Editing and QAQC Process Overview

The Sewer Atlas database is updated on an ongoing basis, with (approximately) quarterly updates made available for download and published as web map services.

The editing process entails four general steps:

  • pre-processing: source data, which is of various qualities, consistencies, and formats, is extracted, transformed, and loaded into a set of tables designed to transfer record and attributes-level changes to the database directly.
  • editing: the Sewer Atlas database is updated to match the source data
  • QA/QC: check that edits are comprehensive, conflicts are resolved, and network connectivity has been maintained
  • post-processing: a snapshot of the database is exported and transformed into formats for download and publication as web services

This page highlights the some of the steps in that process.

Editing

When editing the Sewer Atlas data, we follow several general rules:

  • Editing entails moving the Sewer Atlas geometry to match the source data geometry
  • Unless: matching the source data exactly would break the geometric network topology, in which case we balance geometric precision with network-correctness
  • Never delete segments/nodes, only disable them
  • Unless: the segments/nodes are verified as erroneous by the data source maintainer
  • When working through conflicts, defer to data authorities in this order:
  • ALCOSAN datasets (e.g., RI) > Municipal Source Dataset > Existing Sewer Atlas

QAQC

Our QAQC process emphasizes a few things:

Overall completeness of edits

As a first pass at QAQC, we compare the source tables to the editing database on geometry simply to identify any areas we might have missed.

Connectivity

All updates prioritize maintainging the topological intergrity of the network model for reliable inter- and intra-municipal tracing. Even when the submitted data is not topologically clean (and it often isn’t), the Sewer Atlas maintains the topology and connectivity that is implied in the data submission.

After the incorporation of municipal data, topology checks on the Sewer Atlas are largely handled by implementing Esri’s Geometric Network data type, through which the topological rules required for maintaining the needed connectivity are implemented, and errors are identified on network build.

As a final check, upstream tracing from the ALCOSAN plant is performed iteratively to identify and correct any remaining disconnected areas of the network that the geometric network topology rules do not account for.

Missing/empty attributes

Occasionally, our conflation process does not work; we use a map with labels and symbology designed to call out edited features with attributes that didn’t transfer from the source.

Conflict Resolution

If needed, we bring up with the data source maintainer ay conflicts between the source and editing database that have no obvious solution. Typically, the course of action is fairly clear, but occassionally it isn’t. We flag those without a clear resolution as Issues, which appear in a layer shown on the Sewer Atlas Data Status Dashboard.