What is a 3D file?
A file with .3d extension is a GIS file that contains data about the cave system that can be visualized with the Survex software. It is created with all the information related to cave systems that can be used for rendering this geographic information file using software such as Aven. Survex is a free open source software used for mapping caves and can be run on a variety of platforms such as macOS, Linux, and Microsoft Windows.
3D GIS File Format - More Inforamtion
The Survex 3D GIS files are in Survex 3D File Format whose file format specifications are available for developer’s reference. These specifications have been used successfully to read the Survex 3D GIS file format.
Survex 3D File Header
The Survex 3D file header consits of the following fields.
- File ID: It is the string “Survex 3D Image File” followed by a linefeed (decimal 10, hex 0a).
- File Format Version: This decribes the file format version. The current version is 8 and that is why this field has value “v8”. Any future releases of the file format will be “v9”, “v10”, etc.
- Associated String MetaData: This must appear in the order specified in the document and should follow the order.
- Coordinate system: PROJ4 string describing the coordinate system in use.
- Timestamp: A string consisting of an ‘@’ followed by a count of seconds since the start of 1970 in UTC (“Unix time_t”) as a string (for example: “@1371300355”), followed by a linefeed. This is intended to be the time the file was generated, rather than the time the survey data was collected.
- File-wide flags: a single byte. If bit 7 is set, this is an extended elevation. All other bits are reserved - set them to 0 when writing, and ignore them when reading.