We've all seen rainbows. It's the reflection of sunlight broken into its various color components. We see them in the sky and in the spray of a water hose or waterfall.
We've seen our reflection in the mirror as we comb our hair. We can see specks of dust on the polished surface of furniture. Even the heat rising from the earth's surface will create a mirage that may show an image of somthing beyond the horizon.
All of these images require the observer to be looking at the correct angle of reflection, or the observer will not see it.
At the given coordinates you will find two plastic window panes. At the correct angle of reflection, you will discover the seven digits of the N and W coordinates for the final cache.
GOOD LUCK