What is a S-57 file?
A file with .000 extension is a type of electronic navigational chart (ENC), standardized by International Hydrographic Organisation (IHO), that contains vector format data based on the S-57 object model. It contains navigational information such as sea depth, soundings, contours, and other information. All this data is available inside the file in a vector format and is totally independent of how it is displayed by S57 readers. S57 files can be opened using applications such as ESRI ArcGIS, OpenCPN, and APIs such as GDAL.
S-57 File Format
The S-57 model defines hydrographic information using a combination of descriptive and spatial characteristics. It defines the characteristics in terms of objects categorized as a feature and as a spatial part. The descriptive attributes of an object are represented by the feature part and it doesn’t contain any information about the geometry of the object. The spatial part contains the geometry of type vector and may have additional descriptive attributes. A single S-57 data does not exceed 5 Megabytes. ENC charts are usually created from survey data and objects databases, or digitised from a paper or raster chart.
S-57 Features and Attributes
A single S-57 file may contain more than 100 layers. Features in an S-57 file are assigned to a layer based on the name of the object class (OBJL). Each feature type in an S-57 file has a predefined set of attributes as defined by the S-57 standard. These are short names that can be related to longer, more meaningful names using the S-57 object/attribute catalog.
For example, airport (AIRARE) object class can have the AIRARE, CATAIR, CONDTN, CONVIS, NOBJNM, OBJNAM, STATUS, INFORM, NINFOM, NTXTDS, PICREP, SCAMAX, SCAMIN, TXTDSC, RECDAT, RECIND, SORDAT, and SORIND attributes. The more meaningful names of these short names can be found in the S-57 document or the S-57 object/attribute catalog.
