SatcomCoordinates.jl

Documentation for SatcomCoordinates.jl.

julia

const ForwardOrInverse{F <: AbstractCRSTransform} = Union{F, InverseTransform{<:Any, <:F}}

Union representing either a forward or reverse transform of F

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SatcomCoordinates.WithNumbertype Type

julia

const WithNumbertype{T} = Union{AbstractSatcomCoordinate{T}, AbstractCRSTransform{T}}

Union representing the types defined and exported by this package, which always have a numbertype as first parameter.

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SatcomCoordinates.AER Type

julia

struct AER{T} <: AbstractTopocentricPosition{T}

Represents a position in the Azimuth-Elevation-Range (AER) coordinate system, which is a local coordinate system centered at a point on or above the surface of an Ellipsoid. The Elevation and Azimuth angles are always defined w.r.t. the ENU CRS with the same origin. More specifically:

Properties

az::Deg{T}: Azimuth angle, defined angle in the XY (North-East) plane from the +Y (North) direction to the object, positive towards +X (East) direction. It is constrained to be in the range [-180°, 180°]
el::Deg{T}: Elevation angle, defined as the angle between the XY plane and the point being described by the AER coordinates, positive towards +Z (Up) direction. It is constrained to be in the range [-90°, 90°]
r::Met{T}: Range in meters between the origin of the ENU CRS and the point being described by the AER coordinates.

Basic Constructors

AER(az::ValidAngle, el::ValidAngle, r::ValidDistance)

ValidAngle is either a Real Number, or a subtype of Unitful.Angle. ValidDistance is either a Real Number, or a subtype of Unitful.Length.

If of the provided argument is NaN, the returned AER object will contain NaN for all fields.

Fallback constructors

All subtypes of P <: AbstractSatcomCoordinate can also be constructed using a Tuple or SVector as input, which will be splatted into the standard constructor for P

See also: ENU, NED.

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SatcomCoordinates.AbstractAffineCRSTransform Type

julia

AbstractAffineCRSTransform{T}

Abstract type representing an affine transform between two CRSs with numbertype T.

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SatcomCoordinates.AbstractCRSTransform Type

julia

AbstractCRSTransform{T}

Abstract type representing a coordinate transform between two CRSs with numbertype T.

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SatcomCoordinates.AbstractFieldValue Type

julia

AbstractFieldValue{U, CRS, T}

Abstract type representing the value of a physical field expressed in a specific coordinate reference system CRS, and whose components have an associated unit U and a numbertype T.

Concrete implementations of this subtype are expected to have a single inner field svector which is a SVector{N, T} (N being the number of dimensions of the referenced CRS) and define the BasicTypes.constructor_without_checks method as per other coordinates in order to exploit the convenience functions defined on this abstract type.

An example concrete type representing velocity in a 3D CRS can be implemented as follows (assuming to have Quantity, @u_str and dimension imported from Unitful, and SVector from StaticArrays):

julia

const U = typeof(u"m/s")
const D = dimension(u"m/s")

const V{T} = Quantity{T, D, U}

struct VelocityFieldValue{CRS <: AbstractPosition{<:Any, 3}, T} <: AbstractFieldValue{U, CRS, T}
    svector::SVector{3, T}

    BasicTypes.constructor_without_checks(::Type{VelocityFieldValue{CRS, T}}, sv::SVector{3, T}) where {CRS, T} = new{CRS, T}(sv)
end

fv = VelocityFieldValue{ECEF}(1, 2, 3)

@test fv.x == 1u"m/s"
@test fv.y == 2u"m/s"
@test fv.z == 3u"m/s"

@test raw_svector(fv) == SVector{3, Float64}(1, 2, 3)
@test raw_properties(fv) == (x=1, y=2, z=3)

Concrete subtypes

SatcomCoordinates.jl currently does not implement concrete subtypes of AbstractFieldValue, but only defines the following methods that work if concrete subtypes are impelemented as in the example above:

raw_svector(::AbstractFieldValue): Returns the svector field
raw_properties(::AbstractFieldValue): Returns a NamedTuple with the properties of the svector field
properties_names(::Type{<:AbstractFieldValue{U, CRS}}): Returns the property names of the CRS parametric type
Default constructor taking N numbers or a Tuple/Svector, with the values interpreted as quantities of unit U if not provided directly as quantitites
ConstructionBase.getproperties(::AbstractFieldValue{U, CRS}): Returns a NamedTuple with the properties of the field assuming the properties names of CRS and returning values with unit U.
Base.getproperty: extraction of properties directly from the NamedTuple returned by ConstructionBase.getproperties

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SatcomCoordinates.AbstractGeocentricPosition Type

julia

AbstractGeocentricPosition{T} <: AbstractPosition{T, 3}

Abstract type representing a position in a geocentric coordinate system.

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SatcomCoordinates.AbstractLocalPosition Type

julia

AbstractLocalPosition{T} <: AbstractPosition{T, 3}

Abstract type representing a position in a local coordinate system.

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SatcomCoordinates.AbstractPointing Type

julia

AbstractPointing{T} <: AbstractSatcomCoordinate{T, 3}

Abstract type representing a pointing direction in 3 dimensions which is backed by fields with shared numbertype T.

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SatcomCoordinates.AbstractPointingOffset Type

julia

AbstractPointingOffset{T} <: AbstractSatcomCoordinate{T, 2}

Abstract type representing a pointing offset between two pointing directions.

Currently only has two concrete subtypes: UVOffset and ThetaPhiOffset.

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SatcomCoordinates.AbstractSatcomCoordinate Type

julia

AbstractSatcomCoordinate{T, N}

General abstract type identifying a coordinate with N dimensions and an underlying number type T. The number type T is not necessarily the type of the fields in the type instance, but their underlying real type (this is only different for fields whose types are Unitful quantities, where numbertype(::Quantity{T}) where T = T).

Note

The term coordinate is used here in a loose sense, identifying both position in space as well as pointing directions

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SatcomCoordinates.AbstractTopocentricPosition Type

julia

AbstractTopocentricPosition{T} <: AbstractPosition{T, 3}

Abstract type representing a position in a topocentric coordinate system.

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SatcomCoordinates.AngularPointing Type

julia

AngularPointing{T}

Abstract type representing a pointing direction identified by two angles in degrees, represented with fields of types Deg{T}.

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SatcomCoordinates.AzEl Type

julia

AzEl{T} <: AngularPointing{T}

Object specifying a pointing direction in "Elevation/Azimuth" coordinates, defined following the convention used for Azimuth-Elevation-Range (AER) coordinates used by MATLAB and by this package.

This represents the azimuth/elevation definition often used for describing pointing from a user terminal on ground towards a satellite. They are very similar to the ElOverAz definition but with a rotation of the underlying CRS such that elevation is 90° in the direction of the +Z axis and azimuth is computed on the XY plane from the +Y axis towards the +X axis.

Assuming u, v, and w to be direction cosines of the pointing versor ̂p, their relation with the El and Az angles is:

u = cos(El) * sin(Az)
v = cos(El) * cos(Az)
w = sin(El)

Fields

az::Deg{T}: The azimuth angle in degrees, constrained to be in the [-180°, 180°] range.
el::Deg{T}: The elevation angle in degrees, constrained to be in the [-90°, 90°] range.

Note

The fields of AzEl objects can also be accessed via getproperty using the azimuth and elevation aliases.

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SatcomCoordinates.AzElDistance Type

julia

const AzElDistance{T} = GeneralizedSpherical{AzEl, T}

Type representing a position w.r.t. a local CRS in Azimuth, Elevation and Range coordinates. The difference between AzElDistance and AER is that AER is a always referred to the ENU CRS, while AzElDistance is for a generic local CRS.

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SatcomCoordinates.AzOverEl Type

julia

AzOverEl{T} <: AngularPointing{T}

Object specifying a pointing direction in "Azimuth over Elevation" coordinates, which specify the elevation and azimuth angles that needs to be fed to an azimuth-over-elevation positioner for pointing to a target towards the pointing direction ̂p.

Following the convention used in most Antenna-related literature, the elevation and azimuth are 0° in the direction of the +Z axis of the reference frame.

Assuming u, v, and w to be direction cosines of the pointing versor ̂p, their relation with the Az and El angles is:

u = -sin(Az)
v = cos(Az) * sin(El)
w = cos(Az) * cos(El)

Note

The equations above are used to represent the "Azimuth over Elevation" coordinates in GRASP. Some textbooks, however, use the opposite convention, meaning that the same equations (with a possible flip in the az/u sign) are used to describe an "Elevation over Azimuth" coordinate system. This is for example the case in the book "Theory and Practice of Modern Antenna Range Measurements" by Clive Parini et al.

Properties

az::Deg{T}: The azimuth angle in degrees, constrained to be in the [-180°, 180°] range.
el::Deg{T}: The elevation angle in degrees, constrained to be in the [-90°, 90°] range.

Note

The fields of AzOverEl objects can also be accessed via getproperty using the azimuth and elevation aliases.

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SatcomCoordinates.BasicCRSTransform Type

julia

BasicCRSTransform{T, R <: Union{CRSRotation{T}, Identity}, O <: AbstractPosition{T, 3}} <: AbstractCRSTransform{T}

A type representing a basic transformation (rotation + translation).

Fields:

rotation::R: The rotation of the transformation.
origin::O: The origin of the transformation.

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SatcomCoordinates.CRSRotation Type

julia

CRSRotation{T, R <: StaticMatrix{T, 3, 3}} <: AbstractCRSRotation{T}

A type representing a basic rotation of a coordinate system.

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SatcomCoordinates.ECEF Type

julia

struct ECEF{T} <: AbstractGeocentricPosition{T}

Represents a position in the Earth-Centered, Earth-Fixed (ECEF) coordinate system (or generically for other planets, Ellipsoid-Centered, Ellipsoid-Fixed).

Properties

x::Met{T}: X-coordinate in meters
y::Met{T}: Y-coordinate in meters
z::Met{T}: Z-coordinate in meters

Basic Constructors

ECEF(x::ValidDistance, y::ValidDistance, z::ValidDistance)

ValidDistance is either a Real Number, or a subtype of Unitful.Length.

If of the provided argument is NaN, the returned ECEF object will contain NaN for all fields.

Fallback constructors

All subtypes of P <: AbstractSatcomCoordinate can also be constructed using a Tuple or SVector as input, which will be splatted into the standard constructor for P

SatcomCoordinates.jl ​

SatcomCoordinates.jl