What happens if a raster layer does not have a defined projection?

When a raster layer does not have a defined projection, it significantly impacts the accuracy of its use in analyses. A projection provides a way to translate three-dimensional points on the earth's surface to a two-dimensional representation, ensuring that spatial relationships are accurately maintained. Without a defined projection, the raster's location and scale on the earth are uncertain, which can lead to misalignments when overlaid with other spatial data that do have defined projections.

In analyses, such as overlaying different datasets, conducting spatial queries, or performing statistical evaluations, the lack of a proper spatial reference can lead to incorrect results. With no projection, the system cannot determine how to interpret the raster data accurately regarding geographic location, resulting in potential errors in analysis outcomes.

The impact of a raster layer lacking defined projection necessitates careful consideration before use in any spatial analysis, emphasizing the need for proper georeferencing and the significance of projections in GIS work.