Data Quality for GIS
	GIS quality-related issues
	Data Quality
	GIS Projects – Cost versus Accuracy: Hypothetical Example
	Request to develop land use layer for Texas town
	Data Quality Concepts
	Accuracy, precision, resolution
	Types of accuracy requirements
	Types of error
	Positional error
	Source of the “true value” for estimating accuracy?
	US National Map Accuracy Standards (Paper Maps)
	“Source scale” is one determinant of positional accuracy
	About Scale
	Large and Small Scale Maps
	Scale 1:100,000 (1 inch approx 1.58 miles)
	Scale 1:24,000
	Scale 1:10,000
	Scale 1:2,000
	Relation between positional error and scale
	NMAS Standards
	Digitizing paper maps adds error
	Attribute accuracy
	Logical Consistency
	Completeness Is the data set “complete”?
	Currency: Is the data set current? No!
	Ensuring data quality
	Ensuring data quality
	Ensuring data quality
	Documenting data quality
	What positional accuracy do you need?
	What attribute accuracy do you need?
	GIS quality-related issues
	Metadata is critical!
	Web sites with more information
	Learn more about metadata
	Metadata examples

• Using Tools for Querying
• Creating a Map with ArcMap
• Assessment of Groundwater Vulnerability to Landfill Leachate Induced Arsenic Contamination in Maine, U.S.: Paper
• Geocoding Overview and Preparation
• Georeferencing a Scanned Map