code: function inverse$15(p) {
          p.x -= this.x0;
          p.y -= this.y0;
          var lon, lat;
  
          if (this.sphere) {
              lon = adjust_lon(this.long0 + (p.x / this.a) / Math.cos(this.lat_ts));
              lat = Math.asin((p.y / this.a) * Math.cos(this.lat_ts));
          }
          else {
              lat = iqsfnz(this.e, 2 * p.y * this.k0 / this.a);
              lon = adjust_lon(this.long0 + p.x / (this.a * this.k0));
          }
  
          p.x = lon;
          p.y = lat;
          return p;
      }
docs: /* Cylindrical Equal Area inverse equations--mapping x,y to lat/long
  ------------------------------------------------------------