2. Lucio Grenzi
l.grenzi@gmail.com – Freelance
2
Who am I?
• Delphi developer for 11 years
• Now freelance and Web developer
• Javascript addicted
Nonantolando.blogspot.com
https://plus.google.com/108943068354277861330
http://it.linkedin.com/pub/lucio-grenzi/27/2bb/2a
3. Lucio Grenzi
l.grenzi@gmail.com – Freelance
3
Agenda
• HTML 5 and geolocalization
• GeoDjango: first introduction
• GIS data format troubles
• GeoDjango api's
• GeoDjango and Google Maps /
OpenStreetMaps
8. Lucio Grenzi
l.grenzi@gmail.com – Freelance
8
HTML 5 and Geolocation
• Supported by IE 9,
Firefox, Safari, Chrome
• All the smartphone has a
GPS or a Wifi network
card
• Location based services
9. Lucio Grenzi
l.grenzi@gmail.com – Freelance
9
HTML 5 Geolocation api's
geolocation.getCurrentPosition(showPosition)
geolocation.watchPosition(showPosition)
10. Lucio Grenzi
l.grenzi@gmail.com – Freelance
10
GetCurrentPosition
Example of requesting a potentially cached position.
// Request a position. We accept positions whose age is not greater than 10 minutes. If the user
// agent does not have a fresh enough cached position object, it will automatically
// acquire a new one.
navigator.geolocation.getCurrentPosition(successCallback,
errorCallback,
{maximumAge:600000});
function successCallback(position) {
// By using the 'maximumAge' option above, the position object is guaranteed to be at most 10
// minutes old.
}
function errorCallback(error) {
// Update a div element with error.message.
}
11. Lucio Grenzi
l.grenzi@gmail.com – Freelance
11
watchPosition
function getLocationUpdate(){
if(navigator.geolocation){
// timeout 60 seconds
var options = {timeout:60000};
watchID = navigator.geolocation.watchPosition(showLocation,
errorHandler,
options);
}else{
alert("Sorry, browser does not support geolocation!");
}
}
13. Lucio Grenzi
l.grenzi@gmail.com – Freelance
13
GeoDjango
GeoDjango intends to be a
world-class geographic Web
framework.
Its goal is to make it as easy
as possible to build GIS Web
applications and harness the
power of spatially enabled
data.
16. Lucio Grenzi
l.grenzi@gmail.com – Freelance
16
Geospatial libraries
Program Description Required Supported Versions
GEOS Geometry Engine
Open Source
Yes 3.3, 3.2, 3.1, 3.0
PROJ.4 Cartographic
Projections library
Yes (PostgreSQL and
SQLite only)
4.7, 4.6, 4.5, 4.4
GDAL Geospatial Data
Abstraction Library
No (but, required for
SQLite)
1.8, 1.7, 1.6, 1.5, 1.4
GeoIP IP-based geolocation
library
No 1.4
PostGIS Spatial extensions for
PostgreSQL
Yes (PostgreSQL
only)
1.5, 1.4, 1.3
SpatiaLite Spatial extensions for
SQLite
Yes (SQLite only) 3.0, 2.4, 2.3
17. Lucio Grenzi
l.grenzi@gmail.com – Freelance
17
PostGIS 2.x
• Completely rewritten
• Many more vector functions including
• Django support >= 1.5
• Suggested PostgreSQL >= 9.2
18. Lucio Grenzi
l.grenzi@gmail.com – Freelance
18
GIS problems
• The Earth is not like
a ball!
• How to store data
efficiently
– Different vendor
implementation
20. Lucio Grenzi
l.grenzi@gmail.com – Freelance
20
GDAL : “swiss army knife” of GIS data
• Geospatial Data Abstraction Library
• A subset of GDAL is specialized in reading and
writing vector geographic data in a variety of
standard formats
• GeoDjango only supports some of the
capabilities
21. Lucio Grenzi
l.grenzi@gmail.com – Freelance
21
GEOS
• Geometry Engine - Open Source
• GEOS implements the OpenGIS Simple
Features for SQL spatial predicate functions
and spatial operators.
• GeoDjango implements a high-level Python
wrapper for the GEOS library
22. Lucio Grenzi
l.grenzi@gmail.com – Freelance
22
GEOIP
IP-based geolocation binding MaxMind
• Needed in order to perform IP-based
geolocation( the location, coords)
• requires the GeoIP C library and GeoIP
Country or City datasets
36. Lucio Grenzi
l.grenzi@gmail.com – Freelance
36
GeoDjango & Google Maps: recipe
• Web server
• Python and GeoDjango
• PostgreSQL (postgresql-9.1-postgis)
• libgeos
38. Lucio Grenzi
l.grenzi@gmail.com – Freelance
38
Step 2 : Geospatial information
• Edit model.py in order to setup the spatial
reference system
• Google Maps api use srid = 4126
name = models.CharField(max_length=32)
geometry = models.PointField(srid=4326)
objects = models.GeoManager()
40. Lucio Grenzi
l.grenzi@gmail.com – Freelance
40
Get Current position
<script language="javascript">
var lat=50;
var lon=-110;
function load() {
if (GBrowserIsCompatible()) {
var map = new GMap2(document.getElementById("map"));
map.setCenter(new GLatLng(lat, lon), 13);} }
function map(position) {
lat = position.coords.latitude;
lon = position.coords.longitude;
load(); }
function get_location() { navigator.geolocation.getCurrentPosition(map);}
</script>
41. Lucio Grenzi
l.grenzi@gmail.com – Freelance
41
Record Location
class RecordLocation(webapp.RequestHandler):
def post(self):
session=SessionManager(self)
if session.is_set():
marker=Markers(lat=self.request.get('lat'),lon=self.request.get('lon'),user_id=self.request.get('user')
)
marker.put()
self.response.out.write('<html><body>')
self.response.out.write(" Location Updated<br/>")
self.response.out.write('</body></html>')
42. Lucio Grenzi
l.grenzi@gmail.com – Freelance
42
Generate Marker
class GenerateMarkers(webapp.RequestHandler):
def get(self):
session=SessionManager(self)
if session.is_set():
markers=db.GqlQuery("SELECT * FROM Markers")
doc='<?xml version="1.0"?>'
doc+='<markers>'
for marker in markers:
doc+='<marker '
doc+='lat="'+marker.lat+'" '
doc+='lon="'+marker.lon+'" '
doc+='type="restaurant" '
doc+='/>'
doc+='</markers>'
self.response.out.write(doc)
43. Lucio Grenzi
l.grenzi@gmail.com – Freelance
43
Openlayer
<html>
<head>
<script src="http://openlayers.org/api/OpenLayers.js"></script>
<script> var points = []; </script>
<ul>
{% for point in interesting_points %}
<li>{{ point.name }} -- {{point.interestingness}}</li>
<script>points.push({{point.geometry.geojson|safe}});</script>
{% endfor %}
</ul> </scrpit>
</head>
<body onload="init()">
Intersting Points.<br />
<div id="map"></div>
</body></html>
44. Lucio Grenzi
l.grenzi@gmail.com – Freelance
44
Openlayer js script
<script type="text/javascript">
var map, base_layer, kml;
function init(){
map = new OpenLayers.Map('map');
base_layer = new OpenLayers.Layer.WMS( "OpenLayers WMS",
"http://labs.metacarta.com/wms/vmap0", {layers: 'basic'} );
var vectorLayer = new OpenLayers.Layer.Vector("Simple Geometry");
var point = new OpenLayers.Geometry.Point(-100.01, 55.78);
var pointFeature = new OpenLayers.Feature.Vector(point,null,null);
map.addLayer(vectorLayer);
map.setCenter(new OpenLayers.LonLat(point.x, point.y), 5);
vectorLayer.addFeatures([pointFeature]);
}
</script>
45. Lucio Grenzi
l.grenzi@gmail.com – Freelance
45
Openlayer django script
vectors = OpenLayers.Layer.Vector("Simple Geometry");
for (var i = 0; i < points.length; i++) {
point = format.read(points[i])[0];
point.attributes = {'type':'point'};
vectors.addFeatures(point);
}
