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Cluster-based Landmark and Event Detection
on Tagged Photo Collections
Symeon Papadopoulos, Christos Zigkolis,
Yiannis Kompatsiaris, Athena Vakali
user generated content creates new
opportunities
real-world depicted in users’ online collections
potential for many insights into what people
see, do and like




       need new tools for content organization
image clustering
clusters  landmarks + events




                                landmark

                                event
the framework
+          +


photos       tags       geo
overview




1              2

    landmark           landmark


               event
4              3
step 1: create photo similarity graph




            1                  2

                   landmark             landmark


                                event
            4                  3
SURF
     SIFT

visual similarity   casa mila, la pedrera



                      tag similarity

                         co-occurrence
                    latent semantic indexing
step 2: use graph to cluster the photos




            1                  2

                   landmark             landmark


                                event
            4                  3
the concept of node structure


 neighborhood of node v   + node itself   = structure of node v



                 v             v                    v




          N(v)                  v                  Γ(v)
the concept of structural similarity (1)




            v
                         u




            Γ(v) ∩ Γ(u)
                              structural similarity between nodes v and u

                Γ(v)  Γ(u)
the concept of structural similarity (2)


 high structural similarity
                                       photo cluster 1
                        C
                               A
                                   B



             photo cluster 2
 low structural similarity
# edges
complexity
                                     O (km  m)            graph-based clustering


                                  average node degree

                                                        # dimensions
                                         # clusters


             k-means clustering          O (I  C  n  D)

                                    # iterations
                                               # nodes


                                     O (n2  log n)
                         hierarchical agglomerative clustering
step 3: detect landmarks & events




            1                 2

                  landmark            landmark


                              event
            4                 3
#users / #photos                baseline features



                                            [2 years, 50 users / 120 photos]
         [1 day, 2 users / 10 photos]




      Quack et al., CIVR 2008                                 duration
Landmark Tags   additional
                  features




                    Event Tags
step 4: post-process landmark clusters




            1                 2

                  landmark             landmark


                               event
            4                 3
cluster merging based on proximity
cluster tag filtering




                                 CLUSTER TAGS

            helado   tropical   barcelona        cielos   spain      field

            park güell          jaume oller   park   sclupture   el beso



       low frequency tags
                                                     generic tags
results
207,750 photos
7,768 users
33,959 unique tags

compare graph-based vs. k-means clustering
     user study             geospatial coherence

                  high geospatial
                  coherence

                                              low geospatial
                                              coherence
user study
                             VISUAL
                 precision    recall   κ-statistic

   graph-based    1.000       0.110      1.000

   k-means        0.806       0.324      0.226


                              TAG
                 precision    recall   κ-statistic

   graph-based    0.950       0.182      0.820

   k-means        0.848       0.307      0.564
geospatial coherence
                                  VISUAL
                              radius     std. deviation

                graph-based   357 m          1.18 km

                k-means       2.4 km         1.73 km

                                       TAG

                graph-based   456 m          1.15 km

                k-means       767 m          1.76 km
classification performance



     16% - 23%
            improvement thanks to tag features
landmark localization accuracy


                     sagrada familia, cathedral, catholic   15.2m



                     la pedrera, casa mila                  31.8m



                     parc guell                              9.6m



                     boqueria, market, mercado, ramblas     82.1m



                     camp nou, fc barcelona, nou camp       18.7m
event category composition



                        music, concert, gigs, dj     43.1%




                        conference, presentation     6.5%




                        local traditional, parades   4.6%




                        racing, motorbikes, f1       3.3%
clusttour




                www.clusttour.gr

twitter.com/clusttour       facebook.com/clusttour

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Cluster based landmark and event detection for tagged photo collections

  • 1. Cluster-based Landmark and Event Detection on Tagged Photo Collections Symeon Papadopoulos, Christos Zigkolis, Yiannis Kompatsiaris, Athena Vakali
  • 2. user generated content creates new opportunities
  • 3. real-world depicted in users’ online collections
  • 4. potential for many insights into what people see, do and like need new tools for content organization
  • 6. clusters  landmarks + events landmark event
  • 8. + + photos tags geo
  • 9. overview 1 2 landmark landmark event 4 3
  • 10. step 1: create photo similarity graph 1 2 landmark landmark event 4 3
  • 11. SURF SIFT visual similarity casa mila, la pedrera tag similarity co-occurrence latent semantic indexing
  • 12. step 2: use graph to cluster the photos 1 2 landmark landmark event 4 3
  • 13. the concept of node structure neighborhood of node v + node itself = structure of node v v v v N(v) v Γ(v)
  • 14. the concept of structural similarity (1) v u Γ(v) ∩ Γ(u) structural similarity between nodes v and u Γ(v)  Γ(u)
  • 15. the concept of structural similarity (2) high structural similarity photo cluster 1 C A B photo cluster 2 low structural similarity
  • 16. # edges complexity O (km  m) graph-based clustering average node degree # dimensions # clusters k-means clustering O (I  C  n  D) # iterations # nodes O (n2  log n) hierarchical agglomerative clustering
  • 17. step 3: detect landmarks & events 1 2 landmark landmark event 4 3
  • 18. #users / #photos baseline features [2 years, 50 users / 120 photos] [1 day, 2 users / 10 photos] Quack et al., CIVR 2008 duration
  • 19. Landmark Tags additional features Event Tags
  • 20. step 4: post-process landmark clusters 1 2 landmark landmark event 4 3
  • 21. cluster merging based on proximity
  • 22. cluster tag filtering CLUSTER TAGS helado tropical barcelona cielos spain field park güell jaume oller park sclupture el beso low frequency tags generic tags
  • 24. 207,750 photos 7,768 users 33,959 unique tags compare graph-based vs. k-means clustering user study geospatial coherence high geospatial coherence low geospatial coherence
  • 25. user study VISUAL precision recall κ-statistic graph-based 1.000 0.110 1.000 k-means 0.806 0.324 0.226 TAG precision recall κ-statistic graph-based 0.950 0.182 0.820 k-means 0.848 0.307 0.564
  • 26. geospatial coherence VISUAL radius std. deviation graph-based 357 m 1.18 km k-means 2.4 km 1.73 km TAG graph-based 456 m 1.15 km k-means 767 m 1.76 km
  • 27. classification performance 16% - 23% improvement thanks to tag features
  • 28. landmark localization accuracy sagrada familia, cathedral, catholic 15.2m la pedrera, casa mila 31.8m parc guell 9.6m boqueria, market, mercado, ramblas 82.1m camp nou, fc barcelona, nou camp 18.7m
  • 29. event category composition music, concert, gigs, dj 43.1% conference, presentation 6.5% local traditional, parades 4.6% racing, motorbikes, f1 3.3%
  • 30. clusttour www.clusttour.gr twitter.com/clusttour facebook.com/clusttour