Lat/ Long coordinates for different altitudes. My code is as follows:

    % Read data
    clear all; close all;
    Input = xlsread('Data Input Neu.xlsx','A:C');
    Lat = Input(:,1);
    Lon = Input(:,2);
    Alt = Input(:,3);
    % Interpolation for scattered data
    F = TriScatteredInterp(Lon,Lat,Alt,'natural');
    MinLat = min(Lat);
    MaxLat = max(Lat);
    MinLon = min(Lon);
    MaxLon = max(Lon);
    % Construct meshgrid
    [X,Y] = meshgrid(MinLon:0.001:MaxLon,MinLat:0.001:MaxLat);
    Z=F(X,Y);
    % Specify z-levels
    v = [910 910];
    % Specify matrix for z-levels
    C = contour(X,Y,Z,v);

My problem is to calculate the area for a given altitude (in my code for example 910). I have problems to read the contour matrix. I would like to calculate the Area with the following code (x and y are the contour coordinates for a given altitude):

    area = areaint(x,y,referenceEllipsoid('GRS80','km'));

Is there a possibility to calculate the area for a given altitude with the code above (maybe from the contour matrix)?

(I also would like to calculate the volume between two altitudes: do you have an idea to calculate this volume?)

Thank you!