aligning an image on top of another image

Did you possibly group the layers by hitting Cmd+G instead of Cmd+T (to transform)?

Make sure you have Layer 1 selected and use the Move tool to reposition it. If you need to resize and/or rotate the layer, press Cmd+T and resize handles will appear.  Hover outside the corner handles to rotate the layer. 

It would help if you post the aerial photo & the map so that we can provide hand-on advice. Absent that, here are some suggestions:

1. Make sure that the resolution of both the photo & map are the same value. The rule of thumb for work on the web is 72px/in and for printing in the 240-300 px/in range.

2. In addition to layer opacity determinant values, there is also the option to change the blending mode on layer1. "Normal" is default. In the drop-down click on the next option, and then you can cycle through the rest of the blending modes with the down-arrow key on the keyboard.

3. You might consider enhancing the trails on the map. Open a blank layer at the top of the stack of layers, and with a black, round or square brush,  trace over the trails to make them stand out. Again, you have the options of opacity & blending mode on this layer.