Te copio el codigo de un kml de una ruta. Lo he sacado de aquí:
Como Crear Rutas con Google Earth
Quote::
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.2">
<Document>
<name>Paseo por Leon - Ruta.kmz</name>
<Style id="sh_ylw-pushpin">
<IconStyle>
<scale>1.3</scale>
<Icon>
<href>http://maps.google.com/mapfiles/kml/pushpin/ylw-pushpin.png</href>
</Icon>
<hotSpot x="20" y="2" xunits="pixels" yunits="pixels"/>
</IconStyle>
</Style>
<StyleMap id="msn_ylw-pushpin">
<Pair>
<key>normal</key>
<styleUrl>#sn_ylw-pushpin</styleUrl>
</Pair>
<Pair>
<key>highlight</key>
<styleUrl>#sh_ylw-pushpin</styleUrl>
</Pair>
</StyleMap>
<Style id="sn_ylw-pushpin">
<IconStyle>
<scale>1.1</scale>
<Icon>
<href>http://maps.google.com/mapfiles/kml/pushpin/ylw-pushpin.png</href>
</Icon>
<hotSpot x="20" y="2" xunits="pixels" yunits="pixels"/>
</IconStyle>
</Style>
<Placemark>
<name>Paseo por Leon</name>
<description>https://www.google-earth.es</description>
<LookAt>
<longitude>-5.568323425230737</longitude>
<latitude>42.59900866313162</latitude>
<altitude>0</altitude>
<range>767.3312473083184</range>
<tilt>5.498662558436253e-012</tilt>
<heading>-0.001210494009217888</heading>
</LookAt>
<styleUrl>#msn_ylw-pushpin</styleUrl>
<LineString>
<tessellate>1</tessellate> <coordinates>
-5.56591745418784,42.59948165729505,0 -5.565884292574538,42.59916663422388,0 -5.566723703760033,42.59895634061504,0 -5.567154398843386,42.59881049323271,0 -5.567124586069625,42.59831940816778,0 -5.566732152378564,42.59726479006807,0 -5.566905714867076,42.59733055525519,0 -5.567520568445588,42.59718869880395,0 -5.567878389471375,42.59801033382907,0 -5.568767448869636,42.59842756284672,0 -5.570283689497103,42.59805008253569,0 -5.571422068180823,42.59799595702732,0 -5.571492801088979,42.5984761995627,0 -5.570666786714341,42.5988835293187,0 -5.571166039369246,42.59989564689277,0 -5.571966789814455,42.60164360937158,0 -5.57199875200648,42.60225897799297,0 </coordinates></LineString>
</Placemark>
</Document>
</kml>
En negrita te he marcado las coordenadas de los puntos que forman la ruta
Observa que es un objeto "LineString".
Sustituye lo que necesites en tu ruta.