From GridLAB-D Wiki
kmlfile - Specify the file to which KML (Google Earth) data is written
Synopsis
host% gridlabd -D kmlfile="gridlabd.kml" host% gridlabd --define kmlfile="gridlabd.kml" #set kmlfile="gridlabd.kml"
Description
Certain modules support KML output to support Google Earth viewing of GridLAB-D output. When the variable kmlfile is set, the KML data from supported modules will be output to the specified file.