Definition of a grid as a Discrete Global Grid Reference System
Source:R/dggrs_definition.R
dggrs_definition.RdDescribes a grid in the DGGRS definition schema of OGC API - Discrete Global Grid Systems: the hierarchy of grids (solid, refinement ratio, refinement strategy, zone shapes, orientation), the zone identifiers and the order of sub-zones.
Value
A named list with the schema's fields title,
description, dggh, zirs and subZoneOrder.
jsonlite::toJSON(x, auto_unbox = TRUE, pretty = TRUE) writes it as
JSON.
Details
The definition describes the grid as hexify builds it. The zone
identifiers are the strings cell_to_index writes, which carry
their resolution and are unique across all resolutions, and the cell IDs,
which number the cells of one resolution from 1 and are unique only
together with it.
The ISEA3H and ISEA7H definitions registered with OGC (https://www.opengis.net/def/dggrs/OGC/1.0/ISEA7H) are other grids: they convert WGS84 geodetic latitude to authalic latitude before projecting, and place the icosahedron's first vertex at 11.20 degrees E and authalic latitude \(\arctan(\phi)\), where hexify, like DGGRID, reads latitude on the sphere and places it at 11.25 degrees E. A hexify grid is therefore described without an OGC URI.
References
Open Geospatial Consortium. OGC API - Discrete Global Grid Systems - Part 1: Core. OGC 21-038r1. https://docs.ogc.org/is/21-038r1/21-038r1.html
Examples
def <- dggrs_definition(hex_grid(resolution = 5, aperture = 7))
def$dggh$definition$refinementRatio
def$zirs$textZIRS$description