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1. In the Catalog pane, expand the Databases section and the HydrologyLab.gdb geodatabase.
2. Drag the Watersheds feature class into the Lab2 map view.
3. In the Contents pane, double-click the Watersheds layer.
4. In the ‘Layer Properties’ window, click the Source tab.
5. Scroll down and expand the Spatial Reference section.
   
   Notice that the layer is in a geographic coordinate system called NAD 1983, which stands for North American Datum 1983. Because the data has a geographic coordinate system, the coordinates are stored in degrees, which indicate the three-dimensional location of the data on Earth's ellipsoidspheroid. Though the data itself is stored in a geographic coordinate system, your computer monitor is flat, so, even though no projection has been defined, the data must be displayed in a particular projection. Whenever ArcGIS displays data in a geographic coordinate system, it uses a pseudo plate carrée projection, where one degree of latitude by one degree of longitude is represented as a square, rather than a curved trapezoid. In other words, all lines of latitude and longitude are evenly spaced. This type of projection results in stretching in the east-west direction, which increases the farther north or south from the equator you are mapping.
   
   
6. Close the ‘Layer Properties’ window.
   
   Working with geographic coordinate systems is fine for creating purely visual maps, as you did in Lab 1 (though the visual distortion can be disorienting and misleading), but, in this lab, you will be calculating areas, distances, and overlaps between features. Such calculations require the three-dimensional coordinates to be projected down onto a two-dimensional plane, so that the coordinates are stored in linear units, such as feet or meters, rather than degrees. In order to facilitate measurements of distance and area, you will now project the Watersheds layer into the State Plane Texas South Central projection which is best suited to mapping the greater Houston region.
   
   
7. In the Analysis tab, click the Tools button to open the Geoprocessing pane.
8. In the 'Find Tools' search box, type "Project".
9. Click the Project (Data Management Tools) Under Toolboxes, double-click the Data Management Tools toolbox → Projections and Transformations toolset → Project tool.
10. For ‘Input Dataset or Feature Class’, use the drop-down menu to select the Watersheds layer.
    
11. For ‘Output Dataset or Feature Class’, rename “Watersheds_Project” to “Watersheds_StatePlane”, since that is the name of the projection you will be using.
12. Next to the ‘Output Coordinate System’ box, click the Set Coordinate System button.
13. Double-click Projected Coordinate Systems → State Plane → NAD 1983 (2011) (US Feet).
14. Select NAD 1983 StatePlane Texas S Central FIPS 4204 (US Feet) and click OK.
    
    Because both the input and output coordinate systems are based on the NAD 1983 geographic coordinate system, no geographic transformation is required.
    
    
15. Ensure your ‘Project’ window appears as shown below and click Run.
    
16. Close Geoprocessing Pane.
    
    Now that you have the correctly projected layer, you no longer need the original NAD 1983 layer.
    
    
17. Right-click the Watersheds layer and select Remove.
18. Double-click the new Watersheds_StatePlane layer.
    
    Notice that the layer is now in a projected coordinate system, NAD_1983_StatePlane_Texas_South_Central_FIPS_4204_Feet.
    
    
19. Close the ‘Layer Properties’ window.
    

    You may have noticed that the visual appearance of the watersheds did not change in your Map Display, even though you projected them. That is because the data frame takes on the projection of the first layer added to it. Since you first added the original unprojected Watersheds layer into the data frame, which was in NAD 1983, the data frame displays the data in NAD 1983 (or Plate_Carrée). Currently, the projected Watersheds_StatePlane layer is being projected-on-the-fly back into NAD 1983 for visual purposes, so that the two layers are properly aligned in space.

    Move the cursor around the screen and notice that the coordinates in the bottom right corner of the Map Display are shown in decimal degrees. This is another clue that the data frame is still using a geographic coordinate system; however, you would like the data frame to display data using the local Houston projection.
    
    

20. At the top of the Contents pane, right-click the Lab 2 map title and click Properties.

21. Click the Coordinate System tab.
    
    While you could search for or navigate to the State Plane Texas South Central coordinate system, as you did before, in this case, you know that the same coordinate system is already used by the Watersheds_StatePlane layer. In such an instance, it is often easier to import the coordinate system from another known layer, especially if you are not familiar with the hierarchy of the coordinate system folders
    
    

22. On the ‘Coordinate System’ tab toolbar, click the Add Coordinate System button and select Import….
    

23. Double-click the HyrdologyLab geodatabase.
24. Select the Watersheds_StatePlane feature class and click Add.
    
    Notice that the familiar State Plane Texas South Central projection is now listed.
    
    
25. Click OK.
    
    Notice that the watershed boundaries are now more compact in the east-west direction, as expected, because the local projection results in less distortion than the Plate Carrée projection used to represent geographic coordinate systems.
    
    

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