(5) Location and the Internet

• IP addresses [Internet Architecture; IP Address (1)] are globally unique (and can be geocoded [http://api.hostip.info/get_html.php?position=true])
• IP addresses are not a very reliable source for location information
  • campus wired or wireless access says I am in Berkeley, CA
  • Home access says I am in Santa Rosa, CA
  • iPhone Internet access says I am in London, UK
• Try this at home:
  1. find out your IP address [http://www.ipaddressworld.com/] (it's assigned by the Internet provider)
  2. IANA manages the basic scheme of IP address allocations [http://www.iana.org/assignments/ipv4-address-space/]
  3. ARIN is in charge of the 128.32 prefix used by UC Berkeley [http://ws.arin.net/whois/]
• Advanced Internet network configuration is more complicated
  • Network Address Translation (NAT) [http://en.wikipedia.org/wiki/Network_address_translation] hides IP addresses of devices
  • controlled networks (such as cell phone services) can be hard to figure out

(6) Determining Location

• Location can be determined in three different ways
  1. IP addresses for wired Internet access (available from IP configuration)
  2. ID of an Wi-Fi access point (available from Wi-Fi chip)
  3. ID of a tower of a mobile telephone network (available from phone chip)
  4. (and then there is GPS on some devices)
• Skyhook [http://www.skyhookwireless.com/] provides an integrated solution for determining location
• Data collection by hand and through cross-matching
  • match GPS coordinates and Wi-Fi/cell IDs
• Apple [http://www.skyhookwireless.com/inaction/] and Eye-Fi [http://www.eye.fi/] are Skyhook's biggest customers
• Wi-Fi and cell tower IDs require a lot of data
  • 100 million Wi-Fi access points
  • 1 million cell tower IDs

(7) Wi-Fi vs. Cell Location

(8) Eye-Fi Dissected

(10) Feeds are Containers

• Feeds [Content Syndication] are a format for publishing collections
• The basic feed model supports a rather limited set of features
  • title, subtitle, author, description, content
  • license, links, timestamps
• GeoRSS [http://georss.org/] extends feeds with a simple method for geocoding
  • GeoRSS-Simple [http://georss.org/simple] supports points and simple shapes
  • GeoRSS-GML [http://georss.org/gml] supports the Geographic Markup Language (GML) [http://en.wikipedia.org/wiki/Geography_Markup_Language]
  • advanced shapes (such as polygons with holes) cannot be expressed in GeoRSS-Simple

(11) GeoRSS (and other geolocation Formats)

<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#" xmlns:georss="http://www.georss.org/georss" xmlns:woe="http://where.yahooapis.com/v1/schema.rng" xmlns:flickr="urn:flickr:" xmlns:media="http://search.yahoo.com/mrss/">
 <title>Uploads from dret</title>
 <link rel="self" href="http://api.flickr.com/services/feeds/photos_public.gne?id=20266194@N00&amp;lang=en-us&amp;format=atom&amp;georss=1"/>
 <link rel="alternate" type="text/html" href="http://www.flickr.com/photos/dret/"/>
 <id>tag:flickr.com,2005:/photos/public/626282</id>
 <icon>http://farm4.static.flickr.com/3089/buddyicons/20266194@N00.jpg?1229911061#20266194@N00</icon>
 <updated>2009-04-08T00:31:46Z</updated>
 <generator uri="http://www.flickr.com/">Flickr</generator>
 <entry>

  <link rel="enclosure" type="image/jpeg" href="http://farm4.static.flickr.com/3591/3421997673_7c747786b2_o.jpg"/>
  <georss:point>37.871499 -122.257479</georss:point>
  <geo:lat>37.871499</geo:lat>
  <geo:long>-122.257479</geo:long>
  <woe:woeid>55858022</woe:woeid>

(13) Flickr and Geocoding

• Flickr supports geocoding
  • early adopters invented their own conventions for geotagging
  • Flickr quickly realized the potential and supported geocoding
  • Flickr allows to control the disclosure of location information [http://www.flickr.com/help/map/?search=location+settings#202]
• Uploaded photos may already have embedded location information
  • Exif [http://en.wikipedia.org/wiki/Exchangeable_image_file_format] embeds metadata into regular image files (JPEG [Multimedia Content; Joint Photographic Experts Group (JPEG) (1)])
  • location info can be added by Eye-Fi or by camera GPS
• Publishing JPEG can reveal a lot of information
  • it is possible to cleanse JPEG before publishing them
  • Flickr has an option to hide Exif data
  • Flickr does not strip the Exif data which can still be read

(14) Exif in Camera Images

(15) Regular Flickr Image

(16) Geocoding in Flickr

(17) Geocoding Problems

• Camera position vs. photographed object
• lens (tele vs. wide angle) make a big difference
• focus setting is interesting as well

(18) Getting GeoRSS from Flickr

• Flickr by default provides non-geotagged feeds
• adding &georss=1 to the feed URI references a GeoRSS feed
• Google Maps reads GeoRSS feeds and displays them on the map
  • simply enter the feed's URI in the Google Maps search field

(19) Flickr GeoRSS in Google Maps