REGARDS products geometry

Products geometry

REGARDS use GeoJson format for indexed products. Geometry associated to a product is defined in "geometry" field like here under exemples.

As REGARDS uses GeoJson standard, geometries need to respect GeoJson format as defined in RFC 7946.

Principal rules to generate geometries are :

• External ring of polygones MUST be oriented counterclockwise
• Distance between two successive points cannot be larger than 180°

If those two rules are respected, REGARDS will take your geometry into account and will cut polygons which cross antimeridian into multi polygons to allow catalog research using WGS84.

Valid polygons

{
  "type": "Feature",
  "id": "file_1.txt",
  "ipType": "DATA",
  "geometry": {
    "type": "MultiPolygon",
    "coordinates": [
      [
        [
          [
            -170,
            28
          ],
          [
            -170,
            10
          ],
          [
            -180,
            10
          ],
          [
            -180,
            28
          ],
          [
            -170,
            28
          ]
        ]
      ],
      [
        [
          [
            180,
            28
          ],
          [
            170,
            28
          ],
          [
            170,
            10
          ],
          [
            180,
            10
          ],
          [
            180,
            28
          ]
        ]
      ]
    ]
  },
  "properties": {}
}

Invalid polygon (wrong rotation way)

{
    "type": "Feature",
    "id": "file_1.txt",
    "ipType": "DATA",
    "geometry": {
        "type":"Polygon",
        "coordinates":[[[-50,28],[-50,10],[-20,10],[-120,28],[-50,28]]]
    },
    "properties": {}
}

Invalid polygon crossing antimeridian (distance between two successive points too large and right rotation way)

{
    "type": "Feature",
    "id": "file_1.txt",
    "ipType": "DATA",
    "geometry": {
        "type":"Polygon",
        "coordinates":[[[50,-50],[-20, -50],[-20,10],[50,10],[-50,-50]]]
    },
    "properties": {}
}

REGARDS projects geometry configuration

For each projet of a REGARDS instance, administrator can configure how geometry will be handled with two parameters :

• Projection : Choose between REGARDS handled projections WGS84 (for earth geometries), Mars or Celestial vault.
• handle polar cap polygons : If true, polygons are transformed using a spherical projection and then polygons should respect the previous second rule defined (distance between too consecutive points).

Those two parameters are configurable through admin instance UI during project configuration.