How to remove needless ranges from the pcolor map?

I have three data - Lon(304x448), Lat(304x448), SIC(304x448)

And below is the code I used

lon=Lon(:);

lat=Lat(:);

x1=floor(min(lon));

x2=ceil(max(lon));

y1=floor(min(lat));

y2=ceil(max(lat));

lon1=[x1:0.05:x2];

lat1=[y1:0.05:y2];

[long,lati]=meshgrid(lon1,lat1);

sic=griddata(Lon,Lat,SIC,long,lati);

pcolor(lon1,lat1,sic)

shading flat

This way, the map looks like this

But it runs out the observation range.

Below is plotting the observation points on the picture 1.

What should I do to remove that range?

[KSSV]

Don't use ceil or floor to find min and max..only use min and max.