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Understanding GIS Data Accuracies

You cannot use a geographic information system (GIS) for very long without encountering statements about the accuracy of a map or GIS data layer. What does it mean to say that a map or data set being used in a GIS has a horizontal accuracy of plus/minus three feet? Similarly, an important specification when acquiring or developing map information for your GIS is a statement of its accuracy. How do you determine if the map information you develop or acquire actually has the accuracy you requested? We offer two similar presentations covering these and related topics.

Portsmouth, NH, November 13

Thursday, November 13, 2008; 3:00 - 4:00
Portsmouth Department of Public Works, 680 Peverly Hill Road, Portsmouth, NH (map)

Topics in Mr. Giles' presentation will include types of accuracy standards (NSSDA, NMAS, ASPRS, State Survey Standards...), accuracy test guidelines, accuracy guidelines, applicability of accuracy testing, and accuracy testing by independent, higher accuracy methods.

After the presentation, join the informal Seacoast GIS group for their monthly gathering at the Redhook Brewery.

Auburn, MA, November 20

Thursday, November 20, 2008; 10:30 - 11:30
Auburn Town Hall, 104 Central Street, Auburn, MA (map)

Topics in Mr. Hardy's presentation will include types of accuracy standards (NSSDA, NMAS, ASPRS, state survey survey regulations such as 250 CMR in Massachusetts), understanding the methods used to develop the data sets that dictate their accuracy, accuracy test by independent, higher accuracy methods, accuracy guidelines, and applicability of accuracy testing.

NEURISA serves Connecticut, New Hampshire, Maine, Massachusetts, Rhode Island and Vermont. NEURISA is a non-profit [501(c)(6)] professional organization incorporated in Massachusetts.

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