The following steps were taken in the conversion of the data from the DCW
format to ARC/INFO format:
- Extraction of data: Using a program called WIRE, VECTOR and POINT (developed by Peter Schickel, firstname.lastname@example.org), the selected
layers were extracted from DCW on CD-ROM to create several files in ASCII format.
- Processing ASCII files: Before they could be converted into an ARC/INFO
coverage, these ASCII files, some of which did not meet ARC/INFO's requirements, needed to be processed further. The rearrangements necessary were carried out using UNIX commands and a C program.
- Generating ARC/INFO coverage: The post-processed ASCII files were used to create a corresponding ARC/INFO coverage, using the GENERATE command. A table of corresponding attributes was also created and joined with the coverage.
- Joining tiles: The DCW data are stored in tiles. Each tile covers an area of 5 degrees by 5 degrees. DCW_CHN involves about 66 tiles, while DCW_PLUS covers 140 tiles. These tiles were joined together to form a coverage of the whole country.
- Clipping of features that are out of the country boundary: Tiles on the boundary include area that lies outside of China. Those parts have been erased, using a country boundary coverage. This was done only to those la
yers in DCW_CHN sub_set.
(1) These coverages are in geographic coordinate system -- no projection was performed.
(2) Because of the extracting software used (WIRE, VECTOR, and POINT), some secondary attributes were left out during the conversion process. This includes STATUS in the road and railroad coverages, and TYPE in the contour coverage. This
should not be a problem for most users. If someone needs such secondary attributes, he/she will need to look into other sources.