Turbo-Arrow-Driver
Pre-takeoff checklist
As part of a discussion of an accident (see here https://www.pilotsofamerica.com/com...ort-of-burley-municipal-airport.137623/page-3), I created a KML file for Google Earth (GE) which depicts the waypoints on an instrument approach in 3D to better visualize what some of the issues are with the approach.
Some folks wanted to know how to create a KML file like this, so here's the method I used. Hope you find this useful!
Some of this, especially coordinate calculations, will be easier with the aid of some kind of scripted computer programming application, such as perl, excel, python, octave/matlab, etc. Whatever you are comfortable with. Or just a plain old calculator will do in a pinch.
Coordinates and elevations should be obtained from the FAA. For waypoints, search online for "FAA Waypoint Database". The current URL for this page is
https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/Loc_ID_Search/Fixes_Waypoints/
but that may change, so use the online search if the link doesn't work.
For airports, search online for "FAA Airport Database", and the current link for this is
https://www.faa.gov/air_traffic/flight_info/aeronav/Aero_Data/Airport_Data/
Presumably, you're wanting the coordinates at the end of a runway, and these are listed for all runways. In most cases, the elevation of the runway end should be used, not the published TDZE. If there is a displaced threshold, those coordinates are also published as "DT Latitude", etc. Be sure to add the TCH to runway end elevation if that's important for the image. Note that the FAA seems to compute descent angles using the elevation at the runway end or threshold -- not TDZE.
FAA publishes lat/lon data as degrees, minutes and seconds, but KML requires decimal degrees and so the FAA data must be converted -- a precision of 6 decimal places s/b adequate. This can be tedious without some sort of computer program and that's beyond the scope here. There are lots of online explanations of how to make this conversion.
Coordinates are entered in the KML file as three numbers separated by commas: longitude, latitude and elevation. Longitude is positive east of Greenwich, so airports in the CONUS will have negative longitudes. KML files require altitude in meters, so don't forget to convert MSL altitudes in feet to meters.
Below is a KML file for the last three waypoints of the N23 RNAV-7 approach (Sydney, NY). You can use this example as a template. Simply replace the numeric coordinates with those for your project. If you want to learn more about KML, this is a good starting place, too. I'm not really happy with the labels in GE, so the points are not labeled, and those need to be added in photo-editing software after saving the image (if you want them labeled).
Two "Style" elements are defined -- one for the glide path (GP) and one for the MDA. These are just arbitrary names and don't mean anything special to GE. The color of the MDA style (600000ff) is red, but partially transparent. The color is a hexadecimal value specifying (in order) opacity, blue, green and red values: OOBBGGRR where each two letter item is a value between 00 and FF.
Each display object is a "Placemark" consisting of one "LineString". The "extrude" option in the first object causes the vertical wall to be displayed below the glide path. The "absolute" setting for "altitudeMode" tells GE that elevations are relative to MSL.
The black line at MDA is generated by taking the lat/lon coordinates of the last stepdown fix and runway end, and specifying the same MSL altitude (equal to the MDA) for each of the two points.
When using the web interface (earth.google.com), the KML file can be loaded by clicking on the "Projects" button, then click "Open" and select "Import KML file from computer" from the drop-down list. Once the file is loaded, experiment with different view angles and heights to highlight whatever it is you're trying to depict.
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
<Style id="MDA"><LineStyle><color>ff000000</color></LineStyle></Style>
<Style id="GP">
<LineStyle><color>ff0000ff</color></LineStyle>
<PolyStyle><color>600000ff</color></PolyStyle>
</Style>
<Placemark>
<styleUrl>#GP</styleUrl>
<LineString>
<extrude>1</extrude>
<altitudeMode>absolute</altitudeMode>
<coordinates>
-75.614203,42.209608,1097
-75.519383,42.254150,823
-75.422528,42.299502,325
</coordinates>
</LineString>
</Placemark>
<Placemark>
<styleUrl>#MDA</styleUrl>
<LineString>
<altitudeMode>absolute</altitudeMode>
<coordinates>
-75.519383,42.254150,652
-75.422528,42.299502,652
</coordinates>
</LineString>
</Placemark>
</Document>
</kml>
Some folks wanted to know how to create a KML file like this, so here's the method I used. Hope you find this useful!
Some of this, especially coordinate calculations, will be easier with the aid of some kind of scripted computer programming application, such as perl, excel, python, octave/matlab, etc. Whatever you are comfortable with. Or just a plain old calculator will do in a pinch.
Coordinates and elevations should be obtained from the FAA. For waypoints, search online for "FAA Waypoint Database". The current URL for this page is
https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/Loc_ID_Search/Fixes_Waypoints/
but that may change, so use the online search if the link doesn't work.
For airports, search online for "FAA Airport Database", and the current link for this is
https://www.faa.gov/air_traffic/flight_info/aeronav/Aero_Data/Airport_Data/
Presumably, you're wanting the coordinates at the end of a runway, and these are listed for all runways. In most cases, the elevation of the runway end should be used, not the published TDZE. If there is a displaced threshold, those coordinates are also published as "DT Latitude", etc. Be sure to add the TCH to runway end elevation if that's important for the image. Note that the FAA seems to compute descent angles using the elevation at the runway end or threshold -- not TDZE.
FAA publishes lat/lon data as degrees, minutes and seconds, but KML requires decimal degrees and so the FAA data must be converted -- a precision of 6 decimal places s/b adequate. This can be tedious without some sort of computer program and that's beyond the scope here. There are lots of online explanations of how to make this conversion.
Coordinates are entered in the KML file as three numbers separated by commas: longitude, latitude and elevation. Longitude is positive east of Greenwich, so airports in the CONUS will have negative longitudes. KML files require altitude in meters, so don't forget to convert MSL altitudes in feet to meters.
Below is a KML file for the last three waypoints of the N23 RNAV-7 approach (Sydney, NY). You can use this example as a template. Simply replace the numeric coordinates with those for your project. If you want to learn more about KML, this is a good starting place, too. I'm not really happy with the labels in GE, so the points are not labeled, and those need to be added in photo-editing software after saving the image (if you want them labeled).
Two "Style" elements are defined -- one for the glide path (GP) and one for the MDA. These are just arbitrary names and don't mean anything special to GE. The color of the MDA style (600000ff) is red, but partially transparent. The color is a hexadecimal value specifying (in order) opacity, blue, green and red values: OOBBGGRR where each two letter item is a value between 00 and FF.
Each display object is a "Placemark" consisting of one "LineString". The "extrude" option in the first object causes the vertical wall to be displayed below the glide path. The "absolute" setting for "altitudeMode" tells GE that elevations are relative to MSL.
The black line at MDA is generated by taking the lat/lon coordinates of the last stepdown fix and runway end, and specifying the same MSL altitude (equal to the MDA) for each of the two points.
When using the web interface (earth.google.com), the KML file can be loaded by clicking on the "Projects" button, then click "Open" and select "Import KML file from computer" from the drop-down list. Once the file is loaded, experiment with different view angles and heights to highlight whatever it is you're trying to depict.
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
<Style id="MDA"><LineStyle><color>ff000000</color></LineStyle></Style>
<Style id="GP">
<LineStyle><color>ff0000ff</color></LineStyle>
<PolyStyle><color>600000ff</color></PolyStyle>
</Style>
<Placemark>
<styleUrl>#GP</styleUrl>
<LineString>
<extrude>1</extrude>
<altitudeMode>absolute</altitudeMode>
<coordinates>
-75.614203,42.209608,1097
-75.519383,42.254150,823
-75.422528,42.299502,325
</coordinates>
</LineString>
</Placemark>
<Placemark>
<styleUrl>#MDA</styleUrl>
<LineString>
<altitudeMode>absolute</altitudeMode>
<coordinates>
-75.519383,42.254150,652
-75.422528,42.299502,652
</coordinates>
</LineString>
</Placemark>
</Document>
</kml>
