Lecture 5 GIS Data Quality Flashcards
GIS data quality is based on two things
Attribute quality (non-spatial Data) Positional quality (Spatial Data)
What is Metadata?
Metadata is information about the data that contains information about the data source.
Main contents of metadata? 8
Who? - Author, a person, an organization
What? - main content, what is about your data
where? - Spatial coverage
why? - what is the purpose of creating the data
how? - method used to create the data
scale? - any scale info, map projection info
Any algorithms or transformations?
What are the elements of metadata? 10
Spatial data structure projection coordinate-system datum conversion or transformation scale when how field name and properties data quality/ errors accuracy and precision
Define accuracy and precision for GIS
Accuracy: the extent to which attributes and position data correspond to their real-world counterparts.
Precision: the EXACTNESS of the measurements or the number of decimal places that a device is capable of measuring.
what are the possible errors in geospatial data 5
Attribute errors positional errors Topological /geometric errors ecological fallacy Modifiable areal unit problem (MAU) T E A M P
Two common methods for determining attribute accuracy?
- Random spot checking
- Spatial sampling
what is an error matrix?
-error matrix, also known as confusion matrix or contingency table helps us determine attribute accuracy -is good for nominal or ordinal data
what is RMSE? accuracy wise?
Root Mean Square Error
the closer it is to 0, high the accuracy
further it is from 0, low the accuracy
What is the positional error? and scale_____!
Measures how close the geographic coordinates of features in a spatial data layer are to their real-world geographic coordinates
SCALE MATTERS
what to use to fix topological errors?
- use appropriate fuzzy tolerance value
- fuzzy tolerance snaps points to form a single point.
Temporal accuracy
refers to how up to date your data is
Some object of interest need to be updated every several years
some every short interval e.g. hurricanes
Ecological Fallacy
Is a belief that all observations within an area will exhibit the same or similar values for a particular characteristic
Average for a group represents individual for the same group!
What is MAUP?
- Modifiable Areal Unit Problem
- The modifiable areal unit problem is a source of statistical bias that can significantly impact the results of statistical hypothesis tests.
What is error propagation?
using datasets that originally contained errors will propagate errors in final products
