KMLPlus 2.0.2

A Python library for creating 3d floating polygons and circles in .kml for Google Earth.

KML+

KML+ (KMLPlus) is library of code for Python which allows the user to easily create standard and 'floating' Polygons, Circles and Arcs.

Who is this for

This is for anyone who wishes to easily render polygons, especially 'floating' or curved polygons within Google Earth.

I work in the aviation industry and needed a reliable way to create models of our airspace. It its useful for creating models of airways and controlled airspace. It can be used for anything that takes your fancy!

Installing

pip

pip install kmlplus

clone

git clone https://github.com/MHenderson1988/kmlplus.git

# Or

git clone [e-mail]:MHenderson1988/kmlplus.git

Running tests

python -m unittest

Usage

Recommendations

KML+ easily integrates with the fantastic Simplekml library and I highly recommend using it in conjunction with KML+ for the best experience.

Take a look at the example .py file provided to see how KML+ integrates with SimpleKML to create airspace representations from CAA AIP supplied data.

Quick Start

The simplest way to create a standard floating polygon

import simplekml
from kmlplus import paths

# Auto generate a linepath polygon from a list of string representations of coordinates in latitude, longitude, height
# format.  Can be a mix of DMS and decimal.  Make sure the last and first coordinate are the same, otherwise the
# Polygon will not complete
list_of_coordinates = ["55.123, -4.123", "55.600, -41232.12", "55.100, -4.4323", "55.123, -4.123"]

# Pass the list to the LinePath constructor.  You can override the height at this point with the 'height' kwarg.
lower_layer = paths.LinePath(*list_of_coordinates, height=3000)

# Create the upper layer at 800m, and fill in the sides between the two
upper_layer, sides = lower_layer.create_layer_and_sides(height=10000)

# Use simplekml to create the .kml
def create_kml():
    kml = simplekml.Kml()
    fol = kml.newfolder(name='Quick start example')

    pol = fol.newpolygon()
    pol.outerboundaryis = lower_layer
    pol.altitudemode = simplekml.AltitudeMode.relativetoground

    pol = fol.newpolygon()
    pol.outerboundaryis = upper_layer
    pol.altitudemode = simplekml.AltitudeMode.relativetoground

    for item in sides:
        pol = fol.newpolygon()
        pol.outerboundaryis = item
        pol.altitudemode = simplekml.AltitudeMode.relativetoground

    kml.save('Quick start example.kml')


if __name__ == "__main__":
    create_kml()

Classes

KML+ comprises three classes -

• Coordinate class
• LinePath class
• ArcPath class

The user should be able to create simple floating polygons without touching the ArcPath class however it is documented here in case you should wish to use it in other ways.

---

Coordinate

Coordinate(**args, name=None, arc_direction=None, arc_origin=None*)

The Coordinate class accepts up to three arguments - latitude, longitude and height. This can be given as either one string or three separate arguments. Latitude and longitude must be either decimal coordinates or degrees minutes seconds (DMS). The coordinate object will auto-detect the coordinate type and will automatically convert DMS coordinates to kml readable decimal coordinates.

Coordinate instances can also be designated as the start point of a clockwise or anti-clockwise arc/circle. This is achieved by appending either 'a' or 'c' to end of the latitude or longitude value.

Examples -

from kmlplus import coordinates

# A standard coordinate object with a default height of 0
c1 = coordinates.Coordinate(55.123, -4.1234)

# The same coordinate initialised with a height of 50m
c1 = coordinates.Coordinate(55.123, -4.1234, 50)

# Now with a string
c1 = coordinates.Coordinate("55.123, -4.1234")

# Specifying that this coordinate is the start of a clockwise 'arc'
c1 = coordinates.Coordinate(55.123, '-4.1234c')

# You can combine coordinate types
c1 = coordinates.Coordinate(55.123, '-41232.327847834c')

A note on arcs -

• Values must be passed as a String eg - "55.22132c" is valid, 55.22132c will throw an error

• If kwarg arc_origin is not passed, it will default to the centroid of the LineString created later on.

---

LinePath

The LinePath class takes Coordinate objects or lists of Coordinate objects as its arguments. If a Coordinate object defines itself as the start of a clockwise or anticlockwise arc, the LinePath class will call an ArcPath instance. This will automatically create the required arc as part of the LinePath objects coordinates.

LinePath(*args, sort=False, height=None, arc_points=50, origin = self.centroid*)

*args must all be instances of Type Coordinate.

sort=True will sort the Coordinate objects into anticlockwise order around the polygon's centroid therefore allowing correct rendering by Google Earth. This is experimental and is highly unlikely to work with concave polygons.

height=float or int will override all height values in the Coordinate arguments.

arc_points=int will define how many coordinates should be created for any detected arcs/circles.

origin=Coordinate details the origin for all ArcPaths automatically generated by the LinePath. Defaults to the LinePath centroid.

from kmlplus import paths
my_line_path = paths.Linepath(coordinate_1, coordinate_2, *arcpath_1)

If a coordinate is detected with an arc suffic 'c' or 'a', the LinePath will automatically call the ArcPath class and populate the arc coordinates.

Creating a polygon using the LinePath class

Note - LinePath.sides has been deprecated since 2.0. You can now create the sides using the .create_sides() method which returns a list. Or call .create_layer_and_sides() method to create an upper layer and the sides simultaneously

Once you have created the lower layer of your polygon, you can interpolate the upper layer and generate the sides by calling the create_layer_and_sides() method -

my_line_path = paths.Linepath(coordinate_1, coordinate_2, *arcpath_1)
upper_layer, sides = my_line_path.create_layer_and_sides(height=height_for_upper_layer, origin=ArcPath_origin_coordinates)

Automatically create LinePath objects without Coordinate objects.

LinePaths and their Coordinate instances can be automatically created from a list, as in the example file provided.

frz_ref_point = coordinates.Coordinate(55.509392, -4.594581)
cta_1 = [
    "554023,-45040", "553734,-44227a", "552811,-44906", "553124,-45830", "554023,-45040"
]

def create_polygon(a_list, lower_height, upper_height, arc_origin, **kwargs):
    lp = paths.LinePath(*a_list, height=lower_height, origin=arc_origin)
    lp2, sides = lp.create_layer_and_sides(height=upper_height, origin=arc_origin)
    return lp, lp2, sides

ArcPath

ArcPath(*origin, start_bearing, end_bearing, radius, height=self.origin.height, direction='Clockwise', points=50*)

ArcPath objects are used to create a series of Coordinate objects to simulate a circle or arc which starts and ends on a specified bearing from a specified origin at a given radius. They can be 'Clockwise' or 'Anticlockwise' and return as many or as few 'points' as desired.

Acknowledgements

• Simplekml - for creating an awesome library which has helped me create many things and also inspiring me to write this library.`