Week 12: Comparing Geospatial Tools
On this page
Download the Compressed File of GeoTIFF Images and Data about Ridley Turtles
Launch ArcGIS ArcMap and Add Data Layers
Add X/Y Data for Ridley Sea Turtles
Explore the Attribute Table of RidleyTurtle08
Analyze the Data by Querying and Symbolizing
- Perform a database query to find out where the turtles were by month
- Symbolize the turtle data by month
- Perform a database query to find out which turtles traveled where
- Symbolize the data by turtle name
- Measure the distance traveled by a single turtle
- Measure the distance from the shore to the farthest point from land that a turtle travels.
Learn More about the Threats Facing Olive Ridley Sea Turtles Today
Resources
Exploring Ocean Data with ArcGIS
Olive ridley sea turtles (Lepidochelys olivacea) are named for their olive colored shell or carapace. They look very similar to the closely-related Kemp's ridley sea turtle. Adult olive ridley turtles can weigh up to 110 pounds and are approximately 24 to 30 inches long. Hatchlings, or baby turtles, weigh only a few ounces. It is believed that olive ridleys have lifespans averaging around 50 years in the wild. While olive ridleys are the most abundant sea turtle species in the world, they are currently classified as endangered.
Like other sea turtles, they do not breed until 10 to 15 years of age. At that time, they return to the beaches of their own youth to lay their eggs. They lay hundreds of eggs in each nest. The peak nesting season for olive ridley turtles in the Eastern Pacific is during the months of September and October. These turtles have adapted a nesting strategy of safety in numbers. Typically, they arrive at their nesting sites in large groups. The turtles gather offshore and come ashore as a group to nest, an event called an arribada, which is Spanish for arrival. Often, hundreds of thousands of turtles will nest at the same location and time. While this provides some safety against predators, it also makes the turtles vulnerable to environmental disasters, such as oil spills and predation by humans. No other turtle has been observed nesting in such a synchronous manner as the olive ridley. After females lay their eggs, they return to the sea and continue to forage. Hatchlings migrate to the ocean around 60 days after the eggs are laid.
top of pageDownload the Compressed File of GeoTiff Images and Data about Ridley Turtles
- Right-click the link below to download the zipped file of data and images.
RidleyTurtlesAM.zip (Zip Archive 5.7MB May7 10) - Unzip the file. A folder called RidleyTurtlesAM will be created.
- Move the entire RidleyTurtlesAM folder into the Data folder inside the ArcGIS folder. (Path: c://eyesintheski2/week12/RidleyTurtlesAM)
Launch ArcGIS ArcMap and Add Data Layers
- Launch ArcMap by double-clicking its icon on your desktop or by clicking its icon in the Launch Bar.
- To add a September 2008 Sea Surface Temperature image, click the Add Data
button. Navigate to the RidleyTurtlesAM folder. Click once on Sept2008SeaSurf.TIF to select the image. Then click Add. - Repeat the procedure to add the Sept2008Chlorophyll.TIF image.
- Uncheck the Chlorophyll layer to turn it off and make sure that the 2008 Sea Surface Temperature layer added propertly. Then turn the Chlorophyll layer back on.
- Last, click the Add Data
button and navigate to the World folder. Click once on country06.shp to select it. Then click Add.
- Edit the properties of the cntries07.shp to display it with a light gray fill and a dark gray outline. The map now shows countries of the world layered onto the 2008 sea surface temperature and chlorophyll images.
- Table: c://eyesinthesky2/week12/RidleyTurtlesAM/RidleyTurtles08.csv
- X field: Longitude
- Y field: Latitude
- The Output Directory defaults to the current folder that you opened the Turtle file from. Accept this default.
- Click OK.
- Right click on the RidleyTurtles08.csv Events layer. Click on Data > Export Data.
- Navigate to project folder and give Ridley Turtle points a name and click Save.
- Click OK and click Yes to add exported data to your map as a layer.
- Draw features using: Single Symbol
- Style Circle1
- Color White
- Size 5
- Click OK and Click Apply
- The 2008 Ridley Turtles will now be displayed on the map as white dots.
- Right click once on RidleyTurtles08 layer and then click on Zoom to Layer. Make sure to turn off the Sept2008Clorophyll layer.
- Save your project file. top of page
- Open the Attribute Table of RidleyTurtles08 and inspect the fields in the table.
- Sort the table in ascending order by MONTH.
- During what months was the data collected? top of page
- Where were the turtles in September? Write and execute a query to find out.
- Where were the turtles in October? Write and execute a query to find out.
- Where were the turtles in November? Write and execute a query to find out.
- Where were the turtles in December? Write and execute a query to find out. top of page
- Which turtles traveled where each month? To find out, symbolize the turtle tracking data using a different color for each month.
- The 2008 olive ridley turtle data are now displayed so that each month of turtle paths is in a different color.
top of page
- Where did Gloria travel?
- Where did Buttercup travel?
- Which turtles traveled where? To find out, make a copy of the existing turtle layer to create a second turtle layer and symbolize each turtle's tracking data using a different color.
- The 2008 olive ridley turtle data are now displayed so that each turtle's path is in a different color.
- Carefully observe the turtle tracks. Did all the turtles travel the same path? Describe their routes. top of page
- How far, in total, did each of the turtles travel during the four months recorded on the map?
- Which of the turtles traveled the farthest distance away from shore?
- Click on the Measure tool
in the toolbar. From the drop-down menu choose miles as the unit for the measuring. Click, drag, click, drag, click, drag with the Measure tool as long as needed to use small segments to trace out the path of a turtle. The measure tool keeps a running total of the length of these segments. - Use the Measure tool to trace out the path of each turtle and find out how far each one traveled. top of page
- Click on the Measure tool
in the toolbar. From the drop-down menu choose miles as the unit for the measuring. Click and drag a line from the shore to the point farthest from land. The line should be perpendicular to the shore. Notice the measurement in the upper left corner of the map window. - What is the farthest distance that any of the turtles traveled in a straight line from the shore?
top of pageAdd Monthly Images of Sea Surface Temperature and Chlorophyll to Explore Patterns
Chlorophyll is a proxy data set for phytoplankton, which is at the base of the food web. Olive ridley turtles are pelagic, spending most of their lives swimming in nutrient rich waters where there is upwelling. They are opportunistic feeders and primarily consume shrimp, small fish, and jellyfish.
- Click the Add Data
button and navigate to the RidleyTurtlesAM folder. Add the three other months (October, November, December) of sea surface temperature and chlorophyll images to the project.
- Turn layers on and off to investigate the relationship between the turtles' travels and these images.
top of pageLearn More about the Threats Facing Olive Ridley Turtles Today
The historic olive ridley fishery in Mexico was, at one time, the largest turtle fishery in the world. Today, turtles are accidentally caught in shrimp trawls, longlines and gill nets. Once caught, they drown because they cannot resurface to breathe. Sea turtles also confuse trash, especially plastics, such as shopping bags and even balloons, for food and die due to starvation and choking.
Today, due to several factors, the olive ridley turtle is listed as endangered by the International Union for Conservation of Nature (IUCN). These factors include the harvesting and degradation of nesting sites. Once common in Mexico, only one nesting site remains. All over the world olive ridley turtles are at risk due to the harvesting of their eggs. Additionally, tens of thousands of olive ridleys, and other turtles, are accidentally caught in fishing nets, purse seines, and trawls. Conservation efforts are now being implemented for the olive ridley and other turtles. These efforts include turtle excluder devices (TEDs) on fishing gear. Around the world, conservation of turtles is an important topic and priority for fishers and other concerned citizens.
top of pageResources
- Whalenet - Source of the data in this activity
- Sea Turtle Tracking Projects at the Caribbean Conservation Corporation
- Sea Turtle Biographical Information
- NOAA Fisheries Olive Ridley Turtle Page
- US Fish and Wildlife Olive Ridley Turtle Page
- Argos Transmitters Protecting Biodiversity
- Tracking of Pacific Pelagics
- Click the Add Data
Show me how to add the data layers
Hide
top of page
Add X/Y Data for Ridley Sea Turtles
Add ridley turtle data from 2008
To map the 2008 Ridley Turtle tracks using Longitude and Latitude coordinates, choose Tools > Add XY Data. The Add XY window opens. Click the Browse
button to navigate to the file named RidleyTurtles08.csv. (Path: c://eyesinthesky2/week12/RidleyTurtlesAM/RidleyTurtles08.csv). Choose Longitude for the X Field and Latitude for the Y Field. Draw the XY points using symbols that are White Circles with a point size of 5. The options in the Add XY window are as follows:
Convert XY data to shapefile
To get full functionality from your XY points, it is necessary to convert your XY point layers to shapefiles. It is a simple two step process.
top of page
Symbolize by color
In the Properties window, click on the symbol button. In the Symbol Selector window, change the color of the turtles to Whitewith no outlines and size 5. Select the following options:
Note: If you enter the X and Y fields incorrectly, the data will either not project or will project incorrectly. Also, remember that when ArcGIS imports and projects a tabular dataset onto a map, it is NOT creating a shapefile. Those XY coordinates are just graphic dots and you must convert them to a shapefile to be able to perform different analytical operations on those dots. Once you convert the dots to a shapefile, the next time you want to see this dataset on your map as a layer, just click the Add Data button and look for the shapefile of the same name as the original table in the Ridley Turtles folder. For the 2008 Ridley Turtles data, you will find a file called RidleyTurtles08.shp, that has a .shp extension.
Explore the Attribute Table of RidleyTurtle08
Analyze the Data By Querying and Symbolizing
Perform a database query to find out where the turtles were by month
Symbolize the turtle data by month
Perform a database query to find out which turtles traveled where
Symbolize the data by turtle name
Five different olive ridley turtles, (Gloria, Showdancer, Carmen, Buttercup, and Esperanza) were tracked in 2008.
Measure the Distances that Sea Turtles Travel
Olive ridley turtles are omnivores; they eat algae, small fish, crabs, shrimp, rock lobsters, jellyfish, and tunicates. They are pelagic, which means they spend most of their lives swimming and foraging in deep water. Olive ridleys have been observed thousands of miles offshore. They can dive to depths of 500 feet to forage on benthic, or bottom dwelling invertebrates. However, these adaptable turtles can also be found swimming in water nearly 10,000 feet deep. Scientists who study how these animals move use satellite images showing sea surface temperature and chlorophyll concentration to look for indicators of their movement.
