Modifiers matching obstruction:

• clear,
• layer,
• permanent,
• featureless,
• physical,
• terrestrial,
• bigger,
• vertical,
• opaque,
• solid,
• internal,
• temporary,
• unusual,
• common,
• hard,
• taller,
• hidden,
• overhead,
• visual,
• nearby,
• lateral,
• over,
• mechanical,
• rigid,
• metal,
• surrounding,
• electrical,
• underwater,
• tall,
• minor,
• topical,
• significant,
• under,
• artificial,
• current,
• raised,
• horizontal,
• environmental,
• adjacent,
• movable,
• upright,
• subsurface,
• past,
• dense,
• hazardous,
• major,
• spatial,
• natural,
• virtual,
• short,
• up,
• simple,
• external,
• immovable,
• structural,
• impenetrable,
• indoor,
• urethral,
• visible,
• relevant,
• underground,
• smaller,
• larger,
• elongated,
• lighted,
• multiple,
• large,
• linear,
• removable,
• insurmountable,
• small,
• outdoor,
• discrete,
• hydraulic,
• local,
• nasal,
• level,
• geographic,
• low,
• cooler,
• fixed,
• additional,
• isolated,
• typical,
• irregular,

Simple categories matching subsurface:

• material,
• structure,
• mineral,
• soil,
• area,
• imperfection,
• detail,
• condition,
• sorbent,
• feature,
• variable,
• facility,
• reservoir,
• measure,
• property,
• separation,
• layer,
• drain,
• process,
• resource,
• anomaly,
• obstruction,
• attribute,
• quantity,
• rock,
• installation,
• fluid,
• utility,
• void,
• defect,
• information,
• excavation,
• variation,
• data,
• cavity,
• liquid,
• component,
• stratum,
• artifact,
• object,
• construction,
• body,
• system,
• deposit,
• item,
• change,
• industry,
• platform,
• formation,