How to remove offset

I would like to remove offset from my map , when I plot map the pixel get outside border.

latitude=[-89.75:0.5:89.75]'; longitude=[-179.75:0.5:179.75] & I have z values on 0.5 grid

so I can remove offset from my map ? I used axesm eqdcylin load coast h=surfacem(latitude,longitude,log10(vec1)')