Examining Ocean Currents:  Static maps vs. interactive GIS-generated web maps

Blog Post created by jkerski-esristaff Employee on Oct 1, 2018

Examining Ocean Currents


Limitations of Static Maps.  One of the advantages to using Spatial Technology in education is that you and your students have the capabilities of interacting with mapped data.   Let’s say you are teaching about ocean currents at some point. 


Examine this ocean currents map from Wikipedia:  https://en.wikipedia.org/wiki/Ocean_current#/media/File:Corrientes-oceanicas.png.  It is fairly clear, not overly detailed; unfortunately Australia is off on the side, as often happens on world maps. 


Examine this ocean currents map from NOAA:  https://en.wikipedia.org/wiki/Ocean_current#/media/File:Ocean_surface_currents.jpg  Again, it is OK, Australia is now nearer the center but the arrows are shorter and a bit more difficult to interpret. 


Neither of these maps is a vast improvement over the one created by the US Army in 1943, here:  https://en.wikipedia.org/wiki/Ocean_current#/media/File:Ocean_currents_1943_(borderless)3.png; in fact, the US Army’s choice of symbology actually make it more useful in some ways than the more current maps. 


You also may use maps on the wall of your classroom or in a textbook.  These maps may be wonderful as well and be useful to you.


But all these maps have limitations:  You as the educator are “stuck” with the projection chosen, the symbology used, and the scale.  They are all snapshots in time and cannot be updated.  You cannot add additional information to it and you cannot interact with it.  Printed maps can tear or be spilled on.  Wall maps or printed maps might require a lot of space.   By contrast, you will examine a 3D scene of ocean currents.


Enter the world of maps from Spatial Technology.  The advent of web based Spatial Technology has enabled a variety of different map and imagery layers to be combined in what are called web mapping applications, including this one on ocean currentsElsewhere on www.arcgis.com, you can explore and build some web mapping applications, including story maps (http://storymaps.arcgis.com).  


A 3-D map of ocean currents.  Right now, let’s start with this 3D Globe of world ocean currents:


Pan the map to Australia.  Note the navigation tools to the left of the map and experiment with them.  On the right side, make all of the layers visible.  Your map should look similar to that below.


Ocean currents activity 1

Make the legend visible.  Based on this map, one question you could post to the students is:  Say you want to find a swim beach.  On which coast(s) of Australia are being fed by a warm current and therefore, on which coasts would you find warmer water (north, east, south, or west)? 


What is another question you could pose to the students based on this map?


Changing the map.  You can see that not only is the map rendered as a 3D globe, you can examine the topography (called bathymetry) of the ocean floor, turn layers on and off, change the basemap, change the sun position to today’s date and time, examine the difference in the Coriolis effect in the northern versus the southern hemispheres, and more.  You can measure distances and areas on land and in the water, and since you are working with a 3D globe, your measurements will be more accurate than measuring off of a 2D map.  (Not perfect, but more accurate.  See documentation on the Esri site about map projections, accuracy, and scale).  You can even share the map as a URL.  When you do, the person you send the link to will be able to open the map in the exact spot you desire and with the layers, basemap, and sun angle all set to the way you set it. 


Floating on the High Seas.  In addition, since Spatial Technology is now a platform, you and others can build on top of it.  Let’s use one educational and fun example.   Looking at the ocean currents, you may have been thinking, if I dropped a bottle, or set off on a raft, off of Australia, where would the bottle or my raft float to?  


Go to the Message in a Bottle web mapping application, below.  This is based on the same data you have been observing with one additional wonderful capability:


Again, pan and zoom to Australia or another area of interest to you.  Set the number of days to 250 and the buffer distance to 25 km.  Take the default of today’s date.  Hypothesize about the direction and distance a bottle or raft would float in 250 days off the north coast and off the east coast of Australia.  Then, click on the map to drop 1 point off the north coast of Australia, let the tool run, and observe the result.  Drop 1 additional point off the east coast of Australia, again letting the tool run and observing the result.  The results will look similar to that below:

Ocean currents activity 2


Are the results (direction and distance) consistent with your hypothesis?  Why or why not? 


Extend this activity.  This web mapping application could therefore serve as a useful tool that can teach that the ocean currents move in different directions, but they also move at different rates of speed.  And they also move differently depending on the time of year.  Change the time of year from today’s date to six months ago and observe any differences.  Why do the differences exist?