Architecture

Transformo is built using a pipeline architecture that revolves around three types of components: DataSources, Operators and Presenters.

A number of DataSources can be fed to a series of Operators, that defines the desired transformation to estimate parameters for, and the resulting parameters and related statistics are returned using Presenters. The combination of DataSources, Operators and Presenters are called a "Pipeline". The figure below give a schematic overview of the concept.

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flowchart TD

    subgraph Source Coordinates
        S_1[DataSource 1] --> S_C
        S_3[...] --> S_C
        S_N[DataSource N] --> S_C
    end
        S_C[SourceDataSource] --> O_1

    subgraph Target Coordinates
        T_1[DataSource 1] --> T_C
        T_3[...] --> T_C
        T_N[DataSource N] --> T_C
    end
        T_C[TargetDataSource] --> O_1

    subgraph Transformation
        O_1[Operator 1] --> O_2[Operator 2]
        O_2 --> O_3[...]
        O_3 --> O_N[Operator N]
    end

    subgraph Results
        O_N --> P_1[Presenter 1]
        O_N --> P_2[Presenter 2]
        O_N --> P_3[...]
        O_N --> P_N[Presenter N]
    end

DataSources gathers sets of source and target coordinates and assembles them in a standardized internal form and Presenters presents the derived transformation model and related statistics in standardized formats.

The Operators derive parameters for selected transformation techniques, for instance a Helmert transformation. In case of several chained operators the later steps are presented with the residuals of the earlier transformation estimate for which the current operator can attempt to reduce even further using a different transformation technique.

DataSources

DataSources consumes data from a single data source and provide it on a standardized form. The following information can be read with a datasource:

1. Station name
2. Coordinate tuple (x,y,z)
3. Uncertainty estimate of the coordinate (standard deviation)
4. Weight (>= 0.0)
5. Timestamp

Source and target coordinate data is handled by different datasource instances. At least one datasource is needed for both source and target data sources but more than one can be supplied for each.

Presenters

Presenters deliver the resulting estimated transformation parameters in sensible formats. Parameters for a Helmert transformation might be presented as a PROJ-string, a WKT2 description and a simple text representation. A grid based transformation might result in a GTG file or a more complex transformation involving several steps could be returned as a PROJ pipeline.

Presenters aren't limited to only presenting the estimated parameters. A presenter can also return intermediate results, residuals and various other statistics relevant to the transformation at hand.

Operators

Operators are essential components in the Transformo pipeline. All operators have the ability to manipulate coordinates, generally in the sense of a geodetic transformation. In addition operators can implement a method to derive parameters for said coordinate operation. Most operators do, but not all.

So, operators have two principal modes of operation:

1. Coordinate operations, as defined in the ISO 19111 terminology
2. Estimating parameters for the coordinate operations

The abilities of a operator are determined by the methods that enheriting classes implement. All Operator's must implement the forward method and they can implement the estimate and inverse methods. If only the forward method is implemented the operator will exist as a coordinate operation that can't estimate parameters.