WETMAAP Technique 2
Cocodrie Element 6 

Technique 2:  Manual GIS
Element 6:  Channel Overlays 

Materials:

            1957/1964/1980 1:24,000 scale Lake Quitman-Cocodrie Topographic Quadrangle

            1994 1:24,000 scale  Lake Quitman-Cocodrie Topographic Quadrangle

            (3) 11"x 17" clear film overlay

            drafting tape

            Colored marker pens: Orange, Green. Purple 

Exercise:  

            1. Use 1:24,000 scale 1957/1964/1980 Lake Quitman-Cocodrie Topographic Quadrangle

            2. Use a clear film 11”x 17”overlay.

            3. Tape the clear film overlay on top of the 1:24,000 scale map. Tape at the top edge.

            4. Use the Green pen.

            5. Use the Green pen to make four “corner marks” (tick mark 2) on the overlay, one at each corner of the study site.

            6. Trace the shorelines of Bayou Petite Caillou in Green on the overlay.

            7. At the bottom of the overlay (in green) draw a short horizontal line and label beside it “1980 Bayou Petite Caillou”. 
   
            Hint: Use of a symbol with a short description beside it is a “key,” or means of identifying selected features. 

            8. Remove the “1980 Bayou Petite Caillou” overlay.

            9. Use a second 11"x 17”clear film overlay.

            10. Tape the clear film overlay on top of 1:24,000 scale map. Tape at top edge.

            11. Use the Purple pen.

            12. Use the Purple pen to make four “corner marks” (tick mark) on the overlay, one at each corner of the study site.

            13. Trace the shoreline of the primary and secondary roads in Purple on the overlay. 

           14. At the bottom (in purple) draw a short horizontal line the same length as the green line and label it “Roads.” 

            15. Remove the “Roads” overlay.

            16. Use the third 11" x 17” clear film overlay.

            17. Tape the clear film overlay on top of the 1:24,000 scale map. Tape the top edge.

            18. Use the Orange pen.  

            19. Use the Orange pen to make four “corner marks” (tick mark 2) on the overlay, one at each corner of the study site. 

            20. Trace the shoreline of the Houma Navigation Channel in Orange on the overlay

            21. At the bottom (in orange) make a dashed line and label it “1980 Houma Navigation Channel.” Do not remove this overlay. 

            Hint:  Combining several single “key” items creates a “legend.” Every map should have a legend 

            22. Tape the “1980 Bayou Petite Caillou” and “Roads” overlays one on top of each other, over the “1980 Houma Navigation Channel” overlay. Use the four corner marks to line-up (“register”) the overlays on top of each other. 

             Hint:  Tape one overlay at the bottom edge and the other overlay at the left or right edge. By attaching the overlays at opposite edges, you can flip the overlays up and down in various alignments. You have created a manual GIS.