I am working with US National Grid (USNG) for the whole United States, containing 1 km by 1km polygons which diverge around UTM boundaries. I need to assign the values of a raster in GRID format which also has a 1 km x 1 km resolution, for each respective USNG square. They do not exactly match up. I have tried several methods, and need to determine the best method to accurately get a representation of the raster value for each polygon. I am looking for a solution in ArcMap or ArcGIS Pro. The methods I have tried are:
Spatial Join - convert the Raster cells into point features, and perform a spatial join with the USNG. Pros/Cons: relies on only the closest raster cell.
Zonal Statistics as Table - Calculate the mean raster value for each zone (which are USNG grids). Pros/Cons: can average several raster cells which overlap the grid square, but not as good for cases when one cell covers the majority of the grid square.
Snap Raster - convert the USNG into a raster format(?), and use Snap Raster to align the two. Or some variation of this, where I am aligning the two layers together.
Each approach has advantages and limitations. Is there an additional method I have not considered? Do you have any input on how to best achieve the goal of assigning raster values to a grid, for a very large dataset?