A good laugh at staring at terrio "source code" (not sure the term is adequate. perhaps "LLM output"): a data structure called Terrain313 ( https://github.com/opengeos/terrio/blob/40751a32a0707c87fa13eb434dc42025dc25b299/crates/terrio/src/ops/dem.rs#L550 ). Why 313 ... ? Because it was ported from GDAL 3.13 apparently 😂 This made my day. Thanks LLMs