What action should you take if the coordinate system info of a newly added shapefile is 'Unknown'?

When the coordinate system information of a newly added shapefile is labeled as 'Unknown', the best first step is to define the coordinate system of the data. This is important because having a defined coordinate system allows the GIS software to interpret the spatial data correctly, ensuring that it aligns properly with other datasets that have known coordinate systems.

By defining the coordinate system, you provide essential context for how the spatial data should be understood and used within your GIS projects. Once the coordinate system is set, it enables the data to be visualized accurately and allows for meaningful analysis, facilitating integration with other datasets that have a known coordinate reference.

In contrast, applying a geographic transformation or projecting the data before defining the coordinate system could lead to inaccuracies or misinterpretations of the dataset. Additionally, using projection on the fly is typically a display-only operation that doesn't change the underlying spatial reference of the data; without knowing the correct coordinate system, this approach would not resolve issues arising from the unknown spatial reference.