Table 5.18 -- EDCS Classifications whose label begins with O
| Label | Definition | Related concepts | Code |
| OASIS | A small, isolated, fertile or green site in a desert region usually having a spring or well. | 573 | |
| OBJECT_CHARSET | A set of characteristics describing an object, which are organized by characteristic. | 574 | |
| OBSERVATORY | A building designed and equipped for making observations of astronomical, meteorological, or other natural phenomena. | EC ACOUSTIC_STATION, EC ASTRONOMICAL_STATION, EC GAUGING_STATION, EC MAGNETIC_STATION, EC WEATHER_STATION | 575 |
| OC_ACOUSTIC_ACTHIGH_CHARSET | A set of acoustic characteristics of discretely reflected acoustic energy (active highlights) off of an object in the ocean. | EC OCEAN_ACOUSTIC_CHARSET | 576 |
| OC_ACOUSTIC_NOISE_CHARSET | A set of acoustic noise source characteristics (e.g., frequency domain specification) of an ocean region or location. | EC OCEAN_ACOUSTIC_CHARSET | 577 |
| OC_ANALYSIS_CHARSET | A set of characteristics of the ocean determined through a process of analysis, e.g., salinity, surface temperature, or wave height. | 578 | |
| OC_ANALYSIS_SURFACE_CHARSET | A set of characteristics of the ocean (e.g., salinity, or temperature) determined through a process of analysis, which are associated with a specific type of generally horizontal surface, e.g., mean sea level, or constant depth. | EC OC_ANALYSIS_CHARSET | 579 |
| OC_ANALYSIS_VOLUME_CHARSET | A set of characteristics of the ocean (e.g., salinity, or temperature) determined through a process of analysis, which occur within a three-dimensional region. | EC OC_ANALYSIS_CHARSET | 580 |
| OC_COLUMN_SCATSTRN_CHARSET | A set of acoustic scattering strength characteristics of the ocean along a columnar segment. | EC OCEAN_SCATSTRN_CHARSET | 581 |
| OC_HF_ACOUSTIC_LOSS_CHARSET | A set of high frequency acoustic loss characteristics of the ocean floor, e.g., sediment type and thickness. | EC OCEAN_ACOUSTIC_CHARSET | 582 |
| OC_LAYER_SCATSTRN_CHARSET | A set of acoustic scattering strength characteristics of the ocean along a horizontal layer. | EC OCEAN_SCATSTRN_CHARSET | 583 |
| OC_LF_ACOUSTIC_LOSS_CHARSET | A set of low frequency acoustic loss characteristics of the ocean floor, e.g., sediment type and thickness. | EC OCEAN_ACOUSTIC_CHARSET | 584 |
| OC_NOISE_AMBIENT_CHARSET | A set of ambient acoustic noise characteristics of the ocean, i.e., composite noise from all sources. | 585 | |
| OC_NOISE_MIZ_CHARSET | A set of acoustic noise characteristics of the ocean due to the marginal zone of polar ice. | 586 | |
| OC_NOISE_RAIN_CHARSET | A set of acoustic noise characteristics of the ocean due to rain hitting the ocean surface. | 587 | |
| OC_NOISE_RESIDUAL_CHARSET | A set of residual ambient acoustic noise characteristics of the ocean not otherwise attributable to a specific category. | 588 | |
| OC_NOISE_SEA_STATE_CHARSET | A set of acoustic noise characteristics of the ocean due to sea state (i.e., surface wave action); also called wind noise. | 589 | |
| OC_NOISE_SHIPPING_CHARSET | A set of acoustic noise characteristics of the ocean due to distant shipping. | 590 | |
| OCCLUDED_FRONT | A composite of two weather fronts formed as a cold front overtakes a warm front or a quasi-stationary front, i.e., a cold, warm, or neutral occlusion. | EC COLD_FRONT, EC WARM_FRONT | 591 |
| OCCUPATION_ZONE | A region temporarily held and controlled by a foreign military force. | 592 | |
| OCEAN | The entire body of salt water that covers a planetary surface. In the case of the Earth, it is principally divided into the Atlantic, Pacific, and Indian oceans, their southern extensions in Antarctica, and the Arctic Ocean. | EC OCEAN_BASIN, EC WATER_EXCEPT_INLAND | 593 |
| OCEAN_ACOUSTIC_CHARSET | A set of acoustic characteristics of the ocean, e.g., salinity, shipping noise, or sound speed. | EC OCEAN | 594 |
| OCEAN_ACOUSTIC_SIGNATURE | An acoustic frequency domain specification of a signal source in the ocean. | EC OCEAN_ACOUSTIC_CHARSET | 595 |
| OCEAN_ACOUSTIC_TGTSTRN | The amount of signal excess added to the return energy of an active sonar emission based on the reflective characteristics of an object in the ocean. | EC OCEAN_ACOUSTIC_CHARSET | 596 |
| OCEAN_BASIN | A delimited, principal division of planetary oceans, e.g., Arctic, Atlantic, Pacific, or Indian, in the case of the Earth. | EC OCEAN, EC WATER_EXCEPT_INLAND | 597 |
| OCEAN_BIOLOGIC | An object in the ocean of biological nature, e.g., a fish school, kelp bed, or whale pod. | 598 | |
| OCEAN_CURRENT | A large volume region of the ocean containing moving water which is relatively homogenous with respect to temperature or salinity characteristics, and which differ from those of the surrounding water. | 599 | |
| OCEAN_EDDY | A localized large volume region of the ocean containing moving water which has spun off of an ocean current and which is relatively homogenous with respect to temperature or salinity characteristics, and which differs in those characteristics of the surrounding water. | EC EDDIES | 600 |
| OCEAN_FLOOR_BATHYMETRY | Pertaining to the depth of the ocean floor with respect to a defined vertical datum. | 601 | |
| OCEAN_FLOOR_PINNACLE | A significant configuration of underwater bottom topography generally round in shape as viewed from above and of reduced depth at its centre; also called a seamount. | EC BOTTOM_TOPO_CONFIGURATION | 602 |
| OCEAN_FLOOR_REGION | A bathymetric region underlying the ocean surface. | EC OCEAN_SURFACE_REGION, EC WATER_EXCEPT_INLAND | 603 |
| OCEAN_FLOOR_RIDGE | A significant configuration of underwater bottom topography generally linear in shape as viewed from above and of reduced depth along its axis. | EC BOTTOM_TOPO_CONFIGURATION | 604 |
| OCEAN_FLOOR_TRENCH | A significant configuration of underwater bottom topography generally linear in shape as viewed from above and of increased depth along its axis. | EC BOTTOM_TOPO_CONFIGURATION | 605 |
| OCEAN_FRCST_CHARSET | A set of forecasted characteristics of the ocean, e.g., wave height and direction. | 606 | |
| OCEAN_FRCST_SURFACE_CHARSET | A set of forecasted characteristics of the ocean associated with a specific type of generally horizontal surface, e.g., mean sea level, or constant depth. | EC OCEAN_FRCST_CHARSET | 607 |
| OCEAN_FRCST_VOLUME_CHARSET | A set of forecasted characteristics of the ocean occurring within a three-dimensional region, e.g. salinity, or temperature. | EC OCEAN_FRCST_CHARSET | 608 |
| OCEAN_REVERB_CHARSET | A set of acoustic reverberation characteristics of the ocean. | 609 | |
| OCEAN_REVERB_FLOOR_CHARSET | A set of acoustic reverberation characteristics of the ocean floor. | EC OCFLR_CHARSET, EC OCEAN_REVERB_CHARSET | 610 |
| OCEAN_REVERB_SRF_CHARSET | A set of acoustic reverberation characteristics of the ocean surface. | EC OCEAN_REVERB_CHARSET, EC OCEAN_SURFACE_CHARSET | 611 |
| OCEAN_REVERB_VOLUME_CHARSET | A set of acoustic reverberation characteristics of the ocean volume. | EC OCEAN_REVERB_CHARSET, EC OCEAN_VOLUME_CHARSET | 612 |
| OCEAN_SCATSTRN_CHARSET | A set of acoustic scattering strength characteristics of the ocean. | 613 | |
| OCEAN_SNDSPD_CHARSET | A set of sound speed related characteristics of the ocean water, e.g., temperature, salinity, pressure, or associated climatological statistics. | 614 | |
| OCEAN_SURFACE_CHARSET | A set of characteristics of the ocean surface, e.g., sea state, wind speed, or wind direction. | 615 | |
| OCEAN_SURFACE_REGION | A region of the ocean surface. | EC OCEAN | 616 |
| OCEAN_TEMPERATURE_CHARSET | A set of temperature-related characteristics of the ocean water, e.g., temperature statistics, gradient, thermocline, or layering. | 617 | |
| OCEAN_VOLUME_CHARSET | A set of characteristics of the ocean volume exclusive of the ocean surface or ocean floor, e.g., currents, salinity, or temperature. | 618 | |
| OCEAN_WATER_CHARACTERISTIC | A characteristic of the ocean water, e.g., pH, specific gravity, translucence, or salinity. | 619 | |
| OCFLR_ACOUSTIC_CHARSET | A set of acoustic characteristics of the ocean floor, e.g., sediment refractivity. | EC BOTTOM_CHARACTERISTIC | 620 |
| OCFLR_ACOUSTIC_LOSS_CHARSET | A set of acoustic loss characteristics of the ocean floor, e.g., sediment type and thickness. | EC OCEAN_ACOUSTIC_CHARSET | 621 |
| OCFLR_CHARSET | A set of characteristics of the ocean floor, e.g., bathymetry, a ridge, or a trench. | 622 | |
| OCSRF_ACOUSTIC_LOSS_CHARSET | A set of acoustic loss characteristics of the ocean surface, e.g., surface roughness. | EC OCEAN_ACOUSTIC_CHARSET | 623 |
| OCSRF_SHIPPING_CHARSET | A set of characteristics of surface ships or vessels traversing the ocean. | 624 | |
| OFF_ROUTE_BEARING | The direction (bearing) and distance from a NAVAID to a defined waypoint. | 625 | |
| OFFSHORE_LOADING_FACILITY | A site and associated structures located offshore for loading and unloading cargo. | EC OFFSHORE_PLATFORM | 626 |
| OFFSHORE_PLATFORM | A structure placed in the sea and used for production loading and discharge, or observation/research facilities. | EC OFFSHORE_LOADING_FACILITY | 627 |
| OIL_BARRIER | A construction to stop and contain oil flow on water. | EC BOOM, EC LOG_BOOM | 628 |
| OPEN_WATER | A region of surface water that is flowing or free standing, e.g., a lake, reservoir, river, canal, sea, or ocean. | EC CANAL, EC LAKE, EC OCEAN, EC RESERVOIR, EC RIVER | 629 |
| OPERA_HOUSE | A building which houses a theatre designed chiefly for the performance of operas. | EC THEATRE | 630 |
| ORCHARD | A tract of land devoted to the cultivation of fruit or nut trees. | EC PLANTATION | 631 |
| ORCHARD_OR_PLANTATION | A tract of land covered by systematic plantings of trees that yield fruits, nuts or other products. May be further delineated specifically as EC ORCHARD or EC PLANTATION. | EC CROP_LAND, EC HOP_FIELD, EC VINEYARDS | 632 |
| ORE_REFINERY | An industrial plant for purifying ores and extracting from them various metal and chemical products, e.g., copper or silver. | 633 | |
| OUTBUILDING | A small building, separate from but located near, the main building; e.g., an outdoors latrine or outhouse. | 634 | |
| OVEN | A chamber or enclosed compartment for heating, baking, or roasting food, as in a stove. | EC KILN | 635 |
| OVERFALL_REGION | An expanse of water where short, breaking waves are formed on the surface when a strong current passes over a shoal or other submarine obstruction or meets a contrary current or wind. | EC BOMBORA_REGION, EC BREAKER_REGION, EC TIDE_RIP_REGION | 636 |
| OVERHEAD_CABLE | An insulated wire or group of wires formed into one continuous strand and located above ground or above water surface. | EC BURIED_POWER_TRNS_LINE, EC CABLE, EC POWER_TRNS_LINE | 637 |
| OVERHEAD_OBSTRUCTION | An overhead obstruction, e.g., an underpass, overhead pipeline, building overhang, or other covered travelled way. | 638 | |
| OVERPASS | A bridge or viaduct used to provide clearance to traffic at a lower elevation. | EC BRIDGE | 639 |