▁is ▁to ▁fight ▁on ▁land , ▁on ▁the ▁other ▁hand , ▁is ▁a ▁ground ▁asset ▁and ▁is ▁represented ▁in ▁the ▁land ▁dimension . ▁ ▁Cl osed ▁frames ▁are ▁used ▁to ▁denote ▁the ▁land ▁and ▁sea ▁surface ▁dimensions , ▁frames ▁open ▁at ▁the ▁bottom ▁denote ▁the ▁air / space ▁dimension , ▁and ▁frames ▁open ▁at ▁the ▁top ▁denote ▁the ▁sub sur face ▁dimension . ▁ ▁An ▁unknown ▁battle ▁dimension ▁is ▁possible ; ▁for ▁example , ▁some ▁electronic ▁war fare ▁sign atures ▁( e . g ., ▁rad ar ▁systems ) ▁are ▁common ▁to ▁several ▁battle ▁dimensions ▁and ▁would ▁therefore ▁be ▁assigned ▁an ▁" Unknown " ▁battle ▁dimension ▁until ▁further ▁disc rim ination ▁becomes ▁possible . ▁Special ▁Forces ▁may ▁operate ▁in ▁any ▁dimension . ▁ ▁The ▁full ▁set ▁of ▁battle ▁dimensions ▁is , ▁in ▁asc ending ▁order ▁of ▁distance ▁from ▁Earth ▁center : ▁ ▁SO F ▁( F ) ▁ ▁Sea ▁sub sur face ▁( U ) ▁ ▁Sea ▁surface ▁( S ) ▁ ▁Gr ound ▁( G ) ▁ ▁Air ▁( A ) ▁ ▁Space ▁( P ) ▁ ▁Other ▁( X ) ▁ ▁Un known ▁( Z ) ▁The ▁m nem onic ▁for ▁this ▁ordering ▁is ▁" F uss - G ap ". ▁ ▁The ▁letter ▁in ▁parentheses ▁is ▁used ▁by ▁the ▁symbol ▁identification ▁coding ▁( S ID C ) ▁scheme ▁— ▁strings ▁of ▁ 1 5 ▁characters ▁used ▁to ▁transmit ▁symbols . ▁ ▁The ▁space ▁and ▁air ▁battle ▁dimensions ▁share ▁a ▁single ▁frame ▁shape . ▁In ▁the ▁ground ▁battle ▁dimension , ▁two