This document discusses various aspects of working with geo-data in PHP, including background on geographic coordinate systems, common data formats, techniques for extracting geo-data from IP addresses, image metadata, and text, storing geo-data in databases and file formats, performing spatial analysis and calculations, and visualizing geo-data on maps. It provides code examples for geocoding IP addresses, reading EXIF data, distance calculations, and more.

1. Where in the World?Geo-data in PHP

2. 80% of data has a geo-component

3. Some background

4. Mercator - 1569

5. 51 28’ 38”N0 0’ 0” EMunich, 11EParis, 2EMadrid, 3WPrime meridianKnow your datum!

6. PointsParis52°20'28N, 04°53'25E12 Grimmauld Place, LondonWhat makes up geo-data?

7. LinesM4Sunset BoulevardDover TSSWhat makes up geo-data?

8. PolygonsLondonSomersetContourWhat makes up geo-data?

9. Is point x within y?Questions, questions…

10. Does line x pass through y?Questions, questions…

11. How far is point x from point y?Questions, questions…

12. Which region is point x within?Regions can overlap:District: ClaphamBorough: WandswothCity: LondonCountry: UKQuestions, questions…

13. 80% of data has a geo-componentSo how do I find it?

14. Geo-data from web visitors

15. Every web visitor offers 2 sources of geo-data: IP address

16. Ask the browser!Where is my visitor?

17. home51 26’ 55.2” N0 0’ 0.1” WexchangeAccurate?IP gives you the location of the Serving area interface (telco exchange).Some exchanges can be 5 miles away!homeofficeReliable?ProxiesVPNsNetwork distributions (ever tried geo-locating an AOL IP?)exchangeThe problem with IP

18. include("geoip.inc"); $gi = geoip_open("/usr/local/share/GeoIP/GeoIP.dat",GEOIP_STANDARD);$country_code = geoip_country_code_by_addr($gi, "24.24.24.24");$country_name = geoip_country_name_by_addr($gi, "24.24.24.24”); Free data library from MaxMind….Pure PHP

19. Pear extension

20. Apache moduleUse the code…

21. function myCallback(position) { // called if the browser reports its location}if (navigator.geolocation) {navigator.geolocation.getCurrentPosition(myCallback);}W3C spec:http://dev.w3.org/geo/api/spec-source.htmlMozilla, where art thou?

22. Geo-data from content

23. “Journey’s End”by nathanhayag“MacRitchie Reservoir, Singapore”Geo-data encoded in the image file:1°22'18”N103°49'27"EA picture says a thousand words

24. $exif = exif_read_data('file.jpg');$long[‘deg’] = $exif['GPSLongitude'][0];$long[‘min’] = $exif['GPSLongitude'][1] / 60;$long[‘sec’] = $exif['GPSLongitude'][2] / 3600;$lat[‘deg’] = $exif['GPSLatitude'][0];$lat[‘min’] = $exif['GPSLatitude'][1] / 60;$lat[‘sec’] = $exif['GPSLatitude'][2] / 3600;Reading EXIF

25. “Journey’s End”by nathanhayag“MacRitchie Reservoir, Singapore”Parse text for location data….Usual PHP information retrieval techniques applyhttp://phpir.com/ to learn moreA picture says a thousand words

26. “Journey’s End”by nathanhayag“MacRitchie Reservoir, Singapore”Feeling brave?Image recognition and associationA picture says a thousand words

27. External sources

28. Don’t forget…

29. Primitive data-types$long = 51.5723$lat = -0.0179Class structures$point = new GISPoint;$point->setLatitude(51,21,35,'N');$point->setLongitude(0,1,21, 'W');Geo-data in PHP variables

30. MySQL storageCREATE TABLE tweet( id BIGINT, user VARCHAR(15), message VARCHAR(140), location VARCHAR(16) );INSERT INTO tweet VALUES ( 15924144610, 'manarth', 'hello!', '0512732N0000319W' ); Persistent storage

31. MySQL Spatial extensionsCREATE TABLE tweet( id BIGINT, user VARCHAR(15), message VARCHAR(140),location POINT );INSERT INTO tweet VALUES ( 15924144610, 'manarth', 'hello!',PointFromWKT(Point(51.1,-0.2)) ); Spatial extensions

32. MySQLMS SQLOraclePostgres – PostGISGeo-data in the DB

33. WKT: Well Known TextPOINT(6 10) LINESTRING(3 4,10 50,20 25)WKB: Well Known Binary1010010001001010GeoJSON{ "geometry": { "type" : "Point", "coordinates" : [97.03125, 39.7265625] }}Write to disk?

34. Binary TerrainCoverage (ArcGIS)DEM Spatial Data File (Autodesk)…More (obscure) formats

35. DiscoveryStorageAnalysis

36. Geo-centric:Cartesianhttp://trac.osgeo.org/proj/wiki/man_cs2csCoordinate conversion

37. Cartesian geometrya(x1, y1)√(y1 – y2)2 + (x2 – x1)2y1 – y2bx2 – x1(x2, y2)Distance from a to b

38. Geo-centric geometryGreater circle routea(λs, Φs)Haversine formulab(λf, Φf)Distance from a to b

39. function haversine($a) { return (sin($a/2) * sin($a/2));}function ahaversine($a) { return 2 * asin(sqrt($a));}function haversine_separation($a, $b) { // assume a radius of 3956 miles. define ('RADIUS', 3956); // convert degree inputs to radians $a = array(deg2rad($a['long']), deg2rad($a['lat'])); $b = array(deg2rad($b['long']), deg2rad($b['lat'])); $x = haversine($a['long'] - $b['long']) + (cos($a['long']) * cos($b['long']) * haversine(abs($a['lat'] - $b['lat']))); // $d (distance) is therefore R * inverse haversine($x) $d = RADIUS * ihaversine($x); return $d;}Haversine calculations

40. SELECT DISTANCE(a, b);SELECT INTERSECTS (a, b);SELECT DISJOINT (a, b);SELECT OVERLAPS (a, b);SELECT CONTAINS (a, b);SELECT WITHIN (a, b);Some limitations – currently measures against MBR – Minimum Bounding RectangleSpatial analysis in MySQL

41. DiscoveryStorageAnalysisVisualisation

42. Map APIs

43. Simple overlays

44. Heatmaps

45. Custom visualisation

46. Image generation

47. Upcoming conferencesBristol Indiemedia Bristol – June