Google Earth Lessons

An Educational Resource for Teachers

Photo Immersion with the PhotoOverlay Creator!

You have probably seen those cool GigaPixl and GigaPan photos in Google Earth. They are pictures that you can immerse yourself in and explore instead of just looking at in a balloon. Students are fascinated by them, and therefore you can use that interactivity and interest to inspire students to more fully immerse themselves in your particular topic!

Thanks to the folks at University College London Centre for Advanced Spatial Analysis as presented through ‘Digital Urban’, you can now create your own really cool immersive photo overlays inside Google Earth! (All Platforms - Windows, Linux, Mac, Google Earth 4.2x and Java required)

final product

Quick Jump:
Download PhotoOverlay Creator
Tutorial on PhotoOverlay Creator
Adjusting the Heading
Preparing to Share via email or WebLink (smallish files)
Preparing to share huge files via the web or email.
Lesson Integration Ideas
Sample Files – Single 4 Megapixel photograph kml - kmz (576K, works on Windows), panorama stitched from two photos kml - kmz (1M, works on Windows), Cylinder created from extra wide angle lens photo kml - kmz (762K works on Windows)

Getting Started

The software is remarkably easy to use, but at this writing (October 2007) there are a couple tricks to make it a bit easier and to allow you to customize your final product. Distribution to students is also an issue we will explore below.

The first thing you will need is a digital picture. Any picture will do, but the larger it is, the more interaction your students will have. For the samples I used some shots that I took with my once very nice 4 MegaPixel Olympus digital camera. If you have access to a nice 5-10 Megapixel digital SLR your results will be even better. In theory you could even scan a picture and choose a super high resolution (700+ dpi) jpg output too if you wished.

Another option is to create a panorama from a series of photographs. There are zillions of options, most costing a fair amount of money ($100+ US). One free alternative for creating panoramas from existing photos is a series of applications called ‘hugin’ available at http://hugin.sf.net There are Mac, Windows and Linux versions available. No matter what you use to create your panorama, the end product will have more depth (due to its bigger size) than a single photo.

So, once you have your picture it is time to get to work.

Step 1. For ease of workflow, you will want to have your photo in its own separate folder as Photo Overlay Creator creates all the support files Google Earth needs and if you have your picture in its own folder, then you don’t have to go hunting for them.

Step 2. Visit http://www.casa.ucl.ac.uk/software/photooverlaycreator.asp and download the latest version of the Photo Overlay Creator software. The software comes as a .zip file, so you will need to unzip it when the download is complete. Make sure to unzip it into its own folder so you don’t have the files all laying around.

Step 3. Inside the unzipped folder you will find three files.

contents of folder

Double click on the .BAT file or the .jar file to launch the PhotoOverlay Creator. Click – File:Open File… and direct it to the folder where you have your cool picture patiently waiting.

open

In a second you will see your picture displayed in the main window. If that is the picture you want to use, click the Create button.

create

Step 4. Now this is where it gets just a tiny bit tricky. The software will only accept longitude and latitude in decimal format, so you need to set up Google Earth to show only the Decimals. So open and switch to Google Earth, click the Tools Menu and pull down to Options.

options

In the window that appears, choose the 3D View tab and select ‘Decimal Degrees as illustrated below and click OK.

degrees

Now, still in Google Earth, find where you want your picture to appear and hover the hand cursor over the spot and jot down the longitude and latitude coordinates out to the 6th decimal place (example: 51.521999).

coordinates

Step 5. Switch back to PhotoOverlay Creator and enter the longitude and latitude into the appropriate boxes. In the Description box you can type anything you want that will help your students. The Image Shape choice you make will depend on the picture you have and how you want it displayed. For just a regular picture you will want ‘Rectangle’.

data window

If you created a circular (or partly circular) panorama (180 – 360 degrees) that you stitched together into a single picture, choose ‘Cylinder’. If you are super fancy and did one of those zillion picture or FishEye full 360 top to bottom Quicktime VR sort of panoramas then choose ‘Sphere’. Most of us will use Rectangle though. Once you have everything the way you want, click OK, then ‘Start’.

start

It will crunch for a moment, depending on how big the picture was, and then click ‘Finish’.

Step 6. Appearing in the same folder as your picture, you will now find two new items: a folder that contains your sliced and diced picture, and the Google Earth .kml file that puts the tiles back together when viewed in Google Earth!

files

You can click on the .kml file and Voila’ there is you picture! How cool is that?! But wait… there is more to the story…

Warning: This is the kind of geeky stuff.

At this point, you have a workable picture that is inside of Google Earth, and if that is all you needed you are free to go. You can copy the whole folder to a CD, USB drive, Network Folder, whatever, and off you go. NOTE: Only move the overlay to “My Places” from ‘Temporary Places” if the folder containing all the files is in its final resting spot though, otherwise the overlay won’t work any more since Google Earth won’t know where you have moved them and will give you no end of annoying error messages when you try to activate it.

If, on the other hand, you want to adjust how the picture appears in Google Earth, distribute the files via the internet (web or email) or over a school network then you will want to keep reading…

Adjusting the Heading…

One of the comments that a user posted at Digital Urban noted that there was no way in PhotoOverlay Creator to adjuct the heading of the picture. What that means is adjusting the photo so that it appears where the camera was pointing. To fix that you will need to do some adjustments inside Google Earth.

Step 1. Open the container that contains the actual picture placemark by clicking the + sign by the icon that appeared when you opened the .kml file in Google Earth.

plus

properties

In the window that appears, select the ‘Photo’ tab. Use the sliders to adjust any number of settings.

settings

It can be a little confusing at first since the picture covers Google Earth, making it difficult to get the heading perfect the first time, but play around with it a while and you will most likely end up with a result you are happy with.

Step 2. Once you have made your modifications and are happy with them, right click on the container (the blue and white icon) and pull down to ‘Save as…’ overwriting the existing file, or renaming it and keeping the original.

save

Preparing to Share via email or Web Link (for smallish pictures)

If you were to attach the .kml file to an email or post it on your class web page, guess what. It won’t work. That is because the .kml file is just a pointer to the folder of tiles which is sitting somewhere on your computer. In order to distribute it, you will need to turn the .kml file and folder into a .kmz file first, and then you can distribute it.

The thing is that it depends on how big your original picture was. If it is a huge file (bigger than 2 megabytes or so, depending on your situation), you will need to skip to the next section. If it is a smallish picture, file size-wise you can can do the .kmz trick.

Step 1. Edit the .kml file to point to itself. This one caused me no end of frustration and seems to only work for Windows, if you are on an Apple or a Linux computer you will have to test it out to see which works. Ultimately what you are going to do is 'zip' all the files together into a single container. For Windows, when Google Earth downloads a kmz file it puts it in a temporary folder buried deep in your computer. You need to change the .kml code before you zip it up (see instructions for zipping it up below) so that Google Earth knows where to find the folder of pictures.

Simply open the .kml file with a text editor, such as Notepad, and look for the line of code that begins with <HREF> and references the folder of pictures as below:

<Icon>
<href>your_photos_name-tiles/your_photos_name_$[level]_$[x]_$[y].jpg</href>
</Icon>

Then enter the what you are going to name your file, followed by .kmz, before it, like so:

<Icon>
<href>
your_photo.kmz/your_photos_name-tiles/your_photos_name_$[level]_$[x]_$[y].jpg</href>
</Icon>

Save the file, making sure your text editor doesn't change the file name from .kml to .txt. Again, this trick works on Windows for sure. On a Mac or Linux you might either not have to do this, or it just plain won't work, I honestly don't know since I don't haveeither to test it out with. If you test it and find out, please let me know!

Step 2. Add the .kml file and the folder to a zip archive.

This is a tough one to explain, simply because there are so many ways to create a .zip archive. If you know how, skip to step 2. If you don’t know how, well, where to start…

A zip archive essentially smooshes files down by getting rid of blank spots in the guts of the files and finding repeating patterns of code. It is a complex process that has been super simplified thanks to all sorts of software. You might be familiar with some of them. The most popular ones are WinZip and WinRAR although there are a ton of free alternatives, like 7zip (Mac users can use commercial product Stuffit). With WinRAR, my personal favorite, it is simple. After WinRAR is installed you just right click on the files you want and choose ‘Add to Archive’

add

Check the ZIP extension and click OK.

zip

Quick and easy!

Step 3. Rename the file from .zip to .kmz

kmz

If Windows whines at you just click Yes.

sure

Step 4. Distribute the .kmz file as an email attachment or as a web link! Be sure to note the size of the file though. Many email systems have size restrictions and if the file is too big you will overload the recipient’s mailbox. Also, if the person you are sending the file to has a dial up connection it could take forever for them to download. If it is for the web, such as a class home page, be cognizant of the bandwidth use for the file. If you have a slow network, half the class time could be spent simply opening your neat picture.

Preparing to share huge files via the web or email.

Up until now, we have been looking at relatively small files. But what if you have a HUGE file? For instance, I used USAPhotoMaps to create a huge 26 Megabyte topographic jpg file of some terrain in Idaho for a lesson on geography. The .kmz file comes in at a whopping 29Mb! It is far too large for students to download or to email.  But, they don’t necessarily need the whole thing.

One neat aspect of the PhotoOverlay Creator is that it does create small tiles, thereby allowing only the needed sections of the picture to be served up.

If you are in that sort of situation, then the fix is simple. What you are going to do is place the .kml file and the tiles folder wherever you need them. This could be a class website, or a network drive that is mapped uniformly to the student’s workstation.

For instance, in my school when a student logs in to a Windows computer a drive U:\ is auto-magically mapped to the computer, so students can access class files or save to their folders which reside there. If you are in a similar situation, the only real trick is to make sure that the folders leading to the tile folder don’t have any spaces in the names. (Ex: U:\Lesson_files\GoogleEarth\overlay\my_picture.kml) Then follow the .kml editing step below and everything should work fine, depending on your network’s robustness and friendliness.

Like with mapped network folders, the same admonition about no spaces or special characters in the file and folder names holds true. Simply edit the .kml file, upload the tiles folder and the kml file to your web server and you should be good to go.

To edit the .kml file, open a text editor, such as NotePad, and use it to open the .kml file being sure to choose ‘All files..’ so that you can see the .kml file.

all

Once the file is open, you are going to look for the <HREF> pointer to the tiles folder.

code

It is in front of the folder name that you are going to type your path or URL.

url

Save the file as .kml and you are done!  Now you can distribute the small .kml file and users will still be able to see your neat picture, one bit at a time.

NOTE: Not all networks and web servers behave the same. The trick above will work for lots of network and web systems, but your mileage and frustration level may vary.

Lesson Integration Ideas

Here are just some ideas of how you can use the new tool for uses other than sharing nice vacation photos:

Compare and Contrast – What is different about the people, architecture, landscape in the picture compared to here, another picture of a different place.

Prediction – What do you think is about to happen to the man in the red hat? Where is the lady with the bags going?

Identify – Find three signs of past glaciation. Where would you most likely see a frog? Identify two places where the city has worked to control traffic flow. How many habitats can you find?

Story Starters – Imagine you are a cat sitting in the window of the white house. What could you tell about the people passing by? What changes might you have seen if the picture was taken 10 years ago?

Analysis – How might the rocks have gotten positioned in that manner? Why are the saplings under the tree instead of in the field?

Student Created Content – Place the overlay in the appropriate geographic location. Place the landforms in an area where you would most likely find them.

Use GIMP/PhotoShop/Graphics program to annotate an image for student use with arrows and captions, and such.

Jeepers, there is so much you can do! If you create a lesson based on this, let us know! Just email the details to david(AT)gelessons.com –substituting the (AT) for @ of course. Also, if you create some neat .kmz files, please upload them to the kmz bucket and we would be happy to serve them for you as long as they aren’t too huge.