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Google Earth Train Set

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Trying to understand the ways that a new transit line might be run through a neighborhood is somewhat difficult to do without understanding the measure of railways and specific streets.  And it is difficult to assess the practicality or impracticality of a scheme withour being able to represent the juxtaposition of these things in proper scale and also in the broad plan.  It is also very difficult to communicate complex imaginary ideas about places without perspective drawings. These difficulties have traditionally made it difficult for people without highly specialized skills to participate as equals in the discussion of urban design alternatives.  This Google Earth Train Set project provides a hint about how ordinary people may be able to explore and develop place-based ideas and to share and collaborate on creative urban design problems using free and easy-to-use tools such as Google Earth.


Viewing a Presentation

The context of this demonstration is the impending extension of a urban light rail project, Boston's Green Line, through East Cambridge to Medford and Union Square (all in Massachusetts, USA.)  There are several alterbatives involving moving a beloved trolley stop accross a large highway, or keeping the stop closer to the neighborhood, and running part of the extension as a streetcar in the highway itself.  Good ideas? bad ideas? It will be easier to see if you install google earth (free!) on your computer and follow these easy steps:


Download this KMZ File and follow the tips pictured below to quickly navigate in 3d to different points of view and looking at some comments. Once you see how this works, you will be able to explore any other perspective and to write your own commentary. If you think I got it wrong or if you have a better idea, show me! See notes below about how you can easily modify my schemes using the Google Earth Train Set!

Click the discussion links to zoom to a viewpoint and read some commentary. Add your own comments and points of view!

Click the button next to each scheme to zoom in and view the geometry of a particular proposal, 



Click the + next to a scheme to reveal more comments.  Double-clicking the comment will zoom to a new point of view.  Get into the city to see the impacts of different schemes in 3d!



How to Develop and Share your Own Ideas

The Google Earth User Guide provides good documentation for the fundamental techniques that will allow you to modify the train layout provided above or to create your own.  The basic Google Earth techniques you need to learn are as follows:

  • Create a new Folder & Snapshot Current View
  • Add a Placemark, Polygon or Path
  • Add and Georeference an Image Overlay

You can easily create copies of schemes in Google Earth by simply selecting, copying and editimng the prperties of exisating folders and featues in teh Google Earth Places panel.  Or if you would like to add items directly from my MBTA Greenline Kit of Parts, you can download it here: MBTA Green Line Kit A good place to start is to turn off all of the prepard trainset stuff and use the Add Image Overlay tool to georeference the Northpoint Plan Image to get an idea of how the place image overlay tool works, abd also to see where the new greenline station is plannned.

Building the Kit of Parts

There are a few ideas and resources that are also necessary for building the trainset.  I used the free Google 3d Editor -- Google Sketchup for some of this.  For all but building the Trolley Cars, you could use any image ediing tool.  The critial aspects of a railroad that we want to represent are: the width of the right of way; the length and width of a platform, and the minimum radius of a turn.  We also ended up represneting a typical Trolley Train in 3D; this will be discussed in a few paragraphs, below. 


The important reason to be fooling with this train set is to understand where a light rail corridor will fit and the issues of running it past all of the obstacles from end to end.  So we need to get the width turning radius right.  For the widths I measured some precendents on other parts of the system.  You can visit my precendent sites in the Misc folder of the sample KMZ file offered at the top of this page.  There is a handy ruler at the top of the google eath window and you can change its unites to whichever is most comfortable.



The width of a station is 40 feet, The witdh of a right of way is 30 feet, the length of a station platform is 250 feet.  Finding the turning radius was a little more difficult.  After searching iin (what else?) google, we eventually found a chat group of transit nuts where one fellow who seemed to know what he was talking about cited the minumum turning radius for an articulated modern trolley car as approximately 90 feet.  Starions have to be on straight track so that passengers don;t have to jump too far to get into the train.


After a little experimentation, it was found that the best way to represent the track segments in Google Earth was to place them as image overlays.  This allows us to stretch and twirl sections of track to fit them together and extend straight sections long diistances without distortion.  Since images are inherently rectangular, we need to use an image format like GIF or PNG that can handle transparency.  These images can be made using an image editing tool like your computer's free paint program.  The key thing is to get the proportions right.



  I chose to diagram my track sections in Google's 3d Editing Program, sketchup.  I measured the length of a chord on my curve section so that I can check to see that the proportions did not get distorted by my placement in Google Earth.  When I finisged the track sections, I put sketchup in Plan view and turned off perspective, then exported the scene as a exported as a PNG image.  I then used my paint program (actually, I used photoshop) to clip our the pieces, being careful to leave as little margin as possible.  Finaly, I made the buff background in the image the transparent color.  You can see the resulting images in the MBTA Greenline Kit, linked at the top of this section.


Making the Trolley Cars

This turns out to be a great introduction of the basic principals of using Sketchup. I won't try to duplicate the excellent Sketchup documentation here.  You may want to look at the first 12  video tutorials for sketchup for a very thorough treatment.  (wear headphones!)  You may also click the links for the procedures in the narrative below to view sketchup's help documentation for each step.


First I found a good shot of the top of a trolley in Google Earth and zoomed right down on it.  I used the Tools>Google Earth>Get Current View function in Sketchup to capture the georeferenced, scale image of the trolley!  I made a new layer in Sketchup named Trolley and used the Draw tool to outline one section of a trolley.  I was careful to use inferences to keep the dimensions of this box square.  I then used the Push-Pull tool to extrude the new polygon along the Blue Axis and entered the approximate right height into the Value Control Box.  I then opened one of my trolley images as a texture, and used the free pin mode to position the texture onto the apropriate face of the trolley section.  To get image of the top of the trolley, I unlocked the Google Earth Snapshot group, and made its image into a Projected Material, I then used the tools in the Materials Window, to apply this texture to the top of the trolley.  I then triple-clicked the trolley car to select all connected geometry, and made it a component.  I used the rotate tool, holding down the control key, to rorate a copy of the trolley, pivoting on the back corner.  Watching the Value Control Box to catch it at just 180 degrees.  Then I grabbed the other corner with the Move Tool and shifted the new section to align with the apropriate corner on the original.  There is your trolly model!


There are a couple of ways to turn your trolley into Google Earth.  The neatest way is to simply use the Place Model function in the Google Earth Tools.  This will place the model in its georeferenced location where you captured the footprint.  You mah now copy and paste this model into any folder in your Google Earth Places panel, and modify its location properties and drag it and rotate it wherever you want.  ANother useful thing to do, if you want a trolley that you can open from the Google Earth File menu and place wherever yoyu want, is to export the model as a .dae file (which actually ius a COLLADA file.  COLLADA is a communityy-based open standard for exchanging 3d models.  This model file can be saved, as we have done in our MBTA Greenline Kit.


 Where did the Buildings Come From?


Aha!  we thought you'd never ask!  Consult the Virtual City Collective Home Page for the full details.