axesm mercator
mstruct = gcm

mstruct = 
     mapprojection: 'mercator'
              zone: []
        angleunits: 'degrees'
            aspect: 'normal'
     falsenorthing: 0
      falseeasting: 0
       fixedorient: []
             geoid: [1 0]
       maplatlimit: [-86 86]
       maplonlimit: [-180 180]
      mapparallels: 0
        nparallels: 1
            origin: [0 0 0]
       scalefactor: 1
           trimlat: [-86 86]
           trimlon: [-180 180]
             frame: 'off'
             ffill: 100
        fedgecolor: [0 0 0]
        ffacecolor: 'none'
         flatlimit: [-86 86]
        flinewidth: 2
         flonlimit: [-180 180]
              grid: 'off'
         galtitude: Inf
            gcolor: [0 0 0]
        glinestyle: ':'
        glinewidth: 0.5000
    mlineexception: []
         mlinefill: 100
        mlinelimit: []
     mlinelocation: 30
      mlinevisible: 'on'
    plineexception: []
         plinefill: 100
        plinelimit: []
     plinelocation: 15
      plinevisible: 'on'
         fontangle: 'normal'
         fontcolor: [0 0 0]
          fontname: 'Helvetica'
          fontsize: 10
         fontunits: 'points'
        fontweight: 'normal'
       labelformat: 'compass'
     labelrotation: 'off'
        labelunits: 'degrees'
     meridianlabel: 'off'
    mlabellocation: 30
    mlabelparallel: 86
       mlabelround: 0
     parallellabel: 'off'
    plabellocation: 15
    plabelmeridian: -180
       plabelround: 0