You can use Google Maps to display the contents of a KML file. The easiest way to do so is to go to the Google Maps page (http://maps.google.com) and enter the URL of the KML file as though it were an address or other search term. Such a query results in the following URL:

http://maps.google.com?q={kml-url}

For example, feeding the KML for the bookstore map back into Google Maps, we get the following:

http://maps.google.com/maps?q=http:%2F%2Fmaps.google.com%2Fmaps%2Fms%3Ff%3Dq%26om%3D1%26ie%3DUTF8%26msa%3D0%26output%3Dnl%26msid%3D116029721704976049577.0000011345e68993fc0e7

I have found using Google Maps to be an incredibly useful KML renderer. First, you can test KML files without having access to Google Earth. Second, you can let others look at the content of KML files without requiring them to have Google Earth installed. You should be aware, however, of two caveats in using Google Earth to render KML:

You can now use Flickr to learn more about KML. Currently, although there’s no official documentation, you can refer to Rev. Dan Catt’s weblog entry to learn some of the details about getting KML out of Flickr:

http://geobloggers.com/archives/2007/05/31/flickr-kml-and-a-stroll-down-memory-lane/

The following KML feeds contain at most 20 entries. You have two choices about the format to use:

So, anywhere I write format=kml_nl, you can substitute format=kml.

When you are looking at these feeds, it’s helpful to remember that in addition to using Google Earth as a KML viewer, you can use Google Maps, which I find very convenient. Just drop the URL for the KML file into the search box for Google Maps, and you can have the KML file displayed in Google Maps. For instance, you can take the KML for the 20 most recent geotagged photos in Flickr, like so:

http://api.flickr.com/services/feeds/geo/?format=kml_nl

and drop it into Google Maps, which you can access here:

http://maps.google.com/maps?q=http:%2F%2Fapi.flickr.com%2Fservices%2Ffeeds%2Fgeo%2F%3Fformat%3Dkml_nl

Currently, you can get a KML feed for an individual user with this:

http://api.flickr.com/services/feeds/geo/?id={user-nsid}&format=kml_nl

For example, here’s the feed for Rev. Dan Catt:

http://api.flickr.com/services/feeds/geo/?id=35468159852@N01&format=kml_nl

You can get the KML feed for a group here:

http://api.flickr.com/services/feeds/geo/?g={group-nsid}&format=kml_nl

For example, here’s the KML feed for the Flickr Geotagging group:

http://api.flickr.com/services/feeds/geo/?g=94823070@N00&format=kml_nl

You can get KML feeds for a tag, such as flower:

http://api.flickr.com/services/feeds/geo/&tags=flower&format=kml_nl

You can get KML feeds for locations. Here are some examples:

Note that the last two links are both for Beijing (北京).

You can do a combined search on a user, location, and tags. For example, to get Raymond Yee’s photos in Berkeley, California, tagged with flower, use this:

http://api.flickr.com/services/feeds/geo/us/ca/berkeley/?id=48600101146@N01&tags=flower&format=kml_nl

	Caution
	Look for official documentation on KML in Flickr to see how it evolves beyond its early beginnings.

The previous KML document defined a specific point for positioning the placemark’s name and icon but did not specify a viewpoint for the placemark. Given that you can zoom around the virtual globe from many angles, you won’t be surprised that KML allows you to define a viewpoint associated with a placemark. There are two ways to do so: the <LookAt> element and the <Camera> element (defined in KML 2.2 and later). You will find excellent introductory documentation for these two elements here:

http://code.google.com/apis/kml/documentation/cameras.html

Here I use a series of examples to illustrate the central difference between <LookAt> and <Cam era>: <LookAt> specifies the viewpoint in terms of the location being viewed, whereas <Camera> specifies the viewpoint in terms of the viewer’s location and orientation. I have gathered the examples in a single KML file:

http://examples.mashupguide.net/ch13/berkeley.campanile.evans.kml

which you can view through Google Earth or Google Maps here:

http://maps.google.com/maps?f=q&hl=en&geocode=&q=http:%2F%2Fexamples.mashupguide.net%2Fch13%2Fberkeley.campanile.evans.kml&ie=UTF8&ll=37.872507,-122.257565&spn=0.006581,0.01133&z=17&om=1

or here:

http://tinyurl.com/38oawy

I recommend loading the KML into Google Earth and in Google Maps so that you can follow along. See Figure 13-3 for how this KML file looks in Google Maps. Notice that there are three <Placemark> elements for two buildings: the Campanile, which sits almost due south of Evans Hall, and Evans Hall, both on the UC Berkeley campus.

Figure 13.3. KML for the Campanile and Evans Hall in Google Maps

<Placemark id="Campanile">
  <name>Campanile</name>
  <description><![CDATA[Campanile viewed from the South, using  <LookAt> (range=200, 
tilt=45, heading=0)]]></description>
  <LookAt>
    <longitude>-122.257704</longitude>
    <latitude>37.8721</latitude>
    <altitude>0</altitude>
    <altitudeMode>relativeToGround</altitudeMode>
    <range>200</range>
    <tilt>45</tilt>
    <heading>0</heading>
  </LookAt>
  <Point>
    <coordinates>-122.257704,37.8721,0</coordinates>
  </Point>
</Placemark>
            

Figure 13.4. View of the Campanile in Google Earth defined by the <LookAt> element

<Placemark id="Evans">
  <name>On the roof of  Evans Hall  Looking at Campanile</name>
  <description><![CDATA[Looking south from Evans to Campanile, using <Camera>  
(heading=180,  tilt=90, roll=0)]]></description>
  <Camera>
    <longitude>-122.2578687854004</longitude>
    <latitude>37.87363451913904</latitude>
    <altitude>50</altitude>
    <altitudeMode>relativeToGround</altitudeMode>
    <heading>180</heading>
    <tilt>90</tilt>
    <roll>0</roll>
  </Camera>
  <Point>
    <coordinates>-122.2578687854004,37.87363451913904,0</coordinates>
  </Point>
</Placemark>
            

Figure 13.5. View of the Campanile in Google Earth defined by the <Camera> element

Figure 13.6. View of the Campanile in Google Earth defined by the <Camera> element with a 45-degree roll

You can find documentation of the COM interface to Google Earth here:

http://earth.google.com/comapi/index.html

The following is a small sample Python snippet (running on Windows with the Win32 extension) to load the previous KML example, highlight each of the placemarks, and render their respective views in turn. Note that the code uses the OpenKmlFile method to read a local file so that it can then get features using the GetFeatureByHref method.

# demonstrate the Google Earth COM interface
# 
import win32com.client
ge =  win32com.client.Dispatch("GoogleEarth.ApplicationGE")

fn = r'D:/Document/PersonalInfoRemixBook/examples/ch13/berkeley.campanile.evans.kml'
ge.OpenKmlFile(fn,True)

features = ['Campanile', 'Evans', 'Evans_Roll']

for feature in features:s
    p = ge.GetFeatureByHref(fn + "#" + feature)
    p.Highlight()
    ge.SetFeatureView(p,0.1)
    raw_input('hit to continue')
            

The following is a Python code example to demonstrate the use of SetCameraParams to set the current view of Google Earth. Notice how the parameters correspond to those of the <LookAt> element. At some point, perhaps, the Google Earth COM interface will support the parameters corresponding to the <Camera> element in KML.

# demonstrate the Google Earth COM interface
# 
import win32com.client
ge =  win32com.client.Dispatch("GoogleEarth.ApplicationGE")

# send to UC Berkeley Campanile
lat = 37.8721
long = -122.257704

#altitude in meters
altitude = 0

# http://earth.google.com/comapi/earth_8idl.html#5513db866b1fce4e039f09957f57f8b7
# AltitudeModeGE { RelativeToGroundAltitudeGE = 1, AbsoluteAltitudeGE = 2 }
altitudeMode = 1  

#range in meters; tilt in degrees, heading in degres
range = 200
tilt = 45
heading = 0 # aka azimuth

#set how fast to send Google Earth to the view
speed = 0.1

ge.SetCameraParams(lat,long,altitude,altitudeMode,range,tilt,heading,speed)
            

In Mac OS X, you would use AppleScript to control Google Earth or something like appscript, an Apple event bridge that allows you to write Python scripts in place of AppleScript:

http://appscript.sourceforge.net/

Here’s a little code segment in AppleScript to get you started—it will send you to the Empire State Building:

tell application "Google Earth"
  activate
  set viewInfo to (GetViewInfo)
  set dest to {latitude:57.68, longitude:-95.4, distance:1.0E+5,
tilt:90.0, azimuth:180}
  SetViewInfo dest speed 0.1
end tell
            

This moves the view to 57.68 N and 95.4 degrees W.

Using appscript, the following Python script also steers Google Earth in Mac OS X:

#!/Library/Frameworks/Python.framework/Versions/Current/bin/pythonw
from appscript import *
ge = app("Google Earth")
#h = ge.GetViewInfo()
h = {k.latitude: 36.510468818615237, k.distance: 5815328.0829986408,
k.azimuth: 
10.049582258046936, k.longitude: -78.864908202209094, k.tilt:
3.0293063358608456e-14}
ge.SetViewInfo(h,speed=0.5)