This map shows you the line of sight between your site and the distant TV transmitter in the horizontal plane. If you know the area you may get a feel of why you have any line of sight issues you may have. Alternatively switch to satellite or hybrid view to see what is on the ground. It is also nice to confirm that there is evidence of a transmitting mast at the transmitter location. Note that I will not generally score a direct hit on the transmitter mast (or your house!) because the national grid refs used are only accurate to about +/- 100m.
Your aerial should be aligned on a beam heading of 108
You may need to zoom out on very long paths.
Selecting and siting your TV aerial
Why DTT is different from an analogue install