Topography with RocketPy

Hello, along this jupyter notebook we will show how RocketPy can handle with the Earth Topography. We mainly will use data provided by the NASADEM Merged DEM Global 1 arc second nc.

NASADEM is a digital elevation model based on the Shuttle Radar Topography Mission (SRTM), a collaboration between NASA and the National Geospatial-Intelligence Agency (NGA), as well as participation from the German and Italian space agencies. You can read more about NASADEM at: https://cmr.earthdata.nasa.gov/search/concepts/C1546314436-LPDAAC_ECS.html

This is a first step forward stopping consider Earth as flat and can get us much better results when we are flying next to mountains or valleys

Initialization

First of all, we import the Environment Class, which allows to set topographic profiles

from rocketpy import Environment

For example, let’s set an Environment consider a fictional launch at Switzerland. First we need to set the basic information about our Environment object

env = Environment(latitude=46.90479, longitude=8.07575, datum="WGS84")

Obs.: Notice that the datum argument is used only for the converting from geodesic (i.e. lat/lon) to UTM coordinate system.

Set topography

Now we finally set our topography

env.set_topographic_profile(
    type="NASADEM_HGT",
    file="../../data/sites/switzerland/NASADEM_NC_n46e008.nc",
    dictionary="netCDF4",
    crs=None,
)

Find the launch site elevation

Once we defined the topographic profile, we can find the launch site elevation

elevation = env.get_elevation_from_topographic_profile(env.latitude, env.longitude)

And finally set the elevation to the Environment object:

env.set_elevation(elevation)

Visualize information

Now we can see the elevation that we’ve set, as well as other important attributes of our Environment object. We do that by running the .info() method:

env.info()

Calculate Earth Radius at latitude

If we want to, we can calculate the Earth radius based on the launch site latitude

e_radius = env.calculate_earth_radius(env.latitude)

print(
    "The Earth radius at latitude {:.6f}°:  {:.2f} km".format(
        env.latitude, e_radius / 1000
    )
)