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ntia-location extension v1.0.0

The ntia-location namespace provides metadata to describe a coordinate system and specify location.

ntia-location is fully compliant with the SigMF specification and conventions. ntia-location SHOULD be used instead of lat/long in sigmf-core.

1 Global

ntia-location defines the CoordinateSystem, ProjectedCoordinateSystem , GeographicCoordinateSystem, Datum, Spheroid, and Location objects and extends the Global with the following name/value pairs:

name required type unit description
coordinate_system false CoordinateSystem N/A Unique ID for coordinate system.

1.1 CoordinateSystem Object

The base CoordinateSystem object used to describe the coordinate system.

name required type unit description
id true string N/A Unique ID for the coordinate system.
description false string N/A Description of the coordinate system.
coordinate_system_type true string N/A Type of the coordinate system: CoordinateSystem, GeographicCoordinateSystem, or ProjectedCoordinateSystem
distance_unit true string N/A Unit of horizontal distance for coordinate system. E.g. Meters, feet, decimal degrees, DMS, city blocks.
time_unit true string N/A Unit of time for speed measurements. E.g. Hours, seconds.
origin false string N/A Origin of cartesian coordinate system. E.g. State of CO, survey marker #MT 127.
orientation_ref false string N/A Reference vector for orientation. E.g. Magnetic north
orientation false string N/A Rotation of cartesian coordinate system, from orientation_ref (in degrees). E.g. Annotating values as true north instead of magnetic north by including a magnetic declination (0,0,0.35)
elevation_ref false string N/A Elevation reference datum. E.g. Mean Sea Level, Above ground level, Antenna elevation.
elevation_unit false string N/A Unit of elevation for coordinate system. E.g. Meters, feet.

1.2 ProjectedCoordinateSystem Object

The ProjectedCoordinateSystem object extends CoordinateSystem and adds the following properties:

name required type unit description
false_easting false double N/A False easting of PCS.
false_northing false double N/A False northing of PCS.
central_meridian false double N/A Central meridian of PCS.
scale_factor false double N/A Scale factor of PCS.
origin_latitude false double decimal degrees Latitude of origin of PCS.
projection false string N/A Type of projection. E.g. Conical, cylindrical, transverse mercator.
gcs false GeographicCoordinateSystem N/A Underlying geographic coordinate system of PCS.

1.3 GeographicCoordinateSystem Object

A GeographicCoordinateSystem extends CoordinateSystem and adds the following properties:

name required type unit description
datum false Datum N/A Datum of spheroid or sphere. E.g. NAD27, NAD83, WGS84

1.4 Datum Object

Datum has the following properties:

name required type unit description
id false string N/A Unique ID for datum, the ESPG number is RECOMMENDED.
description false string N/A Description of datum.
spheroid false Spheroid N/A Underlying sphere or spheroid of datum.

1.5 Spheroid Object

Spheroid covers the definition of both a sphere or a spheroid. It has the following properties:

name required type unit description
id false string N/A Unique ID for the spheroid, the ESPG number is RECOMMENDED.
description false string N/A Description of the spheroid. Eg. Clarke 1866, WGS84
semiminor false double N/A Semiminor axis radii of spheroid.
semimajor false double N/A Semimajor axis radii of spheroid.
flattening false double N/A Flattening value of spheroid.
angular_unit false string N/A Angular unit of measure of spheroid. E.g. degrees, radians, grads
prime_meridian false string N/A The name of the prime meridian.
meridian_offset false double N/A The offset of the prime meridian from Greenwich in degrees.

1.6 Location Object

The Location object is used within the Sensor, and Emitter objects to specify their locations. The Location object has the following properties:

name required type unit description
x false double N/A Location of object releative to x-axis origin. MUST contain longitude for a Geographic Coordinate System.
y false double N/A Location of object releative to y-axis origin. MUST contain latitude for a Geographic Coordinate System.
z false double N/A Location of object releative to z-axis origin.
speed false double distance_unit/time_unit Speed.
bearing false double degrees Direction (angle relative to orientation_ref).
description false string N/A A brief textual description of the location.

2 Captures

ntia-location does not provide additional keys to Captures.

3 Annotations

ntia-location does not extend Annotations.

4 Example

4.1 GeographicCoordinateSystem - Simple

  "global": {
    "core:datatype": "rf32_le",
    "core:sample_rate": 15360000,
    "ntia-scos:task_id": 418350,
    "ntia-location:coordinate_system": {
      "coordinate_system_type": "GeographicCoordinateSystem",
      "id": "WGS 1984",
      "distance_unit": "km",
      "time_unit": "hours",
      "elevation_unit": "km"
    }
    "ntia-sensor:sensor": {
      "id":"Greyhound 10",
      "location" : {
        "x": -106.5,
        "y": 40.5
      }
    }
  },
  "captures": [
    {
      "core:sample_start": 0,
      "core:frequency": 700000000,
      "core:datetime": "2019-12-12T22:01:59.000310Z"
    }
  ],
  "annotations": [
    ...
  ]
}

4.2 Geographic Coordinate System - Complex

{
  "global": {
    "core:datatype": "rf32_le",
    "core:sample_rate": 15360000,
    "ntia-scos:task_id": 212393,
    "ntia-location:coordinate_system": {
      "coordinate_system_type": "GeographicCoordinateSystem",
      "id": "EPSG:4326",
      "description": "World Geodetic System 1984 - Horizontal component of 3D system. Used by the GPS satellite navigation system and for NATO military geodetic surveying.",
      "datum": {
        "spheroid": {
          "semiminor": 6356752.3142,
          "semimajor": 6378137.0,
          "flattening": 0.0033528106647474805,
          "prime_meridian": "Greenwich",
          "meridian_offset": 0.0
        }
      }
    },
    "ntia-sensor:sensor": {
      "id":"Greyhound 10",
      "location" : {
        "x": -106.5,
        "y": 40.5
      }
    }
  },
  "captures": [
    {
      "core:sample_start": 0,
      "core:frequency": 700000000,
      "core:datetime": "2019-12-13T21:58:14.000587Z"
    }
  ],
  "annotations": [
    
  ]
}

4.3 Projected Coordinate System

{
  "global": {
    "core:datatype": "rf32_le",
    "core:sample_rate": 15360000,
    "ntia-scos:task_id": 392566,
    "ntia-location:coordinate_system": {
      "coordinate_system_type": "ProjectedCoordinateSystem",
      "id": "EPSG:2029",
      "description": "NAD27(76) / UTM zone 17N",
      "gcs": {
        "coordinate_system_type": "GeographicCoordinateSystem",
        "id": "EPSG:4608",
        "description": "NAD27(76)"
      }
    },
    "ntia-sensor:sensor": {
      "id":"Greyhound 10",
      "location" : {
        "x": -106.5,
        "y": 40.5
      }
    }  
  },
  "captures": [
    {
      "core:sample_start": 0,
      "core:frequency": 700000000,
      "core:datetime": "2019-12-12T22:01:59.000304Z"
    }
  ],
  "annotations": [
    ...
  ]
}