I have referenced this blog posting(in Korean) for the field fortification, though I drew it much taller. This kind of field fortifications, modeled after Japanese field fortifications witnessed during Imjin war, were mostly built with cavalry in mind. Lack of protection against cavalry was always one of the greatest weaknesses of Joseon dynasty Korean army, which was composed mostly of archers and handgonners (arquebusiers after Imjin war). Numerous methods were tried and adopted in attempt to remedy this issue, such as use of carts and portable cheval de frise, but no one could figure out the use of pikes, as the tradition of utilizing pikemen was more or less lost in Northeast Asia after Yuan domination.