Is it possible to overlay a Google Maps image over top a landscape so that I can lay out the roads/buildings to exact scale? For example, if I have a top-down image from Google Maps like the one below, how could I do this?
Sure, just hook up the texture sampler to a landscape coordinate and set it to the same size as your landscape.
Could you explain more about " hook up the texture sampler to a landscape coordinate ", please~
You might want to read some basic landscape tutorials. Read the docs and such.
Thanks!I have found a way to figure out.
Can you share it please?
You’d be better off using OpenStreetMap data, I think there’s already plug-ins for it.
Before asking most basic question it would be advisable to first look into documentation otherwise one sound just plain dead lazy and unprofessional… What the heck is wrong with this generation! Everyone just crying about giving them solutions without ANY previous effort. 
Sound like there was a lot of helping here…
Well I still have the same question.
I can get it into the map but is it possible to blend the photo into the landscape height map?
A flat photo is easy, but not when I add a height map.
(BTW, I have completed the ue4 Manual)
Cheers
Set map image to the emissive output on the landscape material and match the texture coord sizes using tex coord node.
you can add a multiplier between the texture and emissive to control brightness 1 plus is brighter, less than 1 darker.
Your map image will have to match the terrain size (tile size)
Paul G
PS, Gogle images are good for using this tecnique for hedge lines wooded areas etc,
but for roads and rivers I use a map image as the stand out much clearer
In the UK we can get map images that match grid tiles exactly.
Yes, thank you 
Will test when I got home.
Height data is from a local Lidar scanner, 0,25m detail.
And the roads I can get in many different vector format (will test them today) .
But I still need info from House placement and other details.
An overlay from a map would help me to find the exact location. But the moment I sculpt the landscape the photo dissapair.
Have been working around the clock for 3 weeks now. Almost manage everything I set for my goal, but still some small details left.
Have never been using Ue4 before, but I have read every manual and seen a lot of YouTube tutorials.
Another tip
I put the greyscale height map into Photoshop add a layer of map
Manipulate By pressing CNTR+T but hold down the shift key as you are scaling so as to keep square
Repeat for Google image using trans in layers to align details
Once done crop to size and export Height , Map and GE Image for inclusion in UE4.
Further you can make a roads mask and use this to apply an asphalt material automatically along the roads.
Similarly with river beds make a white image with black rivers and put in a layer above the heightmap then set to multiply and it will lowere the river beds in the heightmap
Paul G