11. Data Checks Performed by CDIAC

An important part of the data packaging process at the CDIAC is the quality assurance (QA) of the data before its distribution. Data received at CDIAC are rarely in perfect condition for immediate distribution, regardless of source. CDIAC staff members examine the data for completeness, reasonableness, and accuracy. The QA process is an important component in the value-added concept of assuring accurate, usable information for researchers. The following summarizes the QAchecks performed on the various data groups presented in this document:

  1. Data variables obtained from primary data sources were double-entered into flat ASCII computer files and proofed for discrepancies. The generated machine-readable data files were then uploaded to a Sun workstation and read into SAS. The SAS PROC COMPARE procedure was used to overlay the two versions and identify differences. All differences were then checked against the original data source, and any necessary corrections made.
  2. Data variables obtained from maps (e.g., geology) were classified and transferred to coastal segments on working maps of the coastline. The working maps were then digitized, plotted at a large scale, and compared with the original working maps and data sources. All identified discrepancies were then corrected.
  3. Maximum, minimum, and mean values were generated for all data variables and checked for reasonableness against predetermined thresholds.
  4. The data values for each data variable were mapped using the 1:2,000,000 digitized USGS line-segment coverage of the U.S. West Coast as a backdrop to check for outliers and identifiable discrepancies. The identified data items were then recalculated, and corrected if necessary.