Terrain Mapping

[Marvin VE3VCG]

Plotting a path between two points for 2 meter line of sight communications is an interesting exercise. The DX commander discovered a feature in Google Earth which allows the easy creation of a terrain elevation profile between 2 points with a couple of mouse clicks. This should be very useful for those, like me with an interest in 2 meter simplex or those working 2 meter side band. This is very short but interesting illustration of how to use this handy feature.

[Richard VE3OZW]

Plotting a path between two points for 2 meter line of sight communications is an interesting exercise...

Hey Marvin, looks good.  I have been using this website that Dave Newcombe forwarded last fall.  It works very well although sadly it shows that I am pretty much trying to get through a large portion of earth to get out anywhere.

https://www.scadacore.com/tools/rf-path/...-of-sight/

[Marvin VE3VCG]

Plotting a path between two points for 2 meter line of sight communications is an interesting exercise...

Hi Richard, and thanks for the link. I saw this site in my research but didn't try using it until you shared the link. Here's the amusing result I got plotting a line roughly between Paisley and Barrie. As improbable as it seems, I can hear Barrie, although not reliably, even on my mobile. I have reasoned that, in spite of the apparent massive Escarpment between here and there, the terrain may contain valleys or gaps which allow RF to sneak through. John VE3KOT and I have had a couple of discussions about this idea. He indicated that at one of his previous locations he made use of something called the edge effect to hit a repeater which could not be reached directly. I'm not of course ruling out ducting and skip as possible explanations for hearing Barrie on 2 meters but I'm considering all possible angles (pun intended). My plot follows below.




Hey Marvin, looks good.  I have been using this website that Dave Newcombe forwarded last fall.  It works very well although sadly it shows that I am pretty much trying to get through a large portion of earth to get out anywhere.

https://www.scadacore.com/tools/rf-path/...-of-sight/

[VE3WI Dave]

Marvin your plot is hard to read, looks like an encrypted message to a spy :-)

I gave the Google Earth method a try for my QTH to VE3OSR.  See attached.

I couldn't find a way to copy the graph so I used the snipping tool & pasted it into a LibreOffice Draw page.  Had to add my mast elev. & OSR tower manually.  The app in the link I sent to Richard is designed for this purpose, so it lets you input those parameters.  I think Tom said OSR ant. was at 300' but I drew a 200' line as well.  Easy to see why my net attendance was iffy until the link came up.

EM ground waves do bend around the curvature of the earth a bit so the actual range is a little more than direct line-of-sight.

73
Dave, VE3WI

[Marvin VE3VCG]

Hi Dave and thanks for your reply.
When I did my plot I had my screen capture utility capture it to my clipboard. I though it would just paste the image into the post as one does with email. However the result obviously, was not the image but the underlying code. My apologies, but I didn't really have time to delete the post and then do it over by saving the clipped image to a proper image file then uploading that.

I will have another go at it when I get time to do it properly.

Marvin your plot is hard to read, looks like an encrypted message to a spy :-)

I gave the Google Earth method a try for my QTH to VE3OSR.  See attached.

I couldn't find a way to copy the graph so I used the snipping tool & pasted it into a LibreOffice Draw page.  Had to add my mast elev. & OSR tower manually.  The app in the link I sent to Richard is designed for this purpose, so it lets you input those parameters.  I think Tom said OSR ant. was at 300' but I drew a 200' line as well.  Easy to see why my net attendance was iffy until the link came up.

EM ground waves do bend around the curvature of the earth a bit so the actual range is a little more than direct line-of-sight.

73
Dave, VE3WI