From 3c77b1dc14538cfdd5d32474193271fff183cb33 Mon Sep 17 00:00:00 2001 From: Tim Schaub Date: Tue, 14 May 2013 22:23:15 -0600 Subject: [PATCH] Removing crs This makes all GeoJSON objects Geographic/WGS84 in sensible longitude, latitude order. --- middle.mkd | 64 ++++++++---------------------------------------------- 1 file changed, 9 insertions(+), 55 deletions(-) diff --git a/middle.mkd b/middle.mkd index 2cc8873..1d7326f 100644 --- a/middle.mkd +++ b/middle.mkd @@ -195,10 +195,6 @@ referred to as the GeoJSON object in this document. value - additional rules apply, then these are stated in the following sections where each type is further defined. -* A GeoJSON object MAY have an optional "crsURN" member. If it is present, - the value of it MUST be a valid coordinate reference system reference - (see "[3. Coordinate Reference System (CRS) Reference](rfc.section.3)"). - * A GeoJSON object MAY have a "bbox" member. If it is present, the value of it MUST be a bounding box array (see "4. Bounding Box"). @@ -227,14 +223,9 @@ member of a geometry object is composed of either: * or a multidimensional array of positions (MultiPolygon). A position is represented by an array of numbers. There MUST be two -or more elements. The order of elements must follow x, y, z order -that is: - -* easting, northing, altitude for coordinates in a projected coordinate - reference system, or - -* longitude, latitude, altitude for coordinates in a geographic - coordinate reference system. +or more elements. The first two elements will be World Geodedic System +(WGS 84) longitude and latitude. The optional third element will be +altitude in meters. Any number of additional elements are allowed -- interpretation and meaning of additional elements is beyond the scope of this @@ -322,45 +313,10 @@ element in the array is a feature object as defined above. # Coordinate Reference System (CRS) -The coordinate reference system of a GeoJSON object is determined -by the value of its "crsURN" member (referred to as the CRS reference -below). If an object has no crsURN member, then its parent or -grandparent object's crsURN member may be acquired. If no crsURN member -can be so acquired, the default CRS shall apply to the GeoJSON object. - -* The default CRS is a geographic coordinate reference system, using - the WGS84 datum, and with longitude and latitude units of decimal - degrees. Note-sdrees: FIXME mail from Adrian Custer states as **the - two GeoJSON crs** CRS84 (an axis-flipped WGS84) and CRSGoogle - (EPGS:3857). So is this really WGS84 mentioned as default? - -* The value of a member named "crsURN" must be a string (referred to - as the CRS reference below) or JSON null. If the value of "crsURN" is - null, no CRS can be assumed. Note-sdrees: FIXME or default CRS as - when crsURN member is left out? It is optional anyway. - -* The crsURN member SHOULD be on the top-level GeoJSON object in the - following canonical hierarchical ordering, i.e. if present on a - feature collection, else if present on a feature, else on a geometry - and MUST NOT be repeated or overridden on children or - grandchildren of the object. - -* The referenced CRS SHALL NOT change coordinate ordering (see - "2.1.1 Position"). - -Note-sdrees: The name has been changed from crs to crsURN to not -irritate consumers that expect the crs object as of version 1.0 in the -community spec. - -If present the CRS reference MUST indicate a coordinate reference -system by name. In this case, the value of it MUST be a string -identifying a coordinate reference system. OGC CRS URNs such as -"urn\:ogc:def:crs:OGC:1.3:CRS84" SHALL be preferred over legacy -identifiers such as "EPSG:4326": - - "crsURN": "urn:ogc:def:crs:OGC:1.3:CRS84" - -For the format of a valid URN cf. [RFC5165]. +The coordinate reference system of a GeoJSON object is a geographic +coordinate reference system, using the World Geodedic System 1984 +(WGS 84) datum, and with longitude and latitude units of decimal +degrees. # Bounding Box @@ -369,10 +325,8 @@ on the coordinate range for geometries, features, or feature collections. The value of the bbox member MUST be an array of length 2*n where n is the number of dimensions represented in the contained geometries, with the lowest values for all axes followed by the highest -values. The axes order of a bbox follows the axes order of geometries. -In addition, the coordinate reference system for the bbox is assumed to -match the coordinate reference system of the GeoJSON object of which it -is a member. +values. The axes order of a bbox follows the axes order of geometries +(longitude, latitude). Example of a bbox member on a feature: