@zwaarcontrast/ol-graticule-ngo

The Norwegian Gauss-Krüger strips ("norweg. Gitterstreifen") as German WWII 1:50 000 sheets of Norway print them, for @zwaarcontrast/ol-graticule.

Live demo: https://zwaarcontrast.nl/ol-graticule/ol-graticule-ngo/

Each strip is transverse Mercator with scale 1 on its central meridian, given east of the Oslo meridian (10°43'22.5" E of Greenwich), on the modified Bessel ellipsoid:

| Strip | CRS | Central meridian | Origin | False E / N | Checked on | | ----- | ---------------- | ---------------- | ------ | ------------------- | ---------------------------------------------------------------- | | I | NGO:STRIP_I | 4°40' W of Oslo | 58°N | 200 000 / 100 000 m | B 34-W Fana, B 38 W-O Stavanger | | II | NGO:STRIP_II | 2°20' W of Oslo | 58°N | 400 000 / 100 000 m | E 26 O Trollheimen, E 26 W Stangvik, E 27 W Aura, E 24 W Kvenvär | | III | NGO:STRIP_III | Oslo | 58°N | 600 000 / 100 000 m | H 38 Enningdal | | IV | NGO:STRIP_IV | 2°30' E of Oslo | 64°N | 100 000 / 100 000 m | Jot 18 Hattfjelldal | | V | NGO:STRIP_V | 6°10' E of Oslo | 66°N | 300 000 / 100 000 m | M 6 Torsken | | VI | NGO:STRIP_VI | 10°10' E of Oslo | 68°N | 500 000 / 100 000 m | T 7 Kautokeino | | VII | NGO:STRIP_VII | 14°10' E of Oslo | 68°N | 700 000 / 100 000 m | X 4 Laksfjordvidda | | VIII | NGO:STRIP_VIII | 18°20' E of Oslo | 68°N | 900 000 / 100 000 m | Y 3 Vestertana |

Each sheet's margin names its strip and central meridian. The origins and false co-ordinates are fitted to the grid printed against the graticule; every measured corner matches to within 25 m. The sheets name no ellipsoid or datum; the shift to WGS84 is the NGO 1948 seven-parameter one.

From the EPSG registry: the Oslo meridian (EPSG:8913), the Bessel Modified ellipsoid (EPSG:7005), every central meridian (NGO zones, EPSG:27391-27398), the strip boundaries (extents 1741-1748) and the WGS84 shift (EPSG:1654, 3 m). EPSG's zones put every origin at 58°N with no false co-ordinates; the origins and false co-ordinates here are the German sheets' own, and no published source for them has been found yet.

Usage

import { UniversalGraticule } from '@zwaarcontrast/ol-graticule';
import { createNGOStripGridSystem } from '@zwaarcontrast/ol-graticule-ngo';

map.addLayer(
  new UniversalGraticule({ gridSystem: createNGOStripGridSystem('V') }),
);

createNGOStripGridSystem(strip, options) takes the ProjectedGridSystem options except crs, proj4Def and extent, which the strip fixes. NGO_GRIDS holds every strip keyed by CRS (crs, name, proj4, validityWgs84, createGridSystem()). NGO_STRIPS (strip parameters, proj4 strings and WGS84 validity bands) is also exported ol-free from @zwaarcontrast/ol-graticule-ngo/headless.

Each strip is clipped to a band between the EPSG zone boundaries (the midpoints of adjacent central meridians), over the latitudes of that zone's EPSG area of use (extents 1741-1748): strip V, for instance, runs from 66.15°N to 70.27°N. The sheets do not print strip boundaries, and a sheet near one carries its own strip past it.