Part 3—EXPLORE Geographic Data
Step 1 – Prepare Your Data Table
- Compile your data into an electronic table. These instructions tell how to enter the data into a spreadsheet program such as Microsoft Excel and then import it into My World.
- Your completed table should look similar to the table on the right.
- Each column is referred to as a field and each row (except the first row, which contains field names) is a record.
- The field names should be eight letters or less and should contain no spaces or special characters.
- Text descriptions within each record must be very brief, and the column width should expose all of the text.
- Do not leave any cells within your table blank (use NA or -999 for empty records).
- Notice that in North America, latitude values are positive numbers (because we are north of the equator) and longitude values are negative (because we are west of the Prime Meridian)
- Highlight one column at a time, and from the Format menu, choose Cells...
- In the Number tab, select the appropriate Category for each column. Choose text for words or number for values.
- If the column contains numerical data, you must specify the number of Decimal Places. After making these selections, click OK.
- Choose File > Save As... and give your file an appropriate name, such as local_data.
- Browse to an appropriate folder for storing the file. This might be the desktop or a personal folder or directory.
- Access the pull-down menu at Save As Type or Format and select CSV (Comma delimited) to get a .csv extension.
Step 2 – Create a Local Map in My World
- Launch My World GIS by double-clicking its icon or choosing it from the Start menu.
- My World GIS opens in Construct Mode showing three main parts: Data Libraries on the left, a Layer List in the middle, and the Map on the right-hand side.
- To find your UTM zone, look in the Data Library column and locate the U.S. States file. Click and drag it into the Layer List column.
- Do the same for the Continental U.S. UTM zones (10-19) file.
- Click the Visualize tab in the upper left of the My World window and select the Pointer tool.
- Click the part of the map where you live, and check which zone is highlighted in the legend on the far right.
- Once you know your UTM zone, go to File > New Project. Click No when queried to save the current project.
- At the top of the Data Library column, use the pull-down menu to select Dynamic Web Images. You must have an active Internet connection in order to access these images.
- Locate the Aerial Photo and Topo Map for your UTM zone and drag them to your Layer List. To load the example project, choose UTM zone 11.
- Explore these maps briefly in the Visualize mode. Use the Zoom and Pan tools to check them out. It will take a moment for the images to load each time you zoom in.
Any time geographic coordinates from the surface of a sphere (Earth) are "projected" onto a flat, two-dimensional grid, it causes some distortion. For instance, if you try flattening an entire orange peel onto a piece of paper, you will see that you can't make the peel into a rectangle without some stretching or squeezing (distortion). Different map projections use different mathematical rules for how to stretch the round Earth onto a flat map. Thus, you can view two maps of the same part of Earth, but if they were produced in different projections, the features will not align.
The order in which you bring files into a My World project can be critical if the layers are in different map projections. My World generally converts added files into the projection of the original layer. Generally, you should load satellite or aerial photographs first, then add shape, line, and point layers. For more information on map projections, visit The Geographer's Craft
Step 3 – Import the Data
- Click the Construct tab so you are in construct mode.
- Choose File > Import New Layer from File.
- Browse to where you saved your local_data.csv file, select it, and click Open.
- Use the radio buttons to make sure that the appropriate columns are designated as latitude and longitude. Accept the other default options and click OK.
- Your data has now been converted into a map layer of points. At the top of the Data Library, use the pull-down menu to select All Data Files. Drag your local_data layer into the Layer List.
- Click the Visualize tab.
- To view your points, click local_data in the Layer List to make it active, then click on the Zoom to Active Layer tool above the Map window.
- Adjust the image by as needed by Zooming In and Out until all points are easily viewed.
- In case you wish to pan away from this exact view, in the Map window select Map View, select Save Current As... from the pull-down menu.
- Give this view a name.
- This function allows you to quickly zoom back to this exact area with one simple click.
- This function is especially useful when you are moving back and forth between multiple portions of the map.
Step 4 – Link Images to Your Map
- Open the folder of the images that you will link to the project. To work with the heat island example, download a zipped file (Zip Archive 297kB May6 08) containing digital photos of the example project. Photo names indicate the sample location that they show.
- In My World, click the Edit tab then double-click your local_data file to open its data table.
- Click the New Field... button and enter "Linked images" as the name. Change the Data Type to Link then click OK. A new column will appear in the data table.
- To add links to each location, double-click in the cell of the new column.
- In the Editing Link... dialog, give a descriptive name for the image, then browse to the folder where it is stored.
- When you click OK, the path to that image is stored, and users will be able to access it from your project.
- To link a web page to a specific point in your project, enter a Link URL in the Editing Link dialog.
- To link a saved file such as a .doc or .pdf, click Choose File, browse to the appropriate file then click Open, then click OK.
- Continue adding links for the pictures, files, or websites you want users to be able to access from your project. You will learn how to access these links in Part 4.