Do photo sharing websites Do photo sharing websites represent a sufficient database represent a sufficient database to aid in national map updating to aid in national map updating

or change detection?or change detection?

Vyron Antoniou, Jeremy Morley, Muki HaklayVyron Antoniou, Jeremy Morley, Muki HaklayDepartment of Civil, Environmental and Geomatic Engineering

Geotagged photos in Web 2.0

Spatially explicit

Spatially implicit

Examining geotagged photos for UK

• 1 km2 National Grid for UK

• 238,920 tiles

• Distribution of 4.4 million geotagged photos

Tile statistics:

Frequencies (tile photo population)

Spatial Distribution

FlickrPicasa WebGeograph Panoramio

Expectation Surfaces

FlickrPicasa WebGeograph Panoramio

Popular tiles (>15 photos)

FlickrGeograph

≈≈5.1 %

of the total area

3.7 %

of the total area

Data Flow in popular tiles

For both sources about 3.800 of the popular tiles had geotagged photos submitted for three consecutive semesters. This is

approximately 1.6% of the total area

six months later…..

-975

15,094

DifferencesPositive: 9.2%

Negative: 1.8%

New Tiles

8554 tiles = 3.6%

1% more than 3

…but the pattern remained the sameFlickr January 2009

…but the pattern remained the sameFlickr July 2009

©Crown Copyright/database right 2009. An Ordnance Survey/EDINA supplied service.

©Crown Copyright/database right 2009. An Ordnance Survey/EDINA supplied service.

©Crown Copyright/database right 2009. An Ordnance Survey/EDINA supplied service.

??

==oror

≠≠or or

≈≈Explicit

What is the spatial distribution of changes?

oror

Changes

Implicit

Popular

User Behaviour.

Time between capturing and uploading a photograph

Conclusions

- Two types of sources: explicit and implicit

- Implicit : Huge volumes of data, poor spatial coverage

Explicit: Moderate data volume, sufficient spatial coverage

- We need the amount of data of a spatially implicit source and the spatial coverage of a explicit source

- Spatially speaking … no Long-Tail in implicit Web 2.0 apps

- We need to understand the pattern of changes on the ground

Thank you!Thank you!