Web-based Exercise #3:

Map Projection and Direction Finding

Special thank to Mr. Henry George Bottomley (http://www.btinternet.com/~se16/hgb/) . The following Java applet tools were created by Henry Bottomley. We thank Mr. Bottomley to grant the permission to use these Java tools in our lab exercises.


 

 

Estimated time: 4 hours

Grading:  8 points total (ONE point for each question).

 

Due Day: Mar 13 at the beginning of lecture (11:00am). You should upload your lab answers to the Blackboard ( http://blackboard.sdsu.edu  )  before the lecture and submit a paper print-out version in the class.  We will use the Timestamp on your documents in the Blackboard to check if your assignment is late or not.

(In your upload file, please use this title: [GEOG104-LAB-#-[Your name].doc (or txt or pdf).  Please write down your answers in MS Word or WordPAD or other word processing software.  Please always save a local backup copy of your own answers.)

 

If you don't have Internet access, you can use our SAL lab (Storm Hall 338, third floor) on every Friday morning from 11:00am to 12:00pm.

 

 

1. Map Projection Demo Overview

 

Please spend 5 minutes to read this class Lecture Note Unit-3 -- map projection part: (Click here)

Also, please spend another 5 minutes to read the following introduction about map projection:

http://en.wikipedia.org/wiki/Map_projection

After the readings, please answer the following question:

 

Q1)  Why do we need map projections ? (Suggestion: use four or five sentences to answer this question.)

__________________________________

 

2.  On-line Map Projection Tool Exercise

Click the link http://www.btinternet.com/~se16/js/mapproj.htm.  (Open a new Window for displaying the on-line Java Map Projection tool.)

 

There are different demos for the map projections. We can try the default one first (Figure 1).

           Figure 1:  A Map Projection Demo

 

If you can not see the Java Applet running in your web browser, you have to:

You can adjust the size of the map by draging your mouse cursor on the lower-right corner of the World map.

Please read the text introduction below the applet (5 minutes), especially in the section of Lines on the image, and Scaling.

 

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)

 

Q2) Please answer these questions about the Mercator Projection:  What type of projection is it ? (Cylindrical? Conic? or Plane?) What is a "conformal" projection?  The Mercator projection is a conformal projection?

_______________________________________________

 

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

 

Q3)  Please answer the questions about the Mollweide Projection.   What are the differences of the circles (Tissot's Indicatrix) 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)? (Hint: refer to http://en.wikipedia.org/wiki/Mollweide_projection)

 

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

          Figure 6: Azimuthal Distance Projection

 

 

Q4) 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 Web Page

The main web page of the Decision Support System for Map Projections is composed of four drop down boxes ("Select Type of Area to Map", "Select What to Preserve", "Select Type of Data", Select Type of Raster Data") (Figure 7). You can also check a tutorial by clicking on "DSS Tutorial". Among the four drop down boxes, only the first drop down box should be active. The other drop down boxes will become active after you choose one of options on the first drop down box.

                                  Figure 7. Startup Screen

 

Click on the first drop down box (Select Type of Area to Map) (Figure 8).

 Type Down Selection Menu

                  Figure 8. Drop Down Select Box

 

There are three options on the first drop down box, such as "Global", "Continental", and "Regional". Select one of them. If "Global" is selected, the second drop down box(Select What to Preserve) will become active; if "Continental" is selected, the web page will move to "Continental" web page; and if "Regional" is selected, the web page will also move to the "Regional" web page.

To check the second option of the main web page, select "Global" on the first drop down box. Then, the second drop down box will become active. The options of the second box are "Area", "Shape", and "Compromise" (Figure 9). Select one of them.

Preservation Down Selection Menu

             Figure 9. Preservation Drop Down Select Box

 

Once one of the options on the second drop down box is selected, the third drop down box (Select Type of Data) will become active. The third drop down box has two options including Raster and Vector (Figure 10).

Data Down Selection Menu

                    Figure 10. Data Down Selection Menu

 

If you select "Raster" on the third drop down box, the fourth drop down box will become active. However, if you select "Vector", the "Submit" button will become active. 

Now, select "Raster" option on the third drop down box. There are two options on the fourth drop down box, including "Continuous" and "Thematic" (Figure 11). Once one of them is selected, the "Submit" button will become active.

 

Raster Data Type Down Selection Menu

                    Figure 11. Raster Data Type Down Selection Menu

 

When the "Submit" button becomes active,  make sure the parameters are correct. Then, click on the "Submit" button. A new window will show up and present the suggested projection based on your choices.

 

3. 2 The Continental Page

If "Continental" was selected from the first drop down box ("Select Type of Area to Map") on the main web page, the web page will move to the "Continental" web page. Read carefully the instructions on the top of the web page. The instructions are:

1) Make Preservation and Data Type selections in the appropriate boxes

2) Click the Continent you are interested in

Also, you can change options of three drop down boxes on the bottom of the web page.("Preserve", "Data Type", and "Raster Data Type")(Figure 12).

 

Continental Selector Page

                                                                    Figure 12. Continental Selector Web Page

The default options selected on the three drop down boxes (Figure 12) are "Shape", "Raster", and "Continuous". You can change the options by selecting other options. In the case that you select "Vector" on the Data Type drop down box, Raster Data Type drop down box will become inactive.

Once you decide options on the three drop down boxes, click on one of the continents on the map. Then, the suggested projection will be shown under the map. Click on other continents and check what kinds of projections are suggested (In Figure 13, Transverse Mercator is suggested for the options with "Shape", "Raster" and "Continous").

 

Projection Name Clickable

                                                       Figure 13. Projection Name Clickable

Click the suggested projection name (In Figure 13, click on "Transverse Mercator"). Then, the map of the suggested projection will show up. If you click on the map projection name under the map again, a new window for more details about the map projection will show up (Figure 14).

 

 

Figure 14. Detail Information about Transverse Mercator Projection

 

 

3. 3 The Regional Page

Now, go back to the main web page (http://mcmcweb.er.usgs.gov/DSS), and select "Regional" on the first drop down box (Select Type of Area to Map). Then, the window will move to the "Regional" web page. Read carefully the instructions on the top of the window.

1) Move and resize box around the region you are interested in

2) Make Preservation and Data Type selections in the appropriate boxes.

You can select options on the drop down boxes ("Preserve", "Data Type", and "Raster Data Type") on the bottom of the web page (Figure 15).

 

Regional Selector Page

                              Figure 15. Regional Selector Web Page

The default options are "Shape" "Raster", and "Continuous". You can modify the options like the case when you select options on the "Continental" web page.

When decisions for three drop down boxes are made, move and resize the blue box on the map. Then the projection for the region will be suggested. Like the case of Continental, click on the projection name suggested under the map. Then, the map with the suggested projection will show up.

 

 

3.4 Tutorial

The tutorial web page will show up when you click on the globe image that is labeled “DSS Tutorial” on the main web page. Once the globe image is selected, the window will be split showing the DSS on the top and the tutorial on the bottom. Initially, there should be four circles including DSS Applet, Global, Continental, and Regional. The DSS Applet circle should be green with red outline, whereas the other circles (Global, Continental, and Regional) are sky blue (figure 16). Only the most recent choice should be green; the rest should be sky blue. The red circle will show the path that has been selected.

 

Opening Page with Tutorial

                      Figure 16. Opening Page with Tutorial

 

If you select the options in the four drop down boxes as you did in the main web page, the graph will be changed and show additional circles like Figure 17.

 

 Tutorial Graph

                       Figure 17. Tutorial Graph

 

If you place your mouse cursor on one of the circles, a message box will show up to explain the circles. In each message box, you will be able to obtain more detailed information by clicking on "more>>>".

Tutorial Graph with More Information Popup

                                                                                  Figure 17. Tutorial Graph with More Information Popup

 

Q5) Go to the main web page (http://mcmcweb.er.usgs.gov/DSS/). Select "Global", "Area", "Raster" and "Continuous" for each drop down box. List the suggested projection names and their latitudes. What are the characteristics of the projections? (Hint: click on the projection names) 

 

Q6) Go to the main web page (http://mcmcweb.er.usgs.gov/DSS/). If you select "Global", "Area", "Raster", and "Continuous" for each drop down box, "Behrmann Cylindrical Equal Area" will be suggested for 30 degrees which San Diego falls under. In addition if you select "Area", "Raster", and "Continous" on the "Regional" web page. Then, "Albers Equal Area Conic" projection will be suggested for San Diego region. What are the similarities and differences between Behrmann Cylindrical Equal Area and Albers Equal Area Conic? (Refer to http://mcmcweb.er.usgs.gov/DSS/ImgHTML/Behrmann30deg.html and http://mcmcweb.er.usgs.gov/DSS/ImgHTML/Albers.html)

 

Find the Direction (using a Compass) and the shortest distance.

Please spend 20 minutes to read the following web pages.

How to read a Compass?
http://www.funsocialstudies.learninghaven.com/articles/compass.htm

Finding the directions without a compass.
http://www.learn-orienteering.org/old/nocompass1.html

 

Questions:

Q7)  Bearing question. A compass bearing of 165 degrees APPROXIMATELY describes

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

 

Q8) 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

Due Day: Mar 13 at the beginning of lecture (11:00am).

Note:

You should upload your lab answers to the Blackboard ( http://blackboard.sdsu.edu  )  before the lecture and submit a paper print-out version in the class.  We will use the Timestamp on your documents in the Blackboard to check if your assignment is late or not.

(In your upload file, please use this title: [GEOG104-LAB-#-[Your name].doc (or txt or pdf).  Please write down your answers in MS Word or WordPAD or other word processing software.  Please always save a local backup copy of your own answers.)

 

 

Q1)  Why do we need map projections ? (Suggestion: use four or five sentences to answer this question.)

Q2) Please answer these questions about the Mercator Projection:  What type of projection is it ? (Cylindrical? Conic? or Plane?) What is a "conformal" projection?  The Mercator projection is a conformal projection?

Q3)  Please answer the questions about the Mollweide Projection.   What are the differences of the circles (Tissot's Indicatrix) 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)? (Hint: refer to http://en.wikipedia.org/wiki/Mollweide_projection)

Q4) 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?

Q5) Go to the main web page (http://mcmcweb.er.usgs.gov/DSS/). Select "Global", "Area", "Raster" and "Continuous" for each drop down box. List the suggested projection names and their latitudes. What are the characteristics of the projections? (Hint: click on the projection names) 

Q6) Go to the main web page (http://mcmcweb.er.usgs.gov/DSS/). If you select "Global", "Area", "Raster", and "Continuous" for each drop down box, "Behrmann Cylindrical Equal Area" will be suggested for 30 degrees which San Diego falls under. In aiddtion if you select "Area", "Raster", and "Continous" on the "Regional" web page. Then, "Albers Equal Area Conic" projection will be suggested for San Diego region. What are the similarities and differences between Behrmann Cylindrical Equal Area and Albers Equal Area Conic? (Refer to http://mcmcweb.er.usgs.gov/DSS/ImgHTML/Behrmann30deg.html and http://mcmcweb.er.usgs.gov/DSS/ImgHTML/Albers.html)

Q7)  Bearing question. A compass bearing of 165 degrees APPROXIMATELY describes

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

Q8) 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 )

 

 

If you don't have Internet access, you can use our SAL lab (Storm Hall 338, third floor) on every Friday morning from 11:00am to 12:00pm.