Which of the following is an example of unreferenced data?

Unreferenced data refers to data that lacks a spatial reference system or geographic context. In the context of Geographic Information Systems (GIS), this means that the data does not have a specific location or coordinate system attached to it, which makes it challenging to analyze spatially or integrate with other geographic datasets.

PDF plans serve as an example of unreferenced data because they can contain graphical information like maps or plans, but without spatial reference, such as coordinates or projection information. The contents within a PDF document may represent features or locations, but because they are embedded within the document and not linked to a spatial reference framework, the data cannot be easily used for geographic analysis or combined with other spatial datasets.

On the other hand, digital shapefiles, survey data, and geocoded datasets all possess inherent spatial references. Shapefiles are designed to store geographic features along with their attributes while being tied to a coordinate system. Survey data typically includes measurements and locations based on established geographic markers, and geocoded datasets explicitly link data points to geographic coordinates, thus facilitating spatial analysis. Therefore, these options do not represent unreferenced data due to their strong association with spatial context.