1. GTECH 709 Databases
Relational databases What makes a database geographic
Geo-relational databases Locational references

2. Databases An organized collection of data A container of tables
Each table has columns (“types”)
Each table has a set of rows
Every row has the same columns

3. Relational Databases Tables have relations that link data
Relations mapping between a set of columns from table 1 to a set of columns of table 2
mapping can be implicit
or explicit (foreign key)
different types of relations:
one-to-one
one-to-many

4. Geo-relational Principle
I don’t like to repeat myself but…
To link two tables, they have to have a common identifier
Label (column header) can be different
Cell content must be a perfect match
Mismatch examples
“ ” versus
“New York” vs. “NY”
Matching addresses is particularly hard
though it does make
a user’s life easier

5. Shapefiles to Databases
CartoDB imports shapefiles
But stores the data internally in PostGIS
QGIS default storage is a shapefile
But it reads/writes many other formats
ArcCatalog (ArcGIS) default is a geodatabase
Logical organization of geographic data that practically comes in many different implementations

6. What Makes a Database Geographic
What makes data geographic?
Geographic data = space (+ time) + attributes
From this week’s lab:

7. What Makes a Database Geographic
What makes data geographic?
Geographic data = space (+ time) + attributes
From this week’s lab:
attributes

8. What Makes a Database Geographic
What makes data geographic?
Geographic data = space (+ time) + attributes
From this week’s lab:
time

9. What Makes a Database Geographic
What makes data geographic?
Geographic data = space (+ time) + attributes
From this week’s lab:
space

10. Locational References
How do we express locational references?
Absolute versus relative
Address
(Nearest) point
(Bounding) area
GIS (for analytical purposes) requires these to be always in form of coordinates
We will cover coordinate systems in two weeks
Geometric (x,y) or geographic (lat,lon)

11. Locational Reference Encoding
From our lab exercise this week:
Remember: this is how we store geography
We may then conveniently reuse coordinates to instruct GIS how to present them on a map