World Explorer (JCDL 2007 Best Paper)

World Explorer: Visualizing Aggregate Data from Unstructured Text in Geo-Referenced Collections Shane Ahern, Mor Naaman, Rahul Nair* & Jeannie Yang Yahoo! Research Berkeley

Attraction Map of Paris
Stanley Milgram, 1976.
Psychological Maps of Paris

Attraction Map of Paris
Y!RB, 2007.

Flickr “geotagged”
20+ million images
Can we do better?

Location-driven Modeling
Derive meaningful data about map regions
E.g., representative tags, photos

Data Description

Issues
Sparse data set
Photographer bias
In location
In tags
Incorrect data

Heuristics
Number of photographs denotes the “importance” of a location
Users will use a common subset of tags to describe objects/locations
Concentrated tag usage indicates descriptiveness

Algorithm
Clustering: k-Means, get set of k clusters
“ Document” C is bag of all tags in cluster
For each tag in C calculate:
TF = |P(C,t)|
IDF = |P(R)| / |P(R, t)|
UF = |U(C,t)|/|U(C)|

Scoring
Score (t) = TF * IDF * UF
Threshold values
30+ photographs
Minimum 3 users
Score > 1
Final dataset: (tag, score, latitude, longitude)

Precomputation
Divide the world into equal sized non-overlapping tiles
Compute and store the tags for each tile
Repeat for different zoom
levels

Retrieval
Find the tile level closest in size to the request area
Select the tiles that fully cover the request area
Return the tags that fall within the request area

User Study
10 subjects
6 female, 4 male
Ages 20-60
Varying technical knowledge
No geotagged photos of their own

Experiment tasks
Vacation recap
San Francisco tour
Explore a new city

Recall
Reminded the subject about locations
“It brings out memories”
“Oh my God! This place has the best restaurants”
“We wanted to see the Polynesian Cultural Center"

Discovery
Participants discovered previously unknown locations and events
“I’ve never heard of this festival”
“There is car racing which I'd probably go see”

Needle & Haystack
Excellent visualization of the Haystack
Hard to find specific information
“Where was Culver City again?”
No way to search
“I guess what I’m looking for are bull fighting pictures”

Other Responses
Gets the “vibe” of a place
Share with other people
Tags did not always match the mental model of a location
Wanted more tags
Want more info about tags

Conclusions
Extracted meaningful aggregate information from georeferenced data
Allows users to explore locations in a new way
Users like using the overview but also want the ability to search

Future work
Adding search capability
Show photos in places with no tags
Differentiate locations and events
Apply to other types of georeferenced data

tagmaps.research.yahoo.com
World Explorer
Data API
Visualization toolkit
Trip Explorer
Night Explorer

Questions? Rahul Nair [email_address] http://tagmaps.research.yahoo.com

World Explorer (JCDL 2007 Best Paper)

by rnair on Jun 21, 2007

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World Explorer (JCDL 2007 Best Paper) — Presentation Transcript