Qualifying All Data

No data is prefect and all data has some uncertainty.

Dimensions of data:

• Spatial: 2 or 3 dimensions
• Temporal: Typically dates but could include times
• Measurement: The value being measured

Types of errors:

• Accuracy: How close the data is to "truth". Includes:
  • Bias
  • Drift
  • Instrument Error
• Precision: How repeatable the data is
• Gross Errors: Values that are off by an amount not expected by normal

1. Estimate uncertainty
2. For each data set, research how it was collected
3. Don't assume the data is usable
4. Make sure you can read the data and display it in a GIS application