Additional/unnecessary map image download?

Discussion created by sdurkin on May 5, 2014
I have a simple application that displays a map in a box and has a few buttons to toggle between the different sets of imagery that are available.  When the page first loads, the default behavior is simply to show the map for the set of imagery that has been designated as the default.  However, I've noticed (via the Chrome console's Network tab) that there is an additional map image being downloaded beforehand.  This image is of the entire state of Kansas (useless to my application).  It doesn't happen on subsequent requests for maps from the other available sets of imagery.

I'm trying to optimize the application for users with slow connections, and in doing so I noticed this seemingly unnecessary processing which I would like to avoid if possible (I also noticed that it doesn't *always* happen ... I tried using each of the other sets of imagery as the default, and sometimes it didn't happen, but I was unable to reproduce the behavior consistency).  Is this normal behavior?  Or is there more likely a problem with my implementation?

Thanks for any help.