the meaning of geographic expressions dr kristin stock [email protected]
TRANSCRIPT
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...