Hi everyone!

A little while ago Erin D'Alessandro, at ESRI Canada sent everyone a link to a web site where you could see a really nice mosaic of images of the world from space at night.

Well, John Nicolucci, a teacher in Toronto, took it one step further and geo-referenced the image in ArcView - thanks John. Now, you can load the image in ArcView and overlay a map of the countries on top!

LRT has used her email instructions below as the basis and John's file plus the website image to create this instructional page. Teachers really do share. So enjoy this exercise with your students

Wayne Hamilton
IT Consultant
NS Dept of Education
Learning Resources & Technology
902 424-2451  fax 902 424-0633
Email: whamilto@istar.ca


In order to view the image and the countries, follow these steps:

1. Copy the image file (worldatnight.JPG) and the world file (worldatnight.JGW) to the SAME FOLDER on your hard drive.
    preferably your "GISdata" folder under a folder name such as "nightworld"

NOTE: the jpg will open as an image which you can right click and then "save image as" to your "gisdata\nightworld" folder.
            the jgw will open as a few lines of texts and numbers, copy these to a Notepad or Simpletext document . Then save the file as
            "worldatnight.jgw" to the SAME FOLDER "gisdata\nightworld"

            If all this sounds too difficult or you want the quick and easy solution as you have done this thousands of times, then just 
            download the file "nightworld.zip" and extract it to a folder.  Open the project "nightworld.apr" and go then to step 7 below

2. Start ArcView with a blank project.

3. From the File menu, choose Extensions. Put a check mark next to the JPEG (JIFF) Image Support extension. Click on OK.

4. Open a New View.

5. Click on the Add Theme button. At the bottom left of the dialog box, change the Data Source Type to Image Data Source.
    Navigate to the folder where your image is stored. Select it and then click on OK.

6. Turn on the visibility for the theme in your Table of Contents. Move your mouse over the image and notice how the latitude and longitude appear
     in the top right hand corner of ArcView!

7. Now for the fun part...Click on the Add Theme button again. Navigate to the ESRIDATA folder on your hard drive. Choose the World folder
    and then choose a country shapefile like country.shp or cntry95.shp (Oops! Make sure you change you Data Source Type back to Feature Data
    Source or you won't see the themes).

8. Turn on the visibility for the new theme in your Table of Contents. You should see the countries line up with the image underneath. Let's make an
    outline map so that we can see the image through the countries...

9. Double click on your country shapefile to bring up the Legend Editor. Make sure that the Classification Type is set to Single Symbol. Double click on the coloured square under Symbol, this will bring up your Fill Palette.

10. Click on the No Fill square (top left). Click on the Paintbrush icon to bring up the Colour Palette. From the drop down menu, choose Outline.     Choose a color for your outline (red works really well).

11. Click on Apply and close the Legend Editor. You should now have an outline map of the countries sitting on top of the image of the world at night. One thing you should keep in mind is that you are not necessarily looking at actual lights here but rather the thermal energy that is released from the planet at night. In some cases, you can say that the brighter the area, the more urbanized it is; however, that is not always true. Zoom in on the Middle East - what are the bright spots that you see in this region? If you look closely at Africa, you can see the outline of the Sahara desert...why does it appear brighter than the region to the south? Something else that is really neat, try adding the highway file from your ArcCanada data, zoom in on one province at a time and you can see how the thermal energy follows the street files...

There are a lot of interesting patterns that can be examined here but I will leave that up to your students!


K-12 Industry Manager

ESRI Canada: voice. 416-441-6035    fax .416-441-6838

Visit the ESRI Canada Web Site - http://www.esricanada.com/