# About bounding volume defined by oriented Box

Hi All,

I need a little clarification about oriended box in TileSet definition.

“box” : {
“type” : “array”,
“description” : “An array of 12 numbers that define an oriented bounding box in WGS84 coordinates.
The first three elements define the x, y, and z values for the center of the box.
The next three elements (with indices 3, 4, and 5) define the x axis direction and length.
The next three elements (indices 6, 7, and 8) define the y axis direction and length.
The last three elements (indices 9, 10, and 11) define the z axis direction and length.”,
“items” : {
“type” : “number”
},
“minItems” : 12,
“maxItems” : 12
},

``

I’m wondering what WGS84 coordinates does exactly mean :

• Geographic/WGS84 : X & Y are Lon/Lat in radians and Z is a value in meters,

• ECEF/WGS84 : X, Y and Z are ECEF coordinates in meters.

• something else ?

Does anyone here can clarify ?

KR,

Fred.

Hi,
after looking on how 3D TileSets are loaded and interpreted in Cesium, I think that Box coordinates have to be ECEF (Cartesian) coordinates.

As I tile my input dataset using cartographic rectangles, corresponding oriented boxes in ECEF system are not easy to compute (and are probably not really boxes).

I will try to tile in geographic coordinates and the use the region tag in tileset.json.

Br,

Fred.

Hi Frédéric,

To confirm, yes ECEF and WGS84 coordinates are the same. For more on WGS84, see http://earth-info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf

I agree that using the region property sounds like the best approach for you.

Patrick

Hi Patick,

I now use regions and it works fine, I was able to display my first 3D city few days ago :

700.000 buildings - B3DM tiles are generated on the fly.

3D Tiles is great.

Kr,

Fred.