WhirlyGlobe Tutorial draft - NASA GIBS Layers

NASA GIBS -
NASA provides a wealth of image layers for free. ''Steve adds the intro''.  These layers are available through their GIBS (Global Imagery Browse Services) website

You'll need to have done the [Remote Image Layer] tutorial.  Open your HelloEarth project and get ready.

If you haven't got one here is a suitable ViewController.m file to start with.  This version has a remote image layer already configured and it makes a nice starting point.

Let's start by explaining whatever????

### NASA GIBS base layer tile sources

All we need to do is replace the existing MaplyRemoteTileSource URL with one supplied thru the GIBS website.  Here are two URLs that provide a base layer for your Whirly Globe.


http://map1.vis.earthdata.nasa.gov/wmts-webmerc/MODIS_Terra_CorrectedReflectance_TrueColor/default/2015-06-07/GoogleMapsCompatible_Level9/

http://map1.vis.earthdata.nasa.gov/wmts-webmerc/VIIRS_CityLights_2012/default/2015-07-01/GoogleMapsCompatible_Level8/


Open ViewController.m. Now let's find where to add the image layer URL.  Scroll down thru viewDidLoad until you find the following code

// MapQuest Open Aerial Tiles, Courtesy Of Mapquest
// Portions Courtesy NASA/JPL­Caltech and U.S. Depart. of Agriculture, Farm Service Agency
MaplyRemoteTileSource *tileSource =
[[MaplyRemoteTileSource alloc]
    initWithBaseURL:@"http://otile1.mqcdn.com/tiles/1.0.0/sat/"
    ext:@"png" minZoom:0 maxZoom:maxZoom];


Replace the initWithBaseURL property with one of the selections above.
Also change ext with "jpg"
And match the maxZoom with the level of the GoogleMapCompatible Level (8 or9)

Run the project, and you should get a stunning NASA earth globe or map