Table 6.16 -- EDCS Attributes whose label begins with M
| Label | Definition | Attribute value type | EQ label | Related concepts | Code |
| MAGNETIC_AZIMUTH | The horizontal angle, measured in a clockwise direction from above, from planetary geodetic north to the direction to a position or object. | REAL | PLANE_ANGLE | 507 | |
| MAGNETIC_FIELD_KP | The quantity of the logarithmic planetary index of geomagnetic activity, representing a single planetary value measuring the two horizontal (x, y) components of the magnetic field. A pseudo logarithmic scale, Kp = 0 represents a 2,5 nanotesla variation from the quiet day value, and Kp = 9 represents a 666 nanotesla variation. | REAL | PURE_NUMBER | 508 | |
| MAGNETIC_FIELD_NORMAL | The strength of the planetary magnetic field as measured in orbit, in the direction normal to the plane formed by the satellite spin axis and the direction of the planet. | REAL | MAGNETIC_FLUX_DENSITY | 509 | |
| MAGNETIC_FIELD_PARALLEL | The strength of the planetary magnetic field as measured in orbit, in the direction parallel to the satellite spin axis. | REAL | MAGNETIC_FLUX_DENSITY | 510 | |
| MAGNETIC_FIELD_PLANETWARD | The strength of the planetary magnetic field as measured in orbit, in the direction of the planet. | REAL | MAGNETIC_FLUX_DENSITY | 511 | |
| MAGNETIC_LOCAL_TIME | Time calculated as magnetic longitude divided by 15, in hours, added to the local (geodetic) time of the magnetic prime meridian. | REAL | TIME | 512 | |
| MAGNETIC_VARIATION | The horizontal angle between planetary geodetic north and magnetic north measured east (positive value) or west (negative value) according to whether magnetic north lies east or west of planetary geodetic north. | REAL | PLANE_ANGLE | 513 | |
| MAGNETIC_VARIATION_ANOMALY | The difference between the magnetic variation of the disturbance region and the magnetic variation of the surrounding region. | REAL | PLANE_ANGLE | 514 | |
| MAGNETOSPHERE_PLASMA_FLUX | The total flux of charged particles in the planetary magnetosphere. | REAL | PARTICLE_FLUX_DENSITY | 515 | |
| MAINT_FACILITIES_AVAILABLE | The type of maintenance facilities available at or in the near vicinity. | ENUMERATION | 516 | ||
| MAINTAINED | Indicates that the object is maintained. | LOGICAL | 517 | ||
| MANEUVER_DAMAGE | The extent of physical injury/damage to the capability to maneuver (e.g., mobility or propulsion), in terms of fractional degradation from a fully capable state. The following interpretations may be applied: 1/4: Minor Reduction, 2/4: Moderate Reduction, 3/4: Severe Reduction, 4/4: Immobile. | REAL | PURE_NUMBER | 518 | |
| MAP_OBJECT_IDENTIFIER | The numeric identifier of specific interior map/chart graphical objects; used for linking to border information, an external database or reference. | INDEX | 519 | ||
| MARGINAL_ICE_ZONE_COVERAGE | The marginal ice zone extent of coverage. | ENUMERATION | 520 | ||
| MARINER_NOTICE_DATE | The publication date of a Notice To Mariners; coded as specified by ISO 8601:1988, 5.2.1.1. | STRING | 521 | ||
| MARITIME_BOUNDARY_LIMIT | A designation applied to the boundary of a maritime region that describes some aspect of the boundary line. | ENUMERATION | 522 | ||
| MARITIME_CONSTRUCTION_TYPE | The type of construction used for a maritime object. | ENUMERATION | 523 | ||
| MARITIME_REGION_TYPE | A designation applied to a maritime region that describes some aspect of that region of significance to maritime operations. | ENUMERATION | 524 | ||
| MARITIME_STATION_TYPE | The equipment or activity at site. | ENUMERATION | 525 | ||
| MARITIME_TRACK_TYPE | The restrictions, direction and other characteristics of maritime tracks. | ENUMERATION | 526 | ||
| MASS_EXTINCTION_COEFFICIENT | The extinction coefficient divided by the transmission medium's density. This is also equivalent to the natural logarithm of transmissivity divided by length of propagation and again by density. Units dimension for the mass extinction coefficient is area divided by mass. The mass extinction coefficient may be qualified by other attributes, e.g., the electromagnetic band for which the value applies. | REAL | MASS_ATTENUATION_COEFF | 527 | |
| MAST_TYPE | The type of a mast. | ENUMERATION | 528 | ||
| MATERIAL_DENSITY | The mass per unit volume of a material. | REAL | VOLUMIC_MASS | 529 | |
| MAX_OMNIDIR_SNOISE_SPECPL | The highest omni directional shipping noise spectral power level measured in a region; typically taken at 50 hertz; this quantity may be qualified by the frequency of the 1 Hz band and an ocean location. | REAL | PRESSURE_POWER_LEVEL | 530 | |
| MAXIMUM_ACHIEVABLE_TEMP | The maximum temperature a particular material or object can achieve. | REAL | THERMO_TEMPERATURE | 531 | |
| MAXIMUM_AIR_TEMP_PERIOD | The time period for which the maximum temperature was recorded. | REAL | TIME | 532 | |
| MAXIMUM_AIR_TEMPERATURE | The maximum air temperature that occurred during the measurement period. | REAL | THERMO_TEMPERATURE | 533 | |
| MAXIMUM_AUTHORIZED_ALTITUDE | The highest altitude in an airway or route at which adequate reception of NAVAID signals is assured. | STRING | 534 | ||
| MAXIMUM_BREAKER_HEIGHT | The mean height of the highest tenth of surf zone waves, measured from trough to crest. | REAL | LENGTH | 535 | |
| MAXIMUM_CONTOUR_ELEVATION | The maximum value of a depth curve polygon. | REAL | LENGTH | 536 | |
| MAXIMUM_CURRENT_SPEED | Maximum speed of water flow (current). | REAL | VELOCITY | 537 | |
| MAXIMUM_DEPTH_RANGE | The maximum value of a depth range. | REAL | LENGTH | 538 | |
| MAXIMUM_DEWPOINT_TEMP | The maximum dew-point temperature from a series of samples taken during the reporting period. | REAL | THERMO_TEMPERATURE | 539 | |
| MAXIMUM_FLIGHT_LEVEL | A maximum surface of constant atmospheric pressure which is related to a specific pressure datum (1 013,2 hectopascal (760 millimetres of mercury)), and is separated from the consecutive flight levels by a pressure interval corresponding to 152,4 metres (500 feet). | REAL | LENGTH | 540 | |
| MAXIMUM_ICE_KEEL_DRAFT | The maximum ice keel draft within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 541 | |
| MAXIMUM_OCEAN_TEMP_1_STDV | The temperature that is one standard deviation above the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 542 | |
| MAXIMUM_OCEAN_TEMP_2_STDV | The temperature that is two standard deviations above the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 543 | |
| MAXIMUM_OCEAN_TEMP_3_STDV | The temperature that is three standard deviations above the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 544 | |
| MAXIMUM_SURFACE_ELEVATION | The maximum elevation of the terrain surface with respect to a specified vertical datum. | REAL | LENGTH | 545 | |
| MAXIMUM_VERTICAL_CLEARANCE | The greatest distance between the travelled way and any obstruction vertically above it. | REAL | LENGTH | 546 | |
| MAXIMUM_VOLTAGE | The maximum voltage available on the line. | REAL | ELECTRIC_POTENTIAL | 547 | |
| MAXIMUM_WAVE_HEIGHT | The mean height of the highest tenth of waves measured from trough to crest. | REAL | LENGTH | 548 | |
| MAXIMUM_WIND_GUST_SPREAD | The difference between adjacent wind speed peaks and lulls. | REAL | VELOCITY | 549 | |
| MEAN_AIR_DENSITY_CLIM | The mean historical ratio of the mass of air to the volume it occupies. | REAL | VOLUMIC_MASS | 550 | |
| MEAN_AIR_DENSITY_CLIM_STDV | The quantity of the standard deviation of the historical air density. | REAL | VOLUMIC_MASS | 551 | |
| MEAN_AIR_TEMP | The mean air temperature during the measurement period. | REAL | THERMO_TEMPERATURE | 552 | |
| MEAN_AIR_TEMP_CLIM | The mean historical temperature of the air. | REAL | THERMO_TEMPERATURE | 553 | |
| MEAN_AIR_TEMP_CLIM_STDV | The standard deviation of the historical air temperature. | REAL | THERMO_TEMPERATURE | 554 | |
| MEAN_AIR_TEMP_MAX_DIF_CLIM | The historical quantity of maximum difference between the mean temperature at an initial time and the mean temperature at an offset from that time. | REAL | THERMO_TEMPERATURE | 555 | |
| MEAN_AIR_TEMP_MIN_DIF_CLIM | The historical quantity of minimum difference between the mean temperature at an initial time and the mean temperature at an offset from that time. | REAL | THERMO_TEMPERATURE | 556 | |
| MEAN_AIR_TEMPDF_CLIM | The historical quantity of mean difference between the mean temperature at an initial time and the mean temperature at an offset from that time. | REAL | THERMO_TEMPERATURE | 557 | |
| MEAN_CLOUD_DROP_DIAMETER | The mean diameter of the water drops in a cloud. | REAL | LENGTH | 558 | |
| MEAN_DEWPOINT_CLIM | The mean of the historical measured dewpoint temperatures. | REAL | THERMO_TEMPERATURE | 559 | |
| MEAN_DEWPOINT_CLIM_STDV | The standard deviation of the historical measured dewpoint temperatures. | REAL | THERMO_TEMPERATURE | 560 | |
| MEAN_DEWPOINT_TEMPERATURE | The mean temperature to which a given parcel of air must be cooled at constant pressure and water vapour content in order for saturation to occur. | REAL | THERMO_TEMPERATURE | 561 | |
| MEAN_GMAGFLD_DECL_ANGLE | The mean declination angle between magnetic north and geodetic north, typically averaged over one hour. | REAL | PLANE_ANGLE | 562 | |
| MEAN_GMAGFLD_EAST_COMP | The mean strength of the geodetic east vector component of the geomagnetic field, typically averaged over one hour. | REAL | MAGNETIC_FLUX_DENSITY | 563 | |
| MEAN_GMAGFLD_FULL_COMP | The mean strength of the full vector component of the geomagnetic field (vector sum of all components), typically averaged over one hour. | REAL | MAGNETIC_FLUX_DENSITY | EA MEAN_GMAGFLD_EAST_COMP, EA MEAN_GMAGFLD_NORTH_COMP, EA MEAN_GMAGFLD_VERTICAL_COMP | 564 |
| MEAN_GMAGFLD_HORIZ_COMP | The mean strength of the horizontal vector component of geomagnetic field (vector sum of east and north components), typically averaged over one hour. | REAL | MAGNETIC_FLUX_DENSITY | EA MEAN_GMAGFLD_EAST_COMP, EA MEAN_GMAGFLD_NORTH_COMP | 565 |
| MEAN_GMAGFLD_NORTH_COMP | The mean strength of the geodetic north vector component of the geomagnetic field, typically averaged over one hour. | REAL | MAGNETIC_FLUX_DENSITY | 566 | |
| MEAN_GMAGFLD_VERTICAL_COMP | The mean strength of the vertical vector component of geomagnetic field, typically averaged over one hour. | REAL | MAGNETIC_FLUX_DENSITY | 567 | |
| MEAN_GPOT_ALT_CLIM | The mean historical altitude of points in the atmosphere expressed into the geopotential of those altitudes. | REAL | GEOPOTENTIAL_ENERGY_LENGTH | 568 | |
| MEAN_GPOT_ALT_CLIM_STDV | The quantity of the standard deviation of historical geopotential altitudes. | REAL | GEOPOTENTIAL_ENERGY_LENGTH | 569 | |
| MEAN_ICE_DRAFT | The mean ice draft within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 570 | |
| MEAN_ICE_DRAFT_STDV | The standard deviation of mean ice draft within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 571 | |
| MEAN_ICE_KEEL_DRAFT | The mean ice keel draft within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 572 | |
| MEAN_ICE_KEEL_DRAFT_STDV | The standard deviation of ice keel draft within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 573 | |
| MEAN_ICE_KEEL_SEP | The mean distance between ice keels, measured between keel peaks, within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 574 | |
| MEAN_ICE_KEEL_SEP_STDV | The standard deviation of mean distance between ice keels within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 575 | |
| MEAN_OCEAN_TEMP | The average temperature of the ocean water. | REAL | THERMO_TEMPERATURE | 576 | |
| MEAN_OCEAN_TEMP_STDV | The standard deviation of the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 577 | |
| MEAN_PRIMARY_WAVE_PERIOD | The quantity of time required for two successive primary wave crests in the ocean wave spectra to pass a fixed point. | REAL | TIME | 578 | |
| MEAN_SECONDARY_WAVE_PERIOD | The quantity of time required for two successive secondary wave crests in the ocean wave spectra to pass a fixed point. | REAL | TIME | 579 | |
| MEAN_SOIL_EVPT_RATE | The rate of water loss from the soil due to evaporation and transpiration. | REAL | VOLUME_FLOW_RATE | 580 | |
| MEAN_SURFACE_ELEVATION | The mean elevation of the terrain surface with respect to a specified vertical datum. | REAL | LENGTH | 581 | |
| MEAN_SURFACE_ELEVATION_STDV | The standard deviation of the elevation of the terrain surface with respect to a specified vertical datum. | REAL | LENGTH | 582 | |
| MEAN_SWELL_WAVE_PERIOD | The average time required for two successive swell wave crests to pass a fixed point. | REAL | TIME | 583 | |
| MEAN_WATER_DEPTH | The average depth of the water from a specified vertical datum to the sea floor. Recorded values are positive numbers. | REAL | LENGTH | EA SOUNDING_DATUM, EA VERTICAL_DATUM | 584 |
| MEAN_WAVE_DIRECTION | The mean horizontal angle, measured in a clockwise direction from above, from planetary geodetic north to the direction from which significant waves (combined wind and swell) in the ocean spectra are arriving. | REAL | PLANE_ANGLE | 585 | |
| MEAN_WAVE_HEIGHT_STDV | The standard deviation of the apparent height of ocean surface waves measured from trough to crest. | REAL | LENGTH | 586 | |
| MEAN_WAVE_LENGTH | The average distance between two successive ocean wave crests. | REAL | LENGTH | 587 | |
| MEAN_WAVE_PERIOD | The average time required for two successive waves (wind and swell) in the ocean wave spectra to pass a fixed point. | REAL | TIME | 588 | |
| MEAN_WAVE_SWELL_DIRECTION | The horizontal angle, measured in a clockwise direction from above, from planetary geodetic north to the direction from which the swell waves are arriving. | REAL | PLANE_ANGLE | 589 | |
| MEAN_WAVE_SWELL_HEIGHT | The mean height of swell waves measured from trough to crest. | REAL | LENGTH | 590 | |
| MEAN_WIND_SPEED | The mean rate of horizontal travel of air past a fixed point during a measurement time interval. | REAL | VELOCITY | 591 | |
| MEAN_WIND_SPEED_STDV | The quantity of the standard deviation of wind speeds during a measurement time interval. | REAL | VELOCITY | 592 | |
| MEDIAN_WIDTH | The width of the divider between multiple lanes/rails. When extracted from hardcopy product, the measured distance at map scale between connecting, adjacent two-way road centrelines having divided roadbeds. | REAL | LENGTH | 593 | |
| MEDIAN_WIDTH_RANGE | A range indicating the presence and width of a divider between multiple lanes/tracks. | ENUMERATION | 594 | ||
| MERCHANT_VESSEL_COUNT | The number of merchant vessels (gross weight > 907 184,7 kilograms (1 000 tons); length > 18 metres) in a nominal 111,120 kilometres (60 nautical miles) square cell of ocean. | COUNT | 595 | ||
| MET_TRANSMISSIVITY_DISTANCE | The measured distance of a meteorological transmissivity observation. | REAL | LENGTH | 596 | |
| MET_TRANSMISSIVITY_WAVLGTH | The electromagnetic wavelength used for a meteorological transmissivity distance observation. | REAL | LENGTH | 597 | |
| MIDDLE_CLOUD_BASE_ALTITUDE | The altitude of the base of a mid-level cloud layer, relative to a vertical reference datum. Mid-level clouds are composed of water and are of the altostratus, altocumulus, and nimbostratus types. The altitude of the bases of these clouds range from about 1 980 to 7 010 metres (6 500 to 23 000 feet) in the mid-latitudes. | REAL | LENGTH | 598 | |
| MIDDLE_CLOUD_COVERAGE | The fraction of the sky dome that is covered by all middle level clouds, as observed from the ground. | REAL | PURE_NUMBER | 599 | |
| MIDDLE_CLOUD_COVERAGE_CLIM | The quantity of historical occurrences of middle cloud coverage, as observed by a ground observer. | INTEGER | PURE_NUMBER | 600 | |
| MIDDLE_CLOUD_TOP_ALTITUDE | The altitude of the top of a mid-level cloud layer, relative to a vertical reference datum. Mid-level clouds are composed of water and are of the altostratus, altocumulus, and nimbostratus types. The altitude of the bases of these clouds range from about 1 980 to 7 010 metres (6 500 to 23 000 feet) in the mid-latitudes. | REAL | LENGTH | 601 | |
| MIDDLE_CLOUD_TYPE | The type of middle level cloud. | ENUMERATION | 602 | ||
| MILITARY_BRIDGE_INFO | An unstructured text field used to identify and/or describe a bridge subject to preplanned military interdiction. | STRING | 603 | ||
| MILITARY_FORCE_ALLEGIANCE | The military alignment of the force responsible for the creation or maintenance of the man-made object. | ENUMERATION | 604 | ||
| MILITARY_USE | Type of military region. | ENUMERATION | 605 | ||
| MIN_OMNIDIR_SNOISE_SPECPL | The lowest omni directional shipping noise spectral power level measured in a region; typically taken at 50 hertz; this quantity may be qualified by the frequency of the 1 Hz band, and an ocean location. | REAL | PRESSURE_POWER_LEVEL | 606 | |
| MINE_ACOUSTIC_ACTUATION | The type of acoustic actuation of an explosive mine. | ENUMERATION | 607 | ||
| MINE_ACTUATION | The type of actuation of an explosive mine. | ENUMERATION | 608 | ||
| MINE_ALLEGIANCE | The military alignment of the force responsible for the creation or maintenance of an explosive mine. | ENUMERATION | 609 | ||
| MINE_CABLELESS_ACTUATION | The type of cableless control method of an explosive mine. | ENUMERATION | 610 | ||
| MINE_CHARGE_SIZE | The explosive charge of a ground mine. | ENUMERATION | 611 | ||
| MINE_CONTACT_ACTUATION | The type of independent contact actuation of an explosive mine. | ENUMERATION | 612 | ||
| MINE_CONTROL_METHOD | The type of actuation control method of an explosive mine. | ENUMERATION | 613 | ||
| MINE_DENSITY | The areal density of explosive mines within a minefield. | REAL | AREAL_ENTITY_DENSITY | 614 | |
| MINE_INDEPENDENT_ACTUATION | The type of independent actuation of an explosive mine. | ENUMERATION | 615 | ||
| MINE_INFLUENCE_ACTUATION | The type of actuation influences of an explosive mine. | ENUMERATION | 616 | ||
| MINE_INFO_ANTI_HUNTING | The type of explosive mine anti-hunting capability. | ENUMERATION | 617 | ||
| MINE_INFO_ANTI_RECOVERY | The type of anti-recovery capability of an explosive mine. | ENUMERATION | 618 | ||
| MINE_INFO_ANTI_SWEEP_WIRE | The type of anti-sweep wire capability of an explosive mine. | ENUMERATION | 619 | ||
| MINE_INFO_DEVICE_TYPE | The type of special capabilities of an explosive mine. | ENUMERATION | 620 | ||
| MINE_INFO_TYPE | The special information characteristic type of an explosive mine. | ENUMERATION | 621 | ||
| MINE_MAGNETIC_SENSITIVITY | The sensitivity of a magnetic activation explosive mine. | ENUMERATION | 622 | ||
| MINE_MOORED_POSITION_TYPE | The position type of a moored explosive mine. | ENUMERATION | 623 | ||
| MINE_OPERATIONAL_USE | The military operational utility of an explosive mine. | ENUMERATION | 624 | ||
| MINE_OTHER_ACTUATION_TYPE | The type of actuation, independent of other actuation methods, of an explosive mine. | ENUMERATION | 625 | ||
| MINE_OTHER_INFO_TYPE | The subsidiary information for an explosive mine. | ENUMERATION | 626 | ||
| MINE_OTHER_POSITION_TYPE | The position type of an explosive mine. | ENUMERATION | 627 | ||
| MINE_POSITION_TYPE | The type of position of an explosive mine. | ENUMERATION | 628 | ||
| MINE_STATUS | The status of an explosive mine | ENUMERATION | 629 | ||
| MINE_TACTICAL_USE | The military tactical utility of an explosive mine. | ENUMERATION | 630 | ||
| MINE_TRACK_IDENTIFIER | The numeric identifier of a mine track; used for linking to an external database or reference. | INDEX | 631 | ||
| MINE_TYPE | The type of a mine. | ENUMERATION | 632 | ||
| MINIMUM_AIR_TEMP | The minimum air temperature that occurred during the measurement period. | REAL | THERMO_TEMPERATURE | 633 | |
| MINIMUM_AIR_TEMP_PERIOD | The time period for which the minimum air temperature was recorded. | REAL | TIME | 634 | |
| MINIMUM_CONTOUR_ELEVATION | The minimum value of a depth curve polygon. | REAL | LENGTH | 635 | |
| MINIMUM_CURRENT_SPEED | Minimum speed of water flow (current). | REAL | VELOCITY | 636 | |
| MINIMUM_DEPTH_RANGE | The minimum value of a depth range. | REAL | LENGTH | 637 | |
| MINIMUM_DEWPOINT_TEMP | The minimum dew-point temperature from a series of samples taken during the reporting period. | REAL | THERMO_TEMPERATURE | 638 | |
| MINIMUM_ENROUTE_ALTITUDE | The lowest altitude between radio fixes which assures acceptable navigational signal coverage and meets obstacle clearing clearance requirements. | STRING | 639 | ||
| MINIMUM_FLIGHT_LEVEL | A minimum surface of constant atmospheric pressure which is related to a specific pressure datum (1 013,2 hectopascal (760 millimetres of mercury)), and is separated from the consecutive flight levels by a pressure interval corresponding to 152,4 metres (500 feet). | REAL | LENGTH | 640 | |
| MINIMUM_ICE_KEEL_DRAFT | The minimum ice keel draft within a nominal 111,120 kilometres (60 nautical miles) square cell of the ocean. | REAL | LENGTH | 641 | |
| MINIMUM_OBSTACLE_CLEARANCE | The lowest published altitude in effect along a route segment (e.g., between radio fixes on VOR airways, or off fairway routes), which meets obstacle clearance requirements for the entire route segment and which assures an acceptable navigation signal. | REAL | LENGTH | 642 | |
| MINIMUM_OCEAN_TEMP_1_STDV | The temperature that is one standard deviation below the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 643 | |
| MINIMUM_OCEAN_TEMP_2_STDV | The temperature that is two standard deviations below the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 644 | |
| MINIMUM_OCEAN_TEMP_3_STDV | The temperature that is three standard deviations below the mean ocean temperature. | REAL | THERMO_TEMPERATURE | 645 | |
| MINIMUM_SAFE_ALTITUDE | The minimum safe altitude, relative to MSL, which provides a 304,8 metre (1 000 foot) obstacle clearance within the airspace. | REAL | LENGTH | 646 | |
| MINIMUM_SURFACE_ELEVATION | The minimum elevation of the terrain surface with respect to a specified vertical datum. | REAL | LENGTH | 647 | |
| MINIMUM_TRAVELED_WAY_WIDTH | The minimum width of the travelled way, excluding hard pavements and shoulders. | REAL | LENGTH | 648 | |
| MINUTE_WITHIN_DAY | The ordinal index of the minute within the day, starting with the number "0" at midnight. | INTEGER | PURE_NUMBER | 649 | |
| MINUTE_WITHIN_HOUR | The ordinal index of the minute within the hour, starting with the number "0" at the beginning of the hour. | INTEGER | PURE_NUMBER | 650 | |
| MISSILE_SITE_TYPE | The class of missile at a site. | ENUMERATION | 651 | ||
| MISSING_COLLECTION_REASON | The reason data was not collected. | ENUMERATION | 652 | ||
| MISSING_INFORMATION_TYPE | The type of missing information. | ENUMERATION | 653 | ||
| MISSION_SPECIFIC_DAMAGE | The extent of physical injury/damage specific to the mission (e.g., critical sensor/emitter antenna or subsystem), in terms of fractional degradation from a fully capable state. The following interpretations may be applied: 1/4: Minor Reduction, 2/4: Moderate Reduction, 3/4: Severe Reduction, 4/4: Inoperable. | REAL | PURE_NUMBER | 654 | |
| MIXING_LAYER_DEPTH | The depth, measured from the sea surface, of the surface mixing layer. | REAL | LENGTH | 655 | |
| MIXING_LAYER_DEPTH_STDV | The standard deviation of depth of surface mixing layer within a set. | REAL | LENGTH | 656 | |
| MIXING_LAYER_TEMP_GRAD | The temperature gradient across the mixing layer at a particular location. | REAL | LINEIC_THERMO_TEMP_GRADIENT | 657 | |
| MIXING_LAYER_TEMP_GRAD_STDV | The standard deviation of surface mixing layer temperature gradient within a set. | REAL | LINEIC_THERMO_TEMP_GRADIENT | 658 | |
| MIXING_RATIO | In a system of moist air, the ratio of the mass of water vapour to the mass of dry air. | REAL | MASS_FRACTION | 659 | |
| MN_AIR_SEA_TEMPDF | The mean temperature difference between the air and the sea. | REAL | THERMO_TEMPERATURE | 660 | |
| MN_AIR_SEA_TEMPDF_CLIM_STDV | The standard deviation of the temperature difference between the air and the sea. | REAL | THERMO_TEMPERATURE | 661 | |
| MN_POTENTIAL_SOIL_EVPT_RATE | The rate of potential loss of water from the soil due to evaporation and transpiration. | REAL | VOLUME_FLOW_RATE | 662 | |
| MN_SEASONAL_HWTR_DEPTH | A range indicating the average seasonal high water depth. | ENUMERATION | 663 | ||
| MN_SEASONAL_HWTR_SPD_RANGE | A range indicating the average seasonal high water speed, estimated within delineation of an object (e.g., aqueduct, stream, river outflow region, or drainage canal), exclusive of high water due to runoff or low water due to drought. | ENUMERATION | 664 | ||
| MN_SEASONAL_LWTR_DEPTH | A range indicating the average seasonal low water depth. | ENUMERATION | 665 | ||
| MN_SEASONAL_LWTR_SPD_RANGE | A range indicating the average seasonal low water speed, estimated within delineation of an object (e.g., aqueduct, stream, river outflow region, or drainage canal), exclusive of high water due to runoff or low water due to drought. | ENUMERATION | 666 | ||
| MN_SOLAR_LONGWAVE_RADIATION | The average rate of long wave (4 to 80 micrometres) solar radiation incident on a surface over a period. | REAL | IRRADIANCE | 667 | |
| MN_WIND_INDUCED_WAVE_HEIGHT | The mean height of the wind waves measured from trough to crest. | REAL | LENGTH | 668 | |
| MN_WIND_INDUCED_WAVE_PERIOD | The average time required for two successive wind wave crests to pass a fixed point. | REAL | TIME | 669 | |
| MODIFIED_SURF_INDEX | A single dimensionless number which provides a relative measure of the conditions likely to be encountered in the surf zone. The Modified Surf Index provides a guide for judging the feasibility of landing operations for each type of landing craft. | REAL | PURE_NUMBER | 670 | |
| MONTH | The month of the year; one of the twelve divisions of the year according to the Gregorian calendar, varying from 28 to 31 days in length. | ENUMERATION | 671 | ||
| MOORING_CONNECTION_TYPE | The type of connection used in a mooring system. | ENUMERATION | 672 | ||
| MOORING_FACILITY_TYPE | The type of mooring/warping facility. | ENUMERATION | 673 | ||
| MORSE_CODE_EMITTED | The single character that is being emitted by a light, beacon, communications transmitter or other signalling device. | STRING | 674 | ||
| MOVEMENT_INDUCED_CONTRAIL | The fraction of maximum production rate of contrails, vapour trails, or other ionization phenomena induced by movement through the atmosphere. The following interpretations may be applied: 1/4: Small, 2/4: Medium, 3/4: Large, 4/4: Maximum. | REAL | PURE_NUMBER | 675 | |
| MTRL_HANDLING_FACILITIES | The material handling facilities available at or in the near vicinity | ENUMERATION | 676 | ||
| MULTIPLE | Indicates that the object represents more than one instance of the object type. | LOGICAL | 677 | ||
| MULTIPLE_OBSTRUCTION_LIGHTS | Indicates that multiple obstruction lights are associated with the object. | LOGICAL | 678 |