Presentation given at Syracuse PHP User's Group on geolocation and how to work with coordinates to find out where things are and what’s nearby.

1. GEOLOCATION
Timothy Boronczyk
Syracuse PHP Users Group
September 29, 2016

2. Timothy Boronczyk
Senior Developer at Optanix, Inc.
Former Managing Editor of phpmaster.com
Author
 CentOS 7 Server Deployment Cookbook
 Jump Start MySQL
 Beginning PHP6, Apache, MySQL Web Development
 PHP and MySQL: Create, Modify, Reuse
zaemis.blogspot.com @zaemis

3. Geolocation describes the
real-world position of objects
using coordinates.

4. Geodetic Systems
Latitude and Longitude

5. Geodetic Systems
CH1903
ED 50
ETRS89
GCJ-02
GDA94
JGD2011
NAD83
OSGB36
RT90
SAD69
WGS84

6. IP-based geolocation uses the
user’s IP address to determine
their general location.

7. Database Web Service
 IP2Location
 MaxMind GeoIP2
 MaxMind GeoLite2
 MaxMind GeoIP2
Precision Services
 Neustar IP Intelligence
 ipinfo.io
 geoPlugin.com

9. use GeoIp2DatabaseReader;
$reader = new Reader('Geolite2-City.mmdb');
$record = $reader->city($_SERVER['REMOTE_ADDR']);
$city = $record->city->name;
$state = $record->mostSpecificSubdivision->name;
$img = imagecreatefromjpeg('singles.jpg');
for ($i = 0; $i < $numProfiles; ++$i) {
$x = $startX + ($profileWidth * $i);
imagettftext($img, $fontSize, 0, $x, $cityY, $color, $font, $city);
$x = $startX + ($profileWidth * $i);
imagettftext($img, $fontSize, 0, $x, $stateY, $color, $font, $state);
}
header('Content-Type: image/jpeg');
imagejpeg($img);

10. GeoLite2 City Database
city->geonameid
city->name
continent->code
continent->geonameid
continent->name
country->geonameid
country->isoCode
country->name
location->accuracyRadius
location->latitude
location->longitude
location->metroCode
location->timeZone
postal->code
subdivisions[]->geonameId
subdivisions[]->isoCode
subdivisions[]->name
mostSpecificSubdivision->*

11. geoPlugin.com Web Service
www.geoplugin.net/json.gp?ip=<ADDRESS>
geoplugin_latitude
geoplugin_longitude
geoplugin_regionCode
geoplugin_regionName
geoplugin_currencyCode
geoplugin_currencySymbol
geoplugin_city
geoplugin_region
geoplugin_areaCode
geoplugin_dmaCode
geoplugin_countryCode
geoplugin_countryName
geoplugin_continentCode

12. IP-based geolocation
is imprecise.

13. The JavaScript geolocation API
provides more accurate
location information.

15. var map = L.map(document.getElementById("map"));
map.addLayer(L.stamenTileLayer("terrain"));
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(
function (pos) {
var lat = pos.coords.latitude;
var lon = pos.coords.longitude;
var acc = pos.coords.accuracy;
map.setView([lat, lon], 16);
L.circle([lat, lon], acc).addTo(map);
L.marker([lat, lon]).addTo(map);
},
function (err) {
console.warn("Error: " + err.message);
},
{enableHighAccuracy: true}
)
}

17. The Geolocation Privacy and
Surveillance Act proposes
guidelines for how location
Information can be used.

18. Distance Formulas
 Pythagorean Theorem
 Spherical Law of Cosines
 Haversine Formula
 Vincenty’s Formulas

19. Spherical Law of Cosines
d = R· arccos(sin φ1· sin φ2 + cos φ1· cos φ2· cos Δλ)

20. Use a minimum bounding
rectangle to narrow results.

21. MBR Coordinates
φ2 = arcsin(sin φ1· cos δ + cos φ1· sin δ · cos θ)
λ2 = λ1 + atan2(sin θ· sin δ· cos φ1, cos δ - sin φ1· sin φ2)

22. function distance($lat1, $lon1, $lat2, $lon2) {
$rLat1 = deg2rad($lat1);
$rLat2 = deg2rad($lat2);
$rLonDelta = deg2rad($lon2 - $lon1);
return WGS84_RADIUS * acos(sin($rLat1) * sin($rLat2) +
cos($rLat1) * cos($rLat2) * acos($rLonDelta));
}
function destination($lat, $lon, $bearing, $dist) {
$rLat = deg2rad($lat);
$rLon = deg2rad($lon);
$bearing = deg2rad($bearing);
$angDist = $dist / WGS84_RADIUS;
$lat2 = asin(sin($rLat) * cos($angDist) +
cos($rLat) * sin($angDist) * sin($bearing));
$lon2 = $rLon + atan2(sin($rBearing) * sin($angDist) * cos($rLat),
cos($angDist) - sin($rLat) * sin($lat2));
return [deg2rad($lat2), deg2rad($lon2)];
}

24. function bounds($lat, $lon, $dist) {
$lat1 = destination($lat, $lon, 0, $dist)[0];
$lon1 = destination($lat, $lon, 90, $dist)[1];
$lat2 = destination($lat, $lon, 180, $dist)[0];
$lon2 = destination($lat, $lon, 270, $dist)[1];
return [
min($lat1, $lat2), max($lat1, $lat2),
min($lon1, $lon2), max($lon1, $lon2)
];
}
$rect = bounds($_GET['lat'], $_GET['lon'], $_GET['radius']);
$query = "SELECT name, address, city, state, zip_code, latitude, longitude
FROM libraries WHERE latitude BETWEEN {$rect[0]} AND {$rect[1]} AND
longitude BETWEEN {$rect[2]} AND {$rect[3]}";
$result = $db->query($query);
while ($row = $result->fetch(PDO::FETCH_ASSOC)) {
$dist = distance($_GET['lat'], $row['latitude'], $row[’longitude']);
if ($dist <= $_GET['radius']) {
$libraries[] = $row;
}
}

25. MySQL has implemented some
of the Open Geospatial
Consortium’s spatial extensions.

26. Thanks for coming!
Questions?