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Data Quality Two types of geographic areas are of special interest. For Urban Areas, the data should have the currency and positional accuracy qualities typically sought by local governments. For large areas (for example, States or groups of States), the data should have the positional accuracy qualities of USGS primary topographic map series (typically 1:24,OOO-scale; 1:63,360-scale in Alaska). Table 22 provides minimum goals for these two classes of data. Table 22 - Minimum ("no worse than") Goals for Resolution, Accuracy, and Currency Urban Areas Large Areas Data Theme Minimum Resolution or Minimum Minimum Resolution or Accuracy 11 Minimum Accuracy 11 Currency 18 Currency Orthoimagery 1 foot resolution; 3 meters Two years 1 meter resolution; 11.70 meters horizontal Five years horizontal accuracy accuracy Elevation 1/9 arcsecond (-3 meters) Two years 1/3 arcsecond (-10 meters) (2 arcsecond in Five years resolution; 0.73 meter vertical Alaska) resolution; vertical accuracy accuracy commensurate with contour interval of USGS primary topographic map for area Hydrography 4.68 meters horizontal accuracy Two years 13.90 meters horizontal accuracy; 36.69 meters Five years horizontal accuracy for Alaska Transportation 4.68 meters horizontal accuracy Two years 13.90 meters horizontal accuracy; 36.69 meters Five years horizontal accuracy for Alaska Boundaries 4.68 meters horizontal accuracy Two years 13.90 meters horizontal accuracy; 36.69 meters Five years horizontal accuracy for Alaska Structures 4.68 meters horizontal accuracy Two years 13.90 meters horizontal accuracy; 36.69 meters Five years horizontal accuracy for Alaska Land Cover Should align with base maps that Two years Should align with base maps that have the Five years have the accuracies listed above. accuracies listed above. Geographic Same as the associated feature Same as the associated feature Names C. Relevant Organizations and Initiatives The following describes important organizations and those Federally-maintained, endorsed or adopted initiatives that grantees are strongly recommended to review: 17,4 Accuracy statement based on Geospatial Positioning Accuracy Standard, Part 3, National Standard for Spatial Data Accuracy (FGDC-STD-007.3-1998). http://www.fgdc.gov/standards/status/subl_3.html. For horizontal accuracies (95% confidence level), 3 meters is commensurate with 1 :3,075-scale maps under the National Map Accuracy Standard, 4.68 meters with 1 :4,800-scale maps, 13.90 meters with 1 :24,000-scale maps, and 36.69 meters with 1 :63,360-scale maps. For vertical accuracy (95% confidence level), 0.73 meter is commensurate with a four- foot contour interval under the National Map Accuracy Standard. 18,5 Estimated currency of the data at the date of service initiation; that is, the data served reflects the ground condition sometime during the two (or five) years prior to the start of service through The National Map. (Note that, for themes in which the ground changes rarely, older data might meet this condition.) 19 Data should be in the North American Datum of 1983; elevation data in the North American Vertical Datum of 1988. H-3