Path profiles from Google Earth
Sometimes its really useful to see if there is high ground blocking the path to another amateur. You can do this easily and for free using Google Earth Pro, which is free.
Here’s an example profile showing the path between my QTH and a club member in High Wycombe. You’ll notice that there is quite a lot of solid ground between us. I’m at 3.4m ASL and the highest point is 153m ASL
To be able to see path profiles youself, simply follow these steps:
1 Install Google Earth Pro.
2 Search for one end, click drawing pin button to set a marker, drag into correct position and label if desired.
3 Ditto for the other end.
4 Zooming out so you can see both is convenient if they’re not too far apart.
4 Click the ‘Add path’ button.
5 Click on the first marker.
6 Click on the second marker and a path line will appear.
7 Right click on the path line and select ‘Show elevation profile’. The path profile will appear at the bottom of the screen.
8 If you move your cursor across the profile diagram it will show you the ground height wherever the cursor is. You’ll also see a red arrow on the path showing the location on the map. You can see the distance from the first marker along the bottom of the diagram.
9 DON’T take the profiles too literally. RF bends somewhat around the earth. (RF planners ‘flatten’ the earth’s curvature by about 30% to take this into account when working out coverage from a VHF/UHF transmitter.) Additionally you get diffration from edges, particularly useful if there is a metal-clad building or a radio/tv/mobile mast on high ground.
10 Also remember that Google uses ground level, not antenna height to show you the profile. You can see how much ground is in the way of the actual path by pasting a screenshot into Paint and drawing a straight line on the path diagram from actual antenna height (typically 8-10m) above each end point.
Let me know if you find out anything interesting!