The Meaning of Geographic Expressions

Dr Kristin Stockkristin.stock@nottingham.ac.uk

65%

4%

22%

9%

Q. These houses look like:

1. Comfortable homes2. A retirement village3. A slum4. Mansions

21%

13%

29%

38%

Q. I would describe this geographic feature as:

1. A hill2. An island3. A volcano4. A cay

Little round planetIn a big universeSometimes it looks blessedSometimes it looks cursedDepends on what you look at obviouslyBut even more it depends on the way that you see

Bruce Cockburn

What does it all mean?

How Do People Think? How Do Computers Think?

Bridging the gap...

What is a geographic expression?

• National Parks near Nottingham.• Walking paths in the Peak District.• The river is opposite the museum.• The library is around the corner from the market

square.• The castle is near here.• Which rivers go through the Lake District?• Which mountains in the Alps are steep?• Where is a large lake near Nottingham?

Geographic Expressions aremade up of...

• Geographic Features

• Spatial Relations

• Geographic Qualifiers

Geographic Features• Objects that have a location relative to the earth.• Natural, person-made or administrative.• Categories or instances (instance = a specific object).• Usually nouns in English.

Spatial Relations• Words that describe the relationship in space between

two features.• Usually verbs in English.

Geographic Qualifiers• Further restrict or qualify a geographic

feature.• Sometimes vague in interpretation.• Usually adjectives in English.

83%

4%8%4%

Q. The parts of these expressions shown in red are:

• National Parks near Nottingham.

• Walking paths in the Peak District.

• The river is opposite the museum.

• The library is around the corner from the market square.

• Is the castle near here?• Which rivers go through the

Lake District?• Which mountains in the Alps

are steep?• Where is a large lake near

Nottingham?

1. Geographic object categories2. Geographic object instances3. Spatial relations4. Geographic qualifiers

63%

33%

0%0%0%4%

Q. An example of a spatial relation is:

1. around the corner2. go through3. tallest4. Nottingham5. River6. step-mother

8%4% 4%

0%

84%

Q. ‘large’ is:

1. A geographic object category2. A spatial relation3. A geographic qualifier4. A geographic object instance5. An administrative relation

Spatial Relations Exercise

12%

0%4%

54%

31%

Q. I would describe this geographic feature as a:

1. Creek2. Beck3. River4. Stream5. Road

42%

8%

12%

0%

27%

12%

Q. I would describe this geographic feature as a:1. Hill2. Hillock3. Mountain4. Tor5. Munro6. Pingo

How do the meanings of geographic expressions vary?

• Culture.• Background.• Education.• Environment.• Context (dynamic).

So, how do people think about geographic features?

• Differently from each other (to varying degrees).

• Sometimes vaguely.• Sometimes context sensitively.

But, how do computers think about geographic information?

Geographic Expressions

• Have a precise, fixed meaning:– The same for everyone;– Not context sensitive;– Not vague.

• Have rigid, crisp (not fuzzy) physical boundaries.

Geographic Features

• Census output area polygons, lower level super-output area polygons, ward polygons.

• County polygons.• National Park polygons.• Road network.• Buildings from Historical Digimap.

Spatial Relations

• Query operators allowed by ArcMap:– Intersect– Completely contain– Share a line segment with– Touch the boundary of– Have their centroid in

• Like geographic features, spatial operators in GIS are also crisp and rigid.

20%

0%

8%

36%36%

0%

Q. Which spatial operator would you use to: ‘find the buildings in Smith Street?’

1. Contains2. Crosses3. Overlaps4. Touches5. Within6. Near

48%

20%

4%

28%

Q. How would you query geographic qualifiers(steep, large) in a GIS?

Geographic Qualifiers

1. I would look for an attribute containing the relevant information.

2. I would look at the spatial relations to try to deduce the qualifier values.

3. I would ask the person next to me.

4. I wouldn’t.

Summary• People think uniquely, context-sensitively,

sometimes vaguely.• Computers think precisely, crisply, uniformly.• When using current mainstream GIS, people

have to bridge the gap.• We are working on ways to help computers

bridge the gap...