griddata not creating a smooth interpolation

I'm trying to create a surface using the following data

I've collected some rough data points, plotted in this figure (contours added for clarity)

However when I use griddata to interpolate and then mesh the values, the result isn't the 'hill shape' you'd expect, instead it is very uneven as seen below (data points in black)

the central section seems very smooth however both sides are a mess. I've tried the curve fitting app within matlab but the result is the same. Below is the code and data used:

Tmod=[50  100  150  175  200  240  245  245  245  245  245  245  245  245  230  200  150  125  110  100  60  50  35  25  20  20  20  20  25  30  50  100  150  200  230  230  230  230  230  230  230  230  200  150  125  100  75  55  50  45  45  45  45  45  70  100  150  185  200  200  200  200  200  200  200  150  100  70  60  55  55  55  55  100  150  165  170  170  165  160  155  150  100  80  75  70  65  90  110  125  130  125  125  115  100  80  75  75  100 ];
  wmod=[250  250  400  500  515  1000  1500  2000  2500  3000  3500  4000  4500  5000  5000  5000  5000  5000  5000  4900  4500  4300  4000  3500  3000  2500  2000  1500  1000  500  1000  600  750  1000  1500  2000  2500  3000  3500  4000  4500  4990  4990  4990  4990  4750  4500  4000  3800  3500  3000  2500  2000  1500  1000  950  1000  1500  2000  2500  3000  3500  4000  4500  4980  4980  4500  4000  3500  3000  2500  2000  1500  1400  1200  1500  2000  2500  3000  3500  4000  4100  4000  3500  3000  2500  2000  1500  1500  1500  2000  2500  3000  3500  3500  3000  2500  2000  1600];
  nmod=[86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  95  95  95  95  95  95  95  95  95  95  95  95  95  95  95  96  96  96  96  96  96  96  96  96  96  96];

[wq,Tq]=meshgrid(0:45:4500, 0:2.5:250);
nmap=griddata(wmod,Tmod,nmod,wq,Tq);
figure
mesh(wq,Tq,nmap)

Please let me know if anything is unclear - thanks in advance!

Answer 1

[Luke Farrand]

Having a similar problem! Would love some help!!

Answer 2

[KAE]

You may want to try an outside function, objmap, which lets you choose how smooth the map is in x and y, and how much error to allow at your measurement locations.

http://globec.whoi.edu/software/saga/objmap.m

http://mooring.ucsd.edu/software/matlab/doc/toolbox/datafun/objmap.html

[adeq123]

Do you have any example of how to use that function ? Can't really understand it from documentation.

Answer 3

[KSSV]

Try scatteredinterpolant.

Tmod=[50  100  150  175  200  240  245  245  245  245  245  245  245  245  230  200  150  125  110  100  60  50  35  25  20  20  20  20  25  30  50  100  150  200  230  230  230  230  230  230  230  230  200  150  125  100  75  55  50  45  45  45  45  45  70  100  150  185  200  200  200  200  200  200  200  150  100  70  60  55  55  55  55  100  150  165  170  170  165  160  155  150  100  80  75  70  65  90  110  125  130  125  125  115  100  80  75  75  100 ];
wmod=[250  250  400  500  515  1000  1500  2000  2500  3000  3500  4000  4500  5000  5000  5000  5000  5000  5000  4900  4500  4300  4000  3500  3000  2500  2000  1500  1000  500  1000  600  750  1000  1500  2000  2500  3000  3500  4000  4500  4990  4990  4990  4990  4750  4500  4000  3800  3500  3000  2500  2000  1500  1000  950  1000  1500  2000  2500  3000  3500  4000  4500  4980  4980  4500  4000  3500  3000  2500  2000  1500  1400  1200  1500  2000  2500  3000  3500  4000  4100  4000  3500  3000  2500  2000  1500  1500  1500  2000  2500  3000  3500  3500  3000  2500  2000  1600];
nmod=[86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  86  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  90  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  94  95  95  95  95  95  95  95  95  95  95  95  95  95  95  95  96  96  96  96  96  96  96  96  96  96  96];
[wq,Tq]=meshgrid(0:45:4500, 0:2.5:250);
% nmap=griddata(wmod,Tmod,nmod,wq,Tq);
F = scatteredInterpolant(wmod',Tmod',nmod') ;
nmap = F(wq,Tq) ; 
figure
mesh(wq,Tq,nmap)