Philadelphia Reflections

Geo Positioning

Geo Tagging refers to adding latitude and longitude information to websites and photographs. This has been around for a long time but it has taken the advent of Google Earth for it to really start to catch on.

This blog entry has geo meta tags that you can see if you look at the HTML source ("View > [Page] Source"). The input was as follows:

Address: 82 Devonshire St Boston MA

Lat: 42.3578 Lon: -71.0577

Descriptive Place Name: Fidelity Investments headquarters

Region: US-MA Country Code: US Country Name: United States

This creates meta tags in the HTML Header as follows:

<!-- geo tags for 82 Devonshire St Boston MA -->
<meta name="ICBM"          content="42.3578, -71.0577" />

<meta name="geo.country"   content="US" />
<meta name="geo.region"    content="US-MA" />
<meta name="geo.placename" content="Fidelity Investments headquarters" />
<meta name="geo.position"  content="42.3578; -71.0577" />

<meta name="tgn.name"      content="Fidelity Investments headquarters" />
<meta name="tgn.nation"    content="United States" />

• To be precise you can go to the location with a GPS device and record the exact coordinates.
  (see below for a discussion of GPX, the GPS transfer protocol)
• Google Earth is a very good way to find coordinates of any spot on earth
  and both GE itself and the KML Editor will allow you to pick up coordinates from GE.
• You can find the lat and lon of a US address using GeoURL Header Generator
• My Geo Position can also be helpful
  
  
• But for most lookups, the easiest method is to use the Firefox Sidebar AddOn called Minimap; it's right in your browser so you don't have to switch back and forth. (The AddOn download is found here: Mini Map Sidebar).

The Region, Country Code and Country Name can be found here: ISO-3166-1 Country Names

geo.placename and tgn.name are often rendered as the city name but are intended to describe the geographical feature ("Pyramids of Giza" or something). This tag is optional.

HTML geo meta tags can be validated here:

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There is a search engine of long standing that reads HTML geo meta tags and indexes the website based upon its location; for searching, it groups sites based on their geographic proximity: GeoURL.

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Photographs can also contain geo meta data, so-called EXIF data (Firefox has an EXIF viewer AddOn).

JPEG is the most common image format and the easiest to deal with. The combination of Picassa2 and Google Earth allow you easily to add this information to your own photos.

The process of adding lat and lon to your photographs is this:

1. Select one or more photos in Picassa
2. Select Tools > GeoTag > GeoTag with Google Earth ...
3. This starts Google Earth and you can "fly" to the location of the picture

4. A small Picasa window will appear in Earth's lower-right corner displaying thumbnails of the pictures you selected; press the "Geotag" button.
5. When all of your pictures are tagged, press the "Done" button

Slowly, camera manufacturers are providing GPS capability. Some few have GPS devices built in and some others allow an external GPS device to be attached, although both Canon and Nikon are way behind the curve ... if you own either, you can essentially forget it: the best - lousy - solution is to carry around a GPS with you and synchronize the times ... ugly.

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The Google Maps API allows maps to be embedded in a website as is done here. Google Maps API

The JavaScript required to embed the map on this page can also be seen in the HTML source ("View > [Page] Source"). In addition to JavaScript, you need a DIV with an ID of "map" or whatever is specified in the JavaScript document.getElementById entry, which specifies the height and width of the map to be displayed.

To embed these maps you must register with Google

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In addition, there are extensions to ATOM and RSS to include lat and lon in your syndication feeds; there are three standards that I have found: GeoRSS (ATOM example) , W3C Geo (RSS example) and an "ICBM RSS Module". This website extends the namespaces of both its ATOM feed and its RSS feed to include all the tags.

Google, Yahoo and Microsoft all now support GeoRSS as a feed to their map programs. My sense of it is that KML is a richer protocol, allowing more features, but fundamentally all these XML variants do mostly the same thing.

Google Sitemaps can include links to KML files (and ATOM, now, too). Part of the sitemap generation on this site is some code that picks up every *.kml and *.kmz file in the /kml/ folder and adds them to our sitemap.xml file.

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Google Earth is filled with delights, not the least of which is a Flight Simulator! Google Earth Flight Simulator Keyboard Controls

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KML ( Keyhole Markup Language, Keyhole being the predecessor to Google Earth) is an XML protocol that allows you to incorporate Google Earth into graphical presentations. Google KML Overview

Google Earth Outreach helps you get started: Google Earth Outreach

An extraordinary collection of KML files you can view is found here: Spectacular satellite images of the world

I found a KML editor here: NorthGates' KML Editor for Windows. It's rudimentary but very handy for what it does do.

Here's the Google Earth tools list where I found the KML editor: EarthPlot Software Tools For Google Earth

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The way we serve the KML in the link that connects to Google Earth from individual blogs uses the following PHP script as its base:

<?php

// See Google Earth's KML 2.1 Reference
// https://code.google.com/apis/kml/documentation/kml_tags_21.html

$lat			= $_GET['lat'];
$lon			= $_GET['lon'];
$placename		= $_GET['placename'];
	
$altitude		= $_GET['altitude'];
$range			= $_GET['range'];
$heading		= $_GET['heading'];
$tilt			= $_GET['tilt'];
	
if ($altitude	== NULL) {$altitude	= 0;}
if ($range	== NULL) {$range	= 1000;}
if ($heading	== NULL) {$heading	= 0;}
if ($tilt	== NULL) {$tilt		= 0;}
	
$description	= "<h3><font color=\"#ea9f20\"><a href=\"https://www.philadelphia-reflections.com/\">
		PHILADELPHIA REFLECTIONS</font></a></h3>
		<p>The musings of a Philadelphia physician who has served the community for six decades.</p>";
	
	
header('Content-Type: application/vnd.google-earth.kml+xml');
header('Content-Disposition: inline; filename="philadelphia-reflections.kml"');

echo '<?xml version="1.0" encoding="UTF-8"?>'; 

?>

<kml xmlns="https://earth.google.com/kml/2.0">

  <Placemark>
    <name><?php echo $placename; ?></name>
    <description>
        <![CDATA[<?php echo $description; ?>]]>
    </description>
    
    <LookAt>
      <longitude><?php echo $lon; ?></longitude>
      <latitude><?php echo $lat; ?></latitude>
      
      <altitude><?php echo $altitude; ?></altitude>
      <range><?php echo $range; ?></range>
      <tilt><?php echo $tilt; ?></tilt>
      <heading><?php echo $heading; ?></heading>
      
      <altitudeMode>relativeToGround</altitudeMode>
    </LookAt>
    
    <Point>
      <coordinates><?php echo "$lon,$lat,$altitude"; ?></coordinates>
    </Point>
    
  </Placemark>

</kml>

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Of course, GPS devices are an integral part of this process of Geo Positioning. GPS devices are supposed to support the open-source protocol GPX,
which is an XML-based description of waypoints and routes. Wikipedia describes GPX here: GPS eXchange Format

The GPX protocol's official website is here: GPX The GPS Exchange Format

Google Earth supports raw GPX (File > Open ...) and when you open a GPX file in Google Earth, it converts it to KML. But if you want stand alone programs to do this:

• Convert from GPX to KML: GPS to Google Earth KMZ / KML converter
• Convert from KML to GPX: Google Earth KMZ / KML to GPS converter

If you have non-standard GPS data, you may want to have a look at GPS Babel for conversion of native GPS formats as well as the GPS Utility and G7ToWin

A nice blog on these things relative to Google Maps is here: Using XSL to Transform Google Earth (KML) and GPX to Google Maps API

At Philadelphia Reflections, we are creating tours by carrying a GPS and a camera around on our travels. The GPS track becomes a path and waypoints become placemarks. When you come home, download the GPS data in GPX format and open up the GPX file in Google Earth. Use Google Earth to edit the placemark balloons, including pictures and text.

Example of a GE tour made with a GPS (Garmin eTrex Vista HCx)

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There are many, many sightseeing blogs around that take you to interesting places on Google Maps and Google Earth. A place to start looking is Sightseeing with Google Satellite Maps

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Somehow, the concept of "mashup" is related to all of this but it sort of sounds like the term "multimedia" a few years ago ... fancy in concept but somewhat vague in reality.

Google has a Mashup Editor and Wikipedia has a definition but it's not clear what it all adds up to.

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(my thanks to https://centricle.com/tools/html-entities/ for HTML encoding)

Originally published: Saturday, September 22, 2007; most-recently modified: Monday, June 04, 2012