Feature Representation

In addition to the generic FME feature attributes that FME Workbench adds to all features (see About Feature Type Attributes), this format also adds format-specific attributes (Format Attributes).

Attribute Name	Contents
hyd93_type	The FME generic geometric type of this entity. Range: hyd93_point, hyd93_no_geom

DATA RECORD

The data record file contains a variable number of data records. Each record is output as a feature of the feature type RECORD. This feature will always have a hyd93_geometry value of hyd93_point.

Each data record represents the same in binary as in ASCII, except the survey id, which occurs in the ASCII HYD93 data record, is absent in HYD93 Binary Records.

Format Conventions:

1. Unknown or unused values are filled with 9's.
2. All Bathymetric Sounding (non-feature) data records include a known depth value, a value type of 0 (actual depth) and a cartographic code of 711 (Sounding in meters and tenths).
3. Negative depth values indicate elevations.
4. Hydrographic Feature records with non-zero Value Type may or may not have a known (non 9's) value.
5. Hydrographic Features which are "Line Features" do not include depths. Instead the depth value fields are used for the sequence numbers each record along the line feature (1...n).
6. All decimal points are implied (e.g., 1234 in 10ths of units means 123.4)
7. Leading zeros and blanks are equivalent.
   

Fields can be of type integer, real or character. Fields that represent whole numbers are integers. Fields that contain a decimal component are real (the decimal point is always implied), and fields that are alphanumeric are character.

The second, third and fourth fields of each line in an ASCII HYD93 file indicate latitude, longitude, and depth value, respectively. Similarly, the first three fields of each record of a binary file indicate latitude, longitude, and depth value. Latitude and longitude are given in millionths of degrees, and depth values are given in tenths of meters.

The attributes of an ASCII record feature are described in the following table.

Attribute	Character Offset	Type	Description
hyd93_survey_identifier	1-8	char	Identifier supplied by the contributing organization, else given by NGDC in a manner which represents the data. Identical to that in the header record.
hyd93_value_type_code	34	int	Defines depth type. 0 - Known depth (or elevation) 1 - Submerged (below water level) 2 - Awash (about water level) 3 - Visible (above water level)
hyd93_cartographic_code	35-37	int	A 3-character code describing the type of record, as defined by the National Ocean Service.

The following describes the attributes for a Binary HYD93 Data Record:

Attribute	Byte Offset	Description
hyd93_survey_identifier	n/a	Survey identifier is absent in binary HYD93 records
hyd93_depth_value	9-12	Depth X 10 (in tenths of meters) (or Line Feature sequence number)
hyd93_value_type_code / hyd93_cartographic_code	13-14	type-code * 1000 + carto-code* Combines the type code field with the carto code field