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Problem: VPFEXPORT loses certain coverage projection parameters

Description

VPFEXPORT does not maintain all projection parameters originating from the coverage, which causes some of the parameters to not translate as expected to the georeference table.

Cause

Parameters are maintained depending on which parameters are supported in the Vector Product Format (VPF) metadata and the presence of a Conversion Control File (CCF).

Note:
Projection information is contained within the geographic reference table, which is located at the VPF Library level. The contents can be viewed using VPFLIST.

Solution or Workaround

1. When converting coverages that must comply with a particular VPF product specification, convert the coverage with VPFEXPORT and allow ArcInfo to write the 'INFO' version of the georeference table.

2. When the georeference table has been created, use VPFIMPORT with the table option to import the georeference table back into ArcInfo.

3. Manually edit the metadata fields in the georeference table 'INFO', according to the VPF product specification.

4. Once the georeference table is updated, run VPFEXPORT with the table option to return it to the VPF database. The procedures remain the same if a CCF is not used during the initial VPFEXPORT and the VPF data is not meeting a particular VPF product specification.

Notes

· If the georeference table is modified to more accurately reflect the projection information, new data cannot be converted into the VPF library. ArcInfo interprets this as an attempt to convert data in one projection into a library with another.

· Another VPF file, sometimes confused with the georeference table, is the Library Attribute Table (LAT). The LAT is located at the VPF Database level. The LAT only contains the name and extent for each library in the database. There can be multiple libraries within one VPF database and each library can be in a different projection. However, the LAT only stores the minimum bounding rectangle for each library in geographic coordinates, latitude and longitude, with units of decimal degrees.

Arc: vpflist lat

VPF table name : lat
Directory path : d:\aint\vpf\mydata\hydrodb
Number of records : 3
Table description : Library Attribute Table

Column Name Type/Count/KeyType - Description - (VDT)(Index)(Narrative)
------------------------------------------------------------------------------
id I 1 U - Row id
library_name T 8 P - Library name
xmin F 1 N - Westernmost Longitude
ymin F 1 N - Southernmost Latitude
xmax F 1 N - Easternmost Longitude
ymax F 1 N - Northernmost Latitude
------------------------------------------------------------------------------

id library_name xmin ymin xmax ymax
-----------------------------------------------------------------
1 hydrolib -8.132 38.223 -7.369 38.949 <--
transverse
2 tpolylib -127.841 29.356 -108.143 50.653 <--
albers
3 ai83lib -84.605 42.708 -84.497 42.771 <--
stateplane