How To: Change the library tile structure


Changing project needs, a more mature understanding of LIBRARIAN, or other factors may generate the need to redesign the library tiling structure. Instructions provided describe how to change the library tile structure.

The main constraint is that a tile is restricted to one polygon, allowing for no internal islands or donut polygons. Avoid concave or sinuous tiles. A tile or tile group can be disjoint for other tiles or tile groups. Each tile must have exactly one label point.

Before re-tiling, a needs-assessment and a design plan should be performed to make sure the new tiling structure meets the needs of the library users. Consider these factors: how data is collected, how users access and extract library data, and how library data is to be updated.

Before re-tiling the layer, back up the library tile directories and database directory. Review the library architecture as shown in the "Using Map Libraries User's Guide." In particular, make sure it is understood that the TILE_NAME and LOCATION items in the .../DATABASE/INDEX coverage PAT are pointers to the library's tile directories.

Here is a sample procedure for re-tiling a library: In this case, the new tiling scheme involves splitting one tile in half.

- ARC COPY the INDEX coverage to a new workspace, calling the new coverage NEWINDEX.

- Use ARCEDIT to add an arc to NEWINDEX. The new arc splits one tile polygon in half, creating two new half-tile tile polygons.

- BUILD NEWINDEX with the POLY option.

- INFO UPDATE the NEWINDEX.PAT file with the correct values for TILE-NAME and LOCATION. You provide new tile names and locations for both new half-tile tile polygons.

- Use ARC CREATEWORKSPACE to create the two new tile directories in the location indicated by the LOCATION item on NEWINDEX.PAT.

- Use the ARC RESELECT and SPLIT commands to create new map section pairs from each map section in the old tile directory. Create a two-polygon split coverage from the NEWINDEX coverage by doing an ARC RESELECT on the TILE-NAME item in the NEWINDEX.PAT. For each layer, ARC SPLIT the layer map section in the abandoned tile into two map sections. Use the split coverage just created and respond to the SPLIT prompts "Enter the 1st coverage" and "Enter the 2nd coverage" with pathnames to the new half-tile tiles. SPLIT creates the half-tile map sections in the new tile directories.

- ARC RENAME the old .../DATABASE/INDEX directory to ORIGINDEX. ARC COPY the NEWINDEX coverage into the .../DATABASE directory, calling the copied coverage INDEX. Run the ARC INDEX command with the POLY option on the newly named INDEX coverage.

- Run the LIBRARIAN command VERIFYLAYER with the UPDATE option on every layer in the library. VERIFYLAYER populates the layer item on the INDEX.PAT with a "P" if the new half-tile tile directories contain data for the layer. Otherwise, an "N" is written to the layer item.


Sometimes a library is planned to have many tiles, but there is only data for a few tiles. In this case, consider making an original .../database/index coverage that contains all of the tiles that eventually contain data. Speed up LIBRARIAN and ARCPLOT layer processing by leaving the INDEX.PAT LOCATION item blank for those tiles lacking any layer data. In ARCPLOT, the map extent can be set to the currently active tiles using the MAPEXTENT TILES option.