Interface

SpaceDataModel.jl provides a set of abstractions and generic functions that can be extended by users to create custom implementations. This page documents these interfaces and provides examples of how to use them.

References

• DataAPI.jl: A data-focused namespace for packages to share functions

Coordinate Systems

The package exports three key components for coordinate system handling:

• AbstractCoordinateSystem: Base abstract type for all coordinate system implementations
• AbstractCoordinateVector: Base abstract type to represent coordinates in a coordinate systems
• getcsys: Function to retrieve the coordinate system from an object

There are two main approaches to implementing coordinate vectors and their associated systems:

Approach 1: Explicit Coordinate System Field

Store the coordinate system directly as a field in the vector type:

# Define a coordinate system
struct GEO <: AbstractCoordinateSystem end

# Define a vector with an explicit coordinate system field
struct CoordinateVector{D, T} <: AbstractCoordinateVector
    data::D
    csys::T
end

# Implementation of getcsys simply returns the stored field
getcsys(x::CoordinateVector) = x.csys

Approach 2: Implicit Coordinate System

Associate a specific coordinate system with a vector type:

# Define a coordinate system
struct GEO <: AbstractCoordinateSystem end

# Define a vector type specific to a coordinate system
struct GEOVector{D} <: AbstractCoordinateVector
    data::D
end

# Implementation of getcsys returns the appropriate system
getcsys(x::GEOVector) = GEO()

Both approaches are highly efficient and provide equivalent performance due to Julia's type inference system.

Elsewhere

• CoordRefSystems.jl provides conversions between Coordinate Reference Systems (CRS) for cartography use cases.
• Geodesy.jl for working with points in various world and local coordinate systems.
• WCS.jl : Astronomical World Coordinate System library