title: Better documentation for arcgisimage, basemap python
body: <p>I am using the arcgisimage API to have map layers to my scatterplot.</p>
  
  <p>However, the documentation for the API, found here <a href="http://basemaptutorial.readthedocs.org/en/latest/backgrounds.html" rel="nofollow">http://basemaptutorial.readthedocs.org/en/latest/backgrounds.html</a> is not that good, especially concerning sizing of the images:</p>
  
  <blockquote>
    <p>xpixels actually sets the zoom of the image. A bigger number will ask
    a bigger image, so the image will have more detail. So when the zoom
    is bigger, the xsize must be bigger to maintain the resolution</p>
    
    <p>dpi is the image resolution at the output device. Changing its value
    will change the number of pixels, but not the zoom level</p>
  </blockquote>
  
  <p>THe xsize mentioned is not defined anywhere, and doubling the DPI between 300 and 600 doesn't affect the size of the image. </p>
  
  <p>Anyone have a better documentation/tutorial?</p>