IGEO7 - Index functions and neighbor traversal in the IGEO7/Z7 DGGS

This is a work-in-progress to explore the possibility of neighbor traversal in the IGEO7/Z7. Z7 is an indexing system for the IGEO7 aperture 7 hexagonal discrete global grid DGGRID/Sahr Kmoch et al. (2025). It is based on the Generalized Balanced Ternary (GBT) numeral system described in Lucas, Gibson (1982), van Roessel (1988), Sahr (2019), and Wikipedia (2025).

Usage Example

using IGEO7

# Create an index from a string
idx = z7string_to_index("0103")

# Get resolution of the cell
res = get_resolution(idx) # returns 2

# Find all 6 neighbors
neighbors = get_neighbours(idx)
for n in neighbors
    if n.raw != typemax(UInt64)
        println(index_to_z7string(n))
    end
end

Rotation Pattern

For reference purposes a rendering of three hierarchies of alternating GBT rotation is included (CW, CCW, CW).

Acknowledgements

2019-2026 Kevin Sahr sahrk@sou.edu DGGRID https://github.com/sahrk/DGGRID/

https://github.com/wrenoud/Z7/

• 2025-2026 Javier Jimenez Shaw https://github.com/jjimenezshaw
• 2025-2026 Weston James Renoud https://github.com/wrenoud