Library

Documentation for SatelliteToolboxGravityModels.jl.

SatelliteToolboxGravityModels.fetch_icgem_file — Method

fetch_icgem_file(url::AbstractString; kwargs...) -> String
fetch_icgem_file(model::Symbol; kwargs...) -> String

Fetch a ICGEM file from the url and return its file path to be parsed with the function GravityModels.load. If the file already exists, it will not be re-downloaded unless the keyword force = true is passed.

A symbol can be passed instead the URL to fetch pre-configured gravity field models. The supported values are:

:EGM96: Earth Gravitational Model from 1996.
:EGM2008: Earth Gravitational Model from 2008.
:JGM2: Joint Gravity Model 2.
:JGM3: Joint Gravity Model 3.

Examples

julia> fetch_icgem_file(:EGM96)
[ Info: Downloading the ICGEM file 'EGM96.gfc' from 'http://icgem.gfz-potsdam.de/getmodel/gfc/971b0a3b49a497910aad23cd85e066d4cd9af0aeafe7ce6301a696bed8570be3/EGM96.gfc'...
"/Users/ronan.arraes/.julia/scratchspaces/bd9e9728-6f7b-4d28-9e50-c765cb1b7c8c/icgem/EGM96.gfc"

julia> fetch_icgem_file(:EGM96)
"/Users/ronan.arraes/.julia/scratchspaces/bd9e9728-6f7b-4d28-9e50-c765cb1b7c8c/icgem/EGM96.gfc"

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SatelliteToolboxGravityModels.icgem_coefficients — Method

icgem_coefficients(model::IcgemFile{T}, degree::Int, order::Int, time::Union{Number, DateTime}) where T<:Number -> T, T

Compute the ICGEM coefficients (Clm and Slm) of the model for the specified degree and order in the instant time.

time can be expressed using a DateTime object or the number of ellapsed seconds from J2000.0 epoch (2000-01-01T12:00:00.000).

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SatelliteToolboxGravityModels.parse_icgem — Function

parse_icgem(filename::AbstractString, T::DataType = Float64) -> IcgemFile

Parse the ICGEM file filename using the data type T.

Note

T is converted to float to obtain the output type.

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SatelliteToolboxGravityModels.GravityModels.AbstractGravityModel — Type

abstract type AbstractGravityModel{T<:Number}

Abstract data type of all gravity models.

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SatelliteToolboxGravityModels.GravityModels.coefficient_norm — Function

coefficient_norm(model::AbstractGravityModel) where T<:Number -> Symbol

Return the normalization we must use in the spherical harmonics when computing the Legendre associated functions. The accepted values are:

:full: Use full normalization.
:schmidt: Use Schmidt quasi-normalization.
:unnormalized: Do not perform normalization.

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SatelliteToolboxGravityModels.GravityModels.coefficients — Function

coefficients(model::AbstractGravityModel{T}, degree::Int, order::Int[, time::Union{Number, DateTime}]) where T<:Number -> T, T

Return the Clm and Slm coefficients of the gravity model for the specified degree, order, and time. If the latter argument is omitted, the J2000.0 epoch is used.

time can be expressed using a DateTime object or the number of ellapsed seconds from J2000.0 epoch.

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SatelliteToolboxGravityModels.GravityModels.gravitational_acceleration — Method

gravitational_acceleration(model::AbstractGravityModel{Number}, r::AbstractVector{Number}[, time::Union{Number, DateTime}]; kwargs...) -> NTuple{3, RT}

Compute the gravitational acceleration [m / s²] represented in ITRF using the model in the position r [m], also represented in ITRF, at instant time. If the latter argument is omitted, the J2000.0 epoch is used (2000-01-01T12:00:00).

time can be expressed using a DateTime object or the number of ellapsed seconds from J2000.0 epoch.

Note

Gravitational acceleration is the acceleration caused by the central body mass only, i.e., without considering the centrifugal potential.

Keywords

max_degree::Int: Maximum degree used in the spherical harmonics when computing the gravitational field derivative. If it is higher than the available number of coefficients in the model, it will be clamped. If it is lower than 0, it will be set to the maximum degree available. (Default = -1)
max_order::Int: Maximum order used in the spherical harmonics when computing the gravitational field derivative. If it is higher than max_degree, it will be clamped. If it is lower than 0, it will be set to the same value as max_degree. (Default = -1)
P::Union{Nothing, AbstractMatrix}: An optional matrix that must contain at least max_degree + 1 × max_degree + 1 real numbers that will be used to store the Legendre coefficients, reducing the allocations. If it is nothing, the matrix will be created when calling the function. (Default = nothing)
dP::Union{Nothing, AbstractMatrix}: An optional matrix that must contain at least max_degree + 1 × max_degree + 1 real numbers that will be used to store the Legendre derivative coefficients, reducing the allocations. If it is nothing, the matrix will be created when calling the function. (Default = nothing)

Returns

RT: The derivative of the gravitational field w.r.t. the radius (∂U/∂r).
RT: The derivative of the gravitational field w.r.t. the geocentric latitude (∂U/∂ϕ).
RT: The derivative of the gravitational field w.r.t. the longitude (∂U/∂λ).

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SatelliteToolboxGravityModels.GravityModels.gravitational_field_derivative — Method

gravitational_field_derivative(model::AbstractGravityModel{Number}, r::AbstractVector{Number}[, time::Union{Number, DateTime}]; kwargs...) -> NTuple{3, RT}

Compute the gravitational field derivative [SI] with respect to the spherical coordinates (∂U/∂r, ∂U/∂ϕ, ∂U/∂λ) using the model in the position r [m], represented in ITRF, at instant time. If the latter argument is omitted, the J2000.0 epoch is used.

time can be expressed using a DateTime object or the number of ellapsed seconds from J2000.0 epoch.

Info

In this case, ϕ is the geocentric latitude and λ is the longitude.

Keywords

max_degree::Int: Maximum degree used in the spherical harmonics when computing the gravitational field derivative. If it is higher than the available number of coefficients in the model, it will be clamped. If it is lower than 0, it will be set to the maximum degree available. (Default = -1)
max_order::Int: Maximum order used in the spherical harmonics when computing the gravitational field derivative. If it is higher than max_degree, it will be clamped. If it is lower than 0, it will be set to the same value as max_degree. (Default = -1)
P::Union{Nothing, AbstractMatrix}: An optional matrix that must contain at least max_degree + 1 × max_degree + 1 real numbers that will be used to store the Legendre coefficients, reducing the allocations. If it is nothing, the matrix will be created when calling the function. (Default = nothing)
dP::Union{Nothing, AbstractMatrix}: An optional matrix that must contain at least max_degree + 1 × max_degree + 1 real numbers that will be used to store the Legendre derivative coefficients, reducing the allocations. If it is nothing, the matrix will be created when calling the function. (Default = nothing)

Returns

RT: The derivative of the gravitational field w.r.t. the radius (∂U/∂r).
RT: The derivative of the gravitational field w.r.t. the geocentric latitude (∂U/∂ϕ).
RT: The derivative of the gravitational field w.r.t. the longitude (∂U/∂λ).

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SatelliteToolboxGravityModels.GravityModels.gravity_acceleration — Method

gravity_acceleration(model::AbstractGravityModel{Number}, r::AbstractVector{Number}[, time::Union{Number, DataTime}]; kwargs...) -> NTuple{3, RT}

Compute the gravity acceleration [m / s²] represented in ITRF using the model in the position r [m], also represented in ITRF, at instant time. If the latter argument is omitted, the J2000.0 epoch is used.

time can be expressed using a DateTime object or the number of ellapsed seconds from J2000.0 epoch.

Note

Gravity acceleration is the compound acceleration caused by the central body mass and the centrifugal force due to the planet's rotation.

Keywords

max_degree::Int: Maximum degree used in the spherical harmonics when computing the gravitational field derivative. If it is higher than the available number of coefficients in the model, it will be clamped. If it is lower than 0, it will be set to the maximum degree available. (Default = -1)
max_order::Int: Maximum order used in the spherical harmonics when computing the gravitational field derivative. If it is higher than max_degree, it will be clamped. If it is lower than 0, it will be set to the same value as max_degree. (Default = -1)
P::Union{Nothing, AbstractMatrix}: An optional matrix that must contain at least max_degree + 1 × max_degree + 1 real numbers that will be used to store the Legendre coefficients, reducing the allocations. If it is nothing, the matrix will be created when calling the function. (Default = nothing)
dP::Union{Nothing, AbstractMatrix}: An optional matrix that must contain at least max_degree + 1 × max_degree + 1 real numbers that will be used to store the Legendre derivative coefficients, reducing the allocations. If it is nothing, the matrix will be created when calling the function. (Default = nothing)

Returns

RT: The derivative of the gravitational field w.r.t. the radius (∂U/∂r).
RT: The derivative of the gravitational field w.r.t. the geocentric latitude (∂U/∂ϕ).
RT: The derivative of the gravitational field w.r.t. the longitude (∂U/∂λ).

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SatelliteToolboxGravityModels.GravityModels.gravity_constant — Function

gravity_constant(model::AbstractGravityModel{T}) where T<:Number -> T

Return the gravity constant [m³ / s²] for the gravity model.

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SatelliteToolboxGravityModels.GravityModels.load — Function

load(::Type{T}, args...; kwargs...) where T<:AbstractGravityModel -> T

Load a gravity model of type T using the arguments args... and keywords kwargs....

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SatelliteToolboxGravityModels.GravityModels.maximum_degree — Function

maximum_degree(model::AbstractGravityModel) -> Int

Return the maximum degree of the gravity model.

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SatelliteToolboxGravityModels.GravityModels.radius — Function

radius(model::AbstractGravityModel{T}) where T<:Number -> T

Return the radius [m] for the gravity model.

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