Google Earth KML - kml

Question

How do you links cities with a curve (line) in kml for Google Earth?

Answer 1

First, since you are on SO I'm assuming you are asking from a KML perspective and not just in the desktop application.
You would need to have the coordinates of the two cities. Then you would create a kml document like the following from the docs using your coordinates in the coordinates element (note that you don't need the "LookAt" element, but it will bring your camera to the relevant area):
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
<name>LineString.kml</name>
<open>1</open>
<LookAt>
<longitude>-122.36415</longitude>
<latitude>37.824553</latitude>
<altitude>0</altitude>
<range>150</range>
<tilt>50</tilt>
<heading>0</heading>
</LookAt>
<Placemark>
<name>unextruded</name>
<LineString>
<extrude>1</extrude>
<tessellate>1</tessellate>
<coordinates>
-122.364383,37.824664,0 -122.364152,37.824322,0
</coordinates>
</LineString>
</Placemark>
<Placemark>
<name>extruded</name>
<LineString>
<extrude>1</extrude>
<tessellate>1</tessellate>
<altitudeMode>relativeToGround</altitudeMode>
<coordinates>
-122.364167,37.824787,50 -122.363917,37.824423,50
</coordinates>
</LineString>
</Placemark>
</Document>
</kml>
If you don't have the city altitudes then leave them out and be sure to set the altitudeMode element to "clampToGround" and likely the tesselate element to "1" (meaning true). If you forget this your lines may disappear underground.