MAPJOIN (CLEAN or BUILD) returns: mismatch border segments (NODPOL)

Last Published: April 25, 2020

Solution or Workaround

When mapjoining coverages of adjacent geographic areas, MAPJOIN bails out and returns the following error message:

"Appending coverages...
Partial process enabled. 61% of the coverage will be processed.
Assembling polygons...
Mismatch of border segments (NODPOL)
Bailing out of BUILD"

This message may also be encountered when running CLEAN or BUILD.


The error message may occur for one of the following reasons:

1. Occasionally, an MSK file is present in one or both of the original coverages. The MSK file is a bitmap file containing the map extent of a previous editing session in ARCEDIT. It is used by BUILD and CLEAN to process only those portions of the coverage that were last updated. The MSK file is deleted after the coverage topology has been updated. Deleting the MSK file(s) and/or rebuilding topology for the original coverage(s) usually resolves the situation.

A new MSK file is created during the MAPJOIN process to enable partial processing of the border areas of the maps. The new MSK file is not related to pre-existing MSK files in the input coverages.

2. If no MSK file is present, then this may be the result of misaligned coverages. MAPJOIN searches for matching nodes within the specified fuzzy tolerance, and if there are ambiguous cases, the (NODPOL) error occurs. The solution is to verify that the coverages have been edgematched. If not, then the more 'spatially accurate' coverage must be selected as the LINK coverage and edgematch the less accurate coverage to it. See the ADJUST command in the ARCEDIT Command Reference and "Rubber sheeting and edgematching" in "Editing Coverages & Tables with ARCEDIT".


If the coverages have already been edgematched, specify a larger fuzzy tolerance for both coverages using the TOLERANCE command. Alternately, CLEAN each coverage separately with the appropriate fuzzy tolerance values and then use MAPJOIN. Finding the appropriate fuzzy tolerance value requires an understanding of the minimum coordinate resolution for the coverages (see "The ARC/INFO Data Model: Coverage processing tolerances" in the ARCEDIT Command Reference for more information about fuzzy tolerance). As a rule of thumb, increase the fuzzy tolerance by increments of 1 1/2 times or decrease it by 1/4 times, and the error message should no longer occur.
Sometimes this can be resolved by joining the coverages in parts. For example, if there are 12 coverages to join, first try joining 6 coverages together. If the MAPJOIN still fails, try joining only 2 coverages together. This approach allows one or two coverages to be singled out, which may be causing the entire process to fail. Once the coverages have been fixed, they should be able to be joined to the rest of the coverages.

See the ARC Command Reference for more information on MAPJOIN.

Article ID:000001258

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