In the left drop down box, select “Mercator”, then the map will be re-projected as Mercator projection (Figure 2).

                     Figure 2: Mercator Projection

You can change the “Centre” of the map by selecting a mode in the “Centre” drop down menu or specifying the Longitude/Latitude and direction of the center (Figure 3). (Please try different Center of the Mercator project:   North pole / South pole / Pacific / Random. )

            Figure 3: Changing the Center to South Pole

Read the brief introduction for the Mercator projection at http://en.wikipedia.org/wiki/Mercator_projection.  ( 5 minutes)

A2: Please answer these questions about the Mercator Projection:  What type of projections is it ? (Cylindrical? Conic? or Plane?)      What is a "conformal" projection? Does the Mercator projection is a conformal projection?

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Now we need to visualize the map distortion for each different map project methods. .  In cartography, we can use a special technique called, Tissot’s indicatrix.   The Tissot’s indicatrix is using perfect circles patching on the Earth Globe surface, then with different map projections, the shape and size of the circles will be changed according to the different projection methods.   These changes indicate the distortion of each map projection on the different locations of the Earth Surface. 

•       Now go to http://www.btinternet.com/%7Ese16/js/tissot.htm. Still, choose Mercator projection and a group of circles will be drawn on the map (Figure 4).

•      Read the brief introduction for the Tissot's indicatrix at http://en.wikipedia.org/wiki/Tissot%27s_Indicatrix.

               Figure 4: Tissot’s Indicatrix of Mercator Projection

What did you see on the new maps? How can you tell from the indicatrix?  Do the indicatrix indicate equal area or conformal projection?

•       Now try the "Mollweide" projection (Figure 5).  Try to use different centres and see the changes of the Mollweide projection with the Tissot's indicatrix.

         Figure 5: Mollweide Projection with Tissot’s Indicatrix

A3.  Please answer the questions about the Mollweide Projection.   What are the differences of the circles between the Mercator projection and the Mollweide projection?  What type of projection is the "Mollweide" projection?  ((Cylindrical? Conic? or Plane? or Pseudo-cylindrical )   What are the characteristics of the Mollweide projection (conformal, equal-area or equidistant)? 

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(Suggestion:  Visit http://en.wikipedia.org/wiki/Mollweide_projection to get the answers).

•       Now try the "Azimuthal Distance" projection (Figure 6).

          Figure 6: Azimuthal Distance Projection

A4, Please use the tool http://www.btinternet.ckom/~se16/js/mapproj.htm to compare the longitude and latitude lines (or called gratitude) for the three different projections:  Mercator projection, Mollweide projection, and the Azimuthal projection.  (which projection has straight lines? Which one has the most curved lines?).

3.  Decision Support System for Map Projections of Small Scale Data, Version 2.0

•       Click the link http://mcmcweb.er.usgs.gov/DSS/ (Open a new Window.)

3. 1 The Main Page

When the Decision Support System is opened, a page with the USGS logo, four down selection combo boxes, a submit button, a button to show the tutorial, two links to other pages(one to the Java site to download the Java runtime environment, and the other to the main USGS Cartographic Research web page), and the USGS standard footer is seen(figure 7).

                                  Figure 7. Startup Screen

Of the four combo boxes and submit button, the first combo box(Select Type of Area to Map) should be the only one that is active, the others(Select What to Preserve, Select Type of Data, Select Type of Raster Data, and Submit button) should be inactive.

To make the first selection, click on any area of the "Select Type of Area to Map" combo box(figure 8).

                  Figure 8. Type Down Selection Menu

The choices of "Global", "Continental", and "Regional" are displayed. Choose one by clicking on it. If "Global" is chosen, the next combo box(Select What to Preserve) becomes editable; if "Continental" is chosen, the "Continental" page is displayed; and if "Regional" is chosen, the "Regional" page is displayed.

If "Global" is chosen, the "Select What to Preserve" combo box becomes editable; click on any area of that box to see the options. The selections now offered are "Area", "Shape", and "Compromise"(figure 9). Choose on of the options by clicking on it.

             Figure 9. Preservation Down Selection Menu

When an option has been selected on the "Select What to Preserve" combo box, the next combo box, "Select Type of Data", will become editable. Click anywhere on that combo box to see the "Raster" and "Vector" options(figure 10).

                    Figure 10. Data Down Selection Menu

If "Raster" is chosen, the next combo box, "Select Type of Raster Data", becomes editable, but if "Vector" is chosen, the "Submit" button becomes active.

If "Raster" data is chosen, the "Select Type of Raster Data" combo box becomes active. Click anywhere on that combo box to display the "Continuous" and "Thematic" options(figure 11). Once this is chosen, the "Submit" button becomes active.

                    Figure 11. Raster Data Type Down Selection Menu

When the "Submit" button becomes active, the user should check to make sure the parameters are correct. When the decisions have been verified, click on the "Submit" button. A new window will become active and display the suggested projection type based on the choices.

3. 2 The Continental Page

If "Continental" was selected from the "Select Type of Area to Map" combo box on the opening page(DSSApplet.html), the "Continental page" will start up in the same window. It should prompt the user to make"Preservation and Data Type" selection in the appropriate boxes, and to click on the Continent of interest. It also should be displaying a map and three selection boxes beneath it(Preserve, Data Type, and Raster Data Type)(Figure 12).

                                                                    Figure 12. Continental Selector Page

The decision in each box should be set by default to "Shape", "Raster", and "Continuous". Default settings can be changed by clicking on alternative selections. If "Vector" over "Raster" was chosen in the "Data Type" box, the "Raster Data Type" label and options(Continuous and Thematic) should become inactive.

Once the selections have been made, position your cursor over the continent of interest. The suggested projection is shown in real-time on the page. When the continent of interest has been selected, the suggested projection that is displayed will turn blue and become underlined(figure 13).

                                                       Figure 13. Projection Name Clickable

Once the suggested projection has turned blue the cursor can be positioned over the projection name and clicked on. In response, a new window will activate and show the suggested projection. If there is more than one suggested projection, it will show the image of the first suggested projection and provide links for all the projections where more information will be displayed about that particular projection. Otherwise, it will display the projection and additional information on the projection type that was chosen.

3. 3 The Regional Page

If “Regional” was selected from the “Select Type of Area to Map” combo box on the opening page (DSSAppletwbutton.html), the “Regional” page will start up in the same window. It should prompt the user to move and resize the box around the region of interest, and make “Preservation” and “Data Type” selections in the appropriate boxes. It also should be displaying a map and three selection boxes beneath it (Preserve, Data Type, and Raster Data Type) (figure 14).

                              Figure 14. Regional Selector Page

The decisions in each box should be set by default to “Shape”, “Raster”, and “Continuous”. Default settings can be changed by clicking on alternative selections. If “Vector” is chosen over “Raster” in the “Data Type” box, the “Raster Data Type” label and choices (Continuous and Thematic) should become inactive.

Once the selections have been made, position and resize the box around the region of interest. The projection suggested is shown in real-time and should automatically be blue and underlined, allowing the suggested projection name to be chosen. When the suggested projection is chosen, a new window will activate showing more details about that particular projection.

A5.  If "Global", "Area", "Raster", and "Continuous" are chosen, what kinds of projects are suggested for different latitudes? What are the characteristics of this projection?   If "Shape", "Raster", and "Continuous" are chosen in the regional page, which projection is suggested for the U.S.A.? What are the characteristics of this projection?

3.4 The Tutorial

The tutorial will activate only when you click on the globe image that is labeled “DSS Tutorial” on the opening page. Once that globe image has been selected, the window will split showing the DSS on the top and the tutorial on the bottom. Initially, there should be four nodes showing; DSS Applet, Global, Continental, and Regional. The DSS Applet node should be green and circled in red, whereas the other nodes (Global, Continental, and Regional) are light blue (figure 15). Only the most recent choice should be green; the rest should be light blue. The red outline will show the path that has been chosen.

                      Figure 15. Opening Page with Tutorial

Decisions can be made the same as described above in The Main Page, The Continental Page, and The Regional Page descriptions. When a decision has been made, it should be reflected in the graph shown in the tutorial (figure 16).

                       Figure 16. Tutorial Graph

At any time, the cursor can be placed over a green node in the tutorial. A message bubble will display a small explanation of why that element is used (figure 17). In each message box more information about projections is available by clicking “more”. A new window will activate and take the user to a website with more information.

                                                                                  Figure 17. Tutorial Graph with More Information Popup

Questions:

A. northerly direction;
B. northwesterly direction;
C. southeasterly direction;
D. southwesterly direction;
E. northeasterly direction

A8. What is “Great Circle” and “Small Circle” in Cartography? (See textbook pp115-117) or the following web link: http://en.wikipedia.org/wiki/Great_circle ,  http://en.wikipedia.org/wiki/Small_circle )

 

Please Answer the Following Questions

A1.  Why we need map projections ? (Suggestion: use four or five sentences to answer this question.)

A2: Please answer these questions about the Mercator Projection:  What type of projections is it ? (Cylindrical? Conic? or Plane?)      What is a "conformal" projection? Does the Mercator projection is a conformal projection?

A3.  Please answer the questions about the Mollweide Projection.   What are the differences of the circles between the Mercator projection and the Mollweide projection?  What type of projection is the "Mollweide" projection?  ((Cylindrical? Conic? or Plane? or Pseudo-cylindrical )   What are the characteristics of the Mollweide projection (conformal, equal-area or equidistant)? 

A4, Please use the tool http://www.btinternet.com/~se16/js/mapproj.htm to compare the longitude and latitude lines (or called gratitude) for the three different projections:  Mercator projection, Mollweide projection, and the Azimuthal projection.  (which projection has straight lines? Which one has the most curved lines?).

A5. Please use the tool http://mcmcweb.er.usgs.gov/DSS/. If "Global", "Area", "Raster", and "Continuous" are chosen, what kinds of projects are suggested for different latitudes? What are the characteristics of this projection?  Please use the tool http://mcmcweb.er.usgs.gov/DSS/DSSRegional.html.  If "Shape", "Raster", and "Continuous" are chosen in the regional page, which projection is suggested for the U.S.A.? What are the characteristics of this projection?

A6. If "Global", "Area", "Raster", and "Continuous" are chosen, Behrmann Cylindrical Equal Area is suggested for 30 degrees (e.g. San Diego). Also, If "Area", "Raster", and "Continuous" are chosen in the regional page, Albers Equal Area Conic is suggested for San Diego area. What is the difference between Behrmann Cylindrical Equal Area and Albers Equal Area Conic? (Reference : http://mcmcweb.er.usgs.gov/DSS/ImgHTML/Behrmann30deg.html  and http://mcmcweb.er.usgs.gov/DSS/ImgHTML/Albers.html)

A7.  Bearing question. A compass bearing of 165 degrees describes

A. northerly direction;
B. northwesterly direction;
C. southeasterly direction;
D. southwesterly direction;
E. northeasterly direction

A8. What is  “Great Circle” and “Small Circle” in Cartography? (See textbook pp115-117) or the following web link: (Reference: http://en.wikipedia.org/wiki/Great_circle , http://en.wikipedia.org/wiki/Small_circle)

Note: