HexTree

hextree provides tree structures that represent geographic regions with H3 cells.

The primary structures are:

• HexTreeMap: an H3 cell-to-value map.
• HexTreeSet: an H3 cell set for hit-testing.

You can think of HexTreeMap vs. HexTreeSet as HashMap vs. HashSet.

How is this different from HashMap<H3Cell, V>?

The key feature of a hextree is that its keys (H3 cells) are hierarchical. For instance, if you previously inserted an entry for a low-res cell, but later query for a higher-res child cell, the tree returns the value for the lower res cell. Additionally, with compaction, trees can automatically coalesce adjacent high-res cells into their parent cell. For very large regions, the compaction process can continue to lowest resolution cells (res-0), possibly removing millions of redundant cells from the tree. For example, a set of 4,795,661 res-7 cells representing North America coalesces into a 42,383 element HexTreeSet.

A hextree's internal structure exactly matches the semantics of an H3 cell. The root of the tree has 122 resolution-0 nodes, followed by 15 levels of 7-ary nodes. The level of an occupied node, or leaf node, is the same as its corresponding H3 cell resolution.

Features

• serde: support for serialization via serde.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.