M1.2: Data Quality Standards

This week I completed a data quality standards assessment using the National Standard for Spatial Data Accuracy to measure and report geographic data quality as described in the Positional Accuracy Handbook. In the two provided street maps, I selected 20 points at various intersections and their matching counterparts. Afterward, I put a point where the intersection should have been for each intersection point. I then populated the attribute tables with their x and y measurements in decimal degrees. After I had all of the x and y points I filled in the horizontal accuracy statistic worksheet as shown in the worksheet and completed the formal accuracy statement.


Figure 1. The 20 intersections selected for the assessment.


Formal Accuracy Statement:

o   Horizontal Positional Accuracy:

§  Using the National Standard for Spatial Data Accuracy, the ABQ_Streets data set was compiled to meet 4.39067E-05ft and 0.001008426ft for the StreetMapUSA data set horizontal accuracy at 95% confidence level.

§  Digitized features tested 20 points for horizontal accuracy at the 95% confidence level using the NSSDA. For a complete report of the testing procedures used, contact Washington County Surveyor’s Office as noted in Section 6, Distribution Information. All other features are generated by coordinate geometry and are based on a framework of accurately located PLSS corner positions used with public information of record. Computed positions of the test points are not based on individual field surveys. Although tests of randomly selected points for comparison may show high accuracy between field and parcel map content, variations between boundary monumentation and legal descriptions of record can and do exist. Caution is necessary when using the data shown.

o   Vertical Positional Accuracy:

§  Not Applicable

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