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Best way to display points depicting ocean current speed?

April 10 2008 | 0 comments
Categories: Symbology

I am working with ocean current speed point data in ArcGIS 9.2. I am trying to create a visual display that conveys the speed of current over time. My data is points and I have been using graduated colors where a pale color is a slow speed and a dark color is a faster speed. I've also changed the point sizes to make the faster speeds a smaller point, and the slower speeds a larger point. My speeds range from 0 knots to 6 knots and I would like to have half knot intervals. My problem is my points are so close together that its hard to really see some of the data. The data points were collected by using a GPS enabled drifter which collects position data about every eleven seconds.

My question is this: do you have any suggestions for how to symbolize this data or any examples of anyone that is already producing maps like this?

Mapping Center Answer:

If you have data that are hard to see in a congested area, you might consider the use of inset maps – these provide close up views of those areas that are difficult to se because of symbol and/or label overlap. Of course, you can also work a little more with the symbols to see if you can change the range of sizes to fit more appropriate in the congested areas, as well as across the rest of the map itself. You are working with quantitative point data, so the appropriate visual variables (that is, the graphical characteristics of the point symbols) that you should change include size and/or color lightness or brilliance, so you have made appropriate choices already (lighter to darker colors and smaller to larger point symbols). You can also combine these so that your smaller points are the lighter color and the larger points are the darker color. It might help us to see an example of your map, if you don’t mind adding an attachment to your question.

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