Which strategy can help reduce the file size of a tile package for a national scale application?

Reducing the detail by limiting the number of colors is an effective strategy for decreasing the file size of a tile package, especially for a national scale application. Tile packages are often used to serve map tiles efficiently, and their size directly impacts performance and load times. By simplifying the color palette, you can significantly reduce the amount of data that needs to be stored and transferred.

This technique minimizes the complexity of the tile images, which can contribute to a smaller file size while still maintaining sufficient visual fidelity for users. A limited color range often results in less data being processed and stored in each tile, making the overall package more manageable.

In contrast, including more datasets or opting for more complex datasets would likely increase the file size, as additional data requires more storage space. Applying heavy detailing throughout would also lead to larger file sizes due to the increase in information and visual intricacies captured in each tile. Therefore, limiting the number of colors stands out as the most effective approach for file size reduction in this scenario.