MapGlHurdal

Coordinate Systems

• WGS84 (EPSG:4326)

  • Default for GeoJson files, and implicit for newer versions

  • Coordinate System: Geographic coordinate system (GCS).

  • Units: Degrees of latitude and longitude.

  • Description: WGS84 is a global standard coordinate system used by GPS. Coordinates are expressed in degrees of latitude (north/south) and longitude (east/west), which represent positions on the Earth's surface as if it were a sphere.

  • Use Case: WGS84 is typically used for storing raw geographic coordinates. It is the default in many geographic datasets and is required by standards like GeoJSON.

• Web Mercator (EPSG:3857)

  • Coordinate System: Projected coordinate system (PCS).

  • Units: Meters.

  • Description: Web Mercator projects the Earth’s surface onto a flat, two-dimensional plane using the Mercator projection. Instead of latitude and longitude, it uses x and y coordinates in meters. This projection distorts areas near the poles but preserves angles, making it useful for maps where visualizing shapes and distances (within reasonable latitudes) is more important than size accuracy.

  • Use Case: Web Mercator is commonly used in web mapping applications (e.g., Google Maps, OpenStreetMap, Bing Maps) because it allows for seamless panning and zooming.

• GeoNorge uses UTM (Universal Transverse Mercator)

  • Sone 32N: EPSG:25832 - Dekker det meste av Sør-Norge.

  • Sone 33N: EPSG:25833 - Dekker deler av Øst-Norge.

  • Sone 35N: EPSG:25835 - Brukes for Øst-Finnmark.

Conversions

• proj4js

• ogr2ogr from GDAL

  • This one won't work properly for SOSI-type files (which is what Geonorge.no exports everything from, I think, and so their files contain lot's of custom properties)

Formats

GeoJson can be converted to THREE.js polygons.

GeoJson-valiator

GeoNorge.no

Mapdata sets. Add to downloads, and proceed to "checkout". Select:

• Kartdata N50 Kartdata

  • Geografisk område: "Hurdal"

  • Projeksjon: "Utm sone 32" (Or UTM33 for further north i Norway)

  • Format: "GML"

  • See scripts/geojson_howto.md for extracting geojson files from gml-files.

• DEM (Digital Elevation Model)

  • "Digital TerrengModell 10" DTM10UTM32

  • See scripts/DTM10_howto.md for merging and cropping the geotiff