So where do you begin? Google Building Maker was released yesterday for 50 cities, including Philadelphia.

Google is offering up Web-based tools to citizens that would help move forward the company’s ambitious plans to have 3D representations of every building in the world.

Philadelphia is one of 50 cities worldwide and just 21 in the United States that are part of the first wave of Google Building Maker, as the program was described in a company release from yesterday. Building Maker is a way to create geo-located 3D models of buildings that would be visible in Google Earth, with the intention of creating an impressively detailed Web atlas, though criticism already surrounds, as always, the heavy reliance on free citizen labor.

After navigating to Building Maker on a computer with the latest version of Google Earth installed, the user chooses any building from one of those 50 cities where modeling is currently possible, a total that also includes Atlanta, Seattle, Denver, San Francisco and Chicago. Whether the building already been created or not, the user matches Google’s ‘smart blocks’ to create the most accurate representation of the structure, as seen from Google-offered images taken from a variety of different aerial angles.

When those blocks are matched with the building’s images, Building Maker generates a photo-textured 3D model of that building for Google Earth. If the user deems his model worthy enough, it can be saved online in the Google 3D Warehouse, to be reviewed for use in Google Earth, where, if approved, it would appear in the 3D Buildings layer with a credit given. Users need a Gmail account to submit to the warehouse.

Naturally, some of the dialogue has already circled around a common complaint of crowdsourcing: free labor. Google is creating an awe-inspiring, interactive Web atlas — allowing anyone with highspeed Internet to see every corner of a Center City highrise — but is intending on doing so with a great deal of help from its user base.

Nick Zangara was 21-years-old in 2004 when a makeshift bomb exploded near his convoy in Tikrit, 90 miles northwest of Baghdad and a universe from his home in Northeast Philadelphia.

The George Washington High School graduate is one of at least 16 people from Philadelphia who have been killed in Middle Eastern military conflicts this decade, according to a new Google Earth layer called “Map the Fallen.”

“This Memorial Day I would like to share with you a personal project of mine that uses Google Earth to honor the more than 5,700 American and Coalition servicemen and women that have lost their lives in Iraq and Afghanistan,” writes Sean Askay, the layer’s creator. “I have created a map for Google Earth that will connect you with each of their stories, you can see photos, learn about how they died, visit memorial Web sites with comments from friends and families, and explore the places they called home and where they died.”

The layer, which made its national debut yesterday on CNN, is the four-year work of a geospatial content developer for the Google Earth Outreach team.

You must  have Google Earth 5.0 installed to view and download the project, which you can do here.

The layer creates a direct line from each service member’s hometown and his or her place of death. It works on a timeline system, showing each U.S. and coalition troop death chronologically, dating back to the first in Afghanistan on October 10, 2001. Users can search fallen service members by name, age, gender, hometown or location of death.

The 16 Philadelphians who have died range in age from 20 to 36 — Nick Zangara being among the youngest.

A Zangara Memorial Fund was created, though a listed e-mail was no longer functioning.