Format Specifics - GDF-AS
GDF-AS files can be viewed directly as ASCII files with a simple text editor. All GDF-AS files have a .gdf file extension.
General GDF-AS Record Conventions
- 1st and 2nd positions indicate record type;
- Length of each line = 80;
- If 80th position is = 0, record ends;
- If 80th position is = 1, record continues on next line;
- If 1st and 2nd positions are = 00, record from previous line continues;
- If 1st and 2nd positions are =90, it is a comment line.
Record Organization in GDF-AS Files
Notes on the Order of Records
The Dataset Header Record indicates the beginning of a dataset. The dataset ends with the next Dataset Header Record or with a Volume Termination Record with a Volume Termination Mark = 0 (last volume in an album).
The Section Header Record immediately follows the Dataset records. Its first appearance indicates the beginning of the first section. The section logically ends at the occurrence of another Section Header Record with a different Section ID or with a Volume Termination Record having a Volume Termination Mark = 0 (last volume of an album). If a section logically continues on the next volume, the corresponding Section Header Record has to be repeated.
The Layer Header Record immediately follows the Section Header Record. This record indicates the beginning of a new layer. A layer ends at the occurrence of another Layer Header Record. The last layer of a section ends with either a Conversion Record, a Semantic Relationship Record, a Section Header Record, a Volume Termination Record or a Data Set Header Record.
The Data Records immediately follow the Layer Header Record. The data records belonging to the last layer in a section are followed by zero or more Relationship Records possibly accompanied with one or more Comment Records. These Records do not belong to one particular layer, because they may contain information that refers to features that belong to different layers.
Comment Records are allowed to be written anywhere in the file between the Volume Header Record and the Volume Termination Record. A Comment Record cannot be inserted between two physical records belonging to one logical record.
GDF-AS and GDF-AR Dataset IDs
Countries Outside of United States and Canada MultiNet
| COUNTRIES OUTSIDE OF U.S. AND CANADA | MULTINET 3.6.x |
|---|---|
| Dataset Identifier | 1276 |
| Section Identifier | 58001024 |
The internal dataset identifier will always begin with 01 (Leading zeros will not be shown for single digit internal dataset identifiers. This is valid for dataset IDs of all countries.)
United States and Canada MultiNet
| UNITED STATES AND CANADA | MULTINET 3.6.x |
|---|---|
| Dataset Identifier | 25840 |
| Section Identifier | 30000236 |
A two-digit FIPS State or Province code appears before the three-digit ISO country code.