Creating and registering a custom dataset for detailed information
Custom objects are a flexible plugin mechanism in Carmenta Engine for integrating customized operations in a regular map configuration. More functionality is added in new Carmenta Engine versions to make this integration more seamless compared to the built-in objects. In this guide, we will focus on the custom dataset use case, for retrieving a customized DataSetInfo, and dynamically instantiating the dataset based on a file on disk.
Carmenta Engine as a geodata processor
In Carmenta Engine we define data flows by linking operators together. An operator reads features from its input, processes or manipulates those features and pass the result to the next operator. In the typical case, operators are added and configured in a configuration file and calls are managed by the map view without direct user interaction with the operators.
But in some cases a more custom approach is necessary and the application need to access the processed features directly in code. For example, the application may want to display information produced by the operators or an external component (or service) may want to use the result as input. In this article, we will explain how to approach such use-case.
Geographical Coordinates in a Carmenta Engine workflow
Geographical data and map views are defined in a Coordinate Reference Systems (CRS). There are many different coordinate systems, which can be used for different purposes. It is for example very common to use a Mercator coordinate projection for visualization of worldwide data on a map. In contrast, Mercator is not recommended for calculations or data storage, because of risk for lack of precision, especially near the poles.
An application often needs to handle geodata in different CRSs or visualize it in another CRS than the CRS of the data source. This means that the data needs to be reprojected at some point. These projections can both affect performance and cause a loss of accuracy if they are not performed efficiently.
Carmenta Engine has in-depth support for efficient coordinate transformations. In this article, we will describe how geographical coordinates are generally handled in the Carmenta Engine workflow, as well as go into some more advanced use cases and best practices.