All About Background Maps in JMP 9: NASA Server and Web Map Service
Nov 9, 2010 1:09 PM
Previously, I wrote about the image-based background maps that are provided as part of the JMP install. These maps work well when you are viewing a larger area of the world, such as a country or even a state or province.
But if you want to zoom in closer, these maps start to degrade. The resolution of the Simple Earth and Detailed Earth maps are not high enough to zoom in on a city, for example. To get that level of detail, we need to use another source -- the Internet. JMP 9 has two options on the background map dialog for Internet sources. Those options are NASA server and Web Map Service.
The NASA server provides maps for the entire Earth. Here is a graph of the Earth, which we’ve seen before, but this time it is using the NASA server as its source for the background map. It also has a boundary map turned on, to show the outlines of the countries.
Not only does this server cover the entire Earth, but you can also zoom in on a much smaller area of the Earth and still get a reasonable map. Here is a map showing the Colorado River running through the Grand Canyon, in Arizona. The Grand Canyon Village is visible in the bottom of the map.
If you look at the axes values, you can see that we are zoomed in such that we are viewing an area that is less than 1/10° by 1/10°. The Simple Earth and Detailed Earth background maps cannot display that kind of resolution. The NASA server can give us a fairly detailed view of any land mass on Earth. Water, however, is simply filled in as black. The NASA server is free to access, but it is also limited in availability. If the server is temporarily unavailable or becomes overloaded with requests, it will deliver an error message instead of the requested map.
Another Internet-based option for background maps is a Web Map Service (WMS). The WMS option allows you to specify any server that supports the WMS interface. The NASA server is an example of a WMS server, but we have provided the URL and a layer name for you. With the WMS option, you must know the URL to the WMS server and a layer name supported by the server. Most WMS servers support multiple layers. For example, one layer may show terrain, another layer may show roads, and still another layer may include water, such as rivers and lakes. By specifying the URL for the server and the layer, JMP can make a request to the server and then display the map that is returned.
Here is a popular map around my office. I used a WMS server that provides maps for Wake County, North Carolina. The server URL is http://columbo.nrlssc.navy.mil/ogcwms/servlet/WMSServlet/Wake_County_NC_Maps.wms and the layer is named 16:0. This map plots the location of Starbucks coffee shops around SAS headquarters in Cary, NC. Blue indicates a free-standing Starbucks. Red indicates it is inside another establishment, such as a grocery store or gas station.
There are 20 Starbucks shops within a three-mile radius of my office. It is no wonder that Cary is consistently rated as one of the top cities to live in, in the United States. Perhaps I should use JMP to analyze the traffic patterns between each Starbucks and the office each weekday morning -- and then see how that relates to productivity!
If you want to use the WMS option for a background map, the question then becomes: Which WMS server can I use? There are many WMS servers freely available across the Internet. Most of them provide maps only for a particular area of the world, and each of them supports their own layers. So each user will likely have to search out the appropriate WMS server for his or her particular situation. A good starting point is Google (or whatever your favorite search engine is). Also, here are some links that I have found useful for finding a WMS server:
Once you find a WMS server, you still have to figure out what layers it supports. This can be a little tricky. But never fear -- I wrote a JMP add-in to help you with that. But that is a topic for my next blog post.
Until then, see if you can find a good WMS server for your particular needs. And, as always, feel free to let me know what you think.