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I followed this method from my other post [distance between a point and a curve[(find the distance between a point and a curve python) but something is wrong. The values aren't accurate.
I plotted this same trajectory in Mathematica and checked a few distances and I have found distances as low as 18000 where python is returning a minimum of 209000.
What is going wrong in the code at the bottom?
EDIT There was an error in this code everything checks out now. Thanks.
import numpy as np
from scipy.integrate import odeint
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
me = 5.974 * 10 ** (24) # mass of the earth
mm = 7.348 * 10 ** (22) # mass of the moon
G = 6.67259 * 10 ** (-20) # gravitational parameter
re = 6378.0 # radius of the earth in km
rm = 1737.0 # radius of the moon in km
r12 = 384400.0 # distance between the CoM of the earth and moon
M = me + mm
pi1 = me / M
pi2 = mm / M
mue = 398600.0 # gravitational parameter of earth km^3/sec^2
mum = G * mm # grav param of the moon
mu = mue + mum
omega = np.sqrt(mu / r12 ** 3)
nu = -129.21 * np.pi / 180 # true anomaly angle in radian
x = 327156.0 - 4671
# x location where the moon's SOI effects the spacecraft with the offset of the
# Earth not being at (0,0) in the Earth-Moon system
y = 33050.0 # y location
vbo = 10.85 # velocity at burnout
gamma = 0 * np.pi / 180 # angle in radians of the flight path
vx = vbo * (np.sin(gamma) * np.cos(nu) - np.cos(gamma) * np.sin(nu))
# velocity of the bo in the x direction
vy = vbo * (np.sin(gamma) * np.sin(nu) + np.cos(gamma) * np.cos(nu))
# velocity of the bo in the y direction
xrel = (re + 300.0) * np.cos(nu) - pi2 * r12
# spacecraft x location relative to the earth
yrel = (re + 300.0) * np.sin(nu)
# r0 = [xrel, yrel, 0]
# v0 = [vx, vy, 0]
u0 = [xrel, yrel, 0, vx, vy, 0]
def deriv(u, dt):
n1 = -((mue * (u[0] + pi2 * r12) / np.sqrt((u[0] + pi2 * r12) ** 2
+ u[1] ** 2) ** 3)
- (mum * (u[0] - pi1 * r12) / np.sqrt((u[0] - pi1 * r12) ** 2
+ u[1] ** 2) ** 3))
n2 = -((mue * u[1] / np.sqrt((u[0] + pi2 * r12) ** 2 + u[1] ** 2) ** 3)
- (mum * u[1] / np.sqrt((u[0] - pi1 * r12) ** 2 + u[1] ** 2) ** 3))
return [u[3], # dotu[0] = u[3]
u[4], # dotu[1] = u[4]
u[5], # dotu[2] = u[5]
2 * omega * u[5] + omega ** 2 * u[0] + n1, # dotu[3] = that
omega ** 2 * u[1] - 2 * omega * u[4] + n2, # dotu[4] = that
0] # dotu[5] = 0
dt = np.arange(0.0, 320000.0, 1) # 200000 secs to run the simulation
u = odeint(deriv, u0, dt)
x, y, z, x2, y2, z2 = u.T
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.plot(x, y, z)
plt.show()
my_x, my_y, my_z = (384400,0,0)
delta_x = x - my_x
delta_y = y - my_y
delta_z = z - my_z
distance = np.array([np.sqrt(delta_x ** 2 + delta_y ** 2 +
delta_z ** 2)])
print(distance.min())
Corrected code
import numpy as np
from scipy.integrate import odeint
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
me = 5.974 * 10 ** (24) # mass of the earth
mm = 7.348 * 10 ** (22) # mass of the moon
G = 6.67259 * 10 ** (-20) # gravitational parameter
re = 6378.0 # radius of the earth in km
rm = 1737.0 # radius of the moon in km
r12 = 384400.0 # distance between the CoM of the earth and moon
M = me + mm
pi1 = me / M
pi2 = mm / M
mue = 398600.0 # gravitational parameter of earth km^3/sec^2
mum = G * mm # grav param of the moon
mu = mue + mum
omega = np.sqrt(mu / r12 ** 3)
nu = -129.21 * np.pi / 180 # true anomaly angle in radian
x = 327156.0 - 4671
# x location where the moon's SOI effects the spacecraft with the offset of the
# Earth not being at (0,0) in the Earth-Moon system
y = 33050.0 # y location
vbo = 10.85 # velocity at burnout
gamma = 0 * np.pi / 180 # angle in radians of the flight path
vx = vbo * (np.sin(gamma) * np.cos(nu) - np.cos(gamma) * np.sin(nu))
# velocity of the bo in the x direction
vy = vbo * (np.sin(gamma) * np.sin(nu) + np.cos(gamma) * np.cos(nu))
# velocity of the bo in the y direction
xrel = (re + 300.0) * np.cos(nu) - pi2 * r12
# spacecraft x location relative to the earth
yrel = (re + 300.0) * np.sin(nu)
# r0 = [xrel, yrel, 0]
# v0 = [vx, vy, 0]
u0 = [xrel, yrel, 0, vx, vy, 0]
def deriv(u, dt):
n1 = -((mue * (u[0] + pi2 * r12) / np.sqrt((u[0] + pi2 * r12) ** 2
+ u[1] ** 2) ** 3)
- (mum * (u[0] - pi1 * r12) / np.sqrt((u[0] - pi1 * r12) ** 2
+ u[1] ** 2) ** 3))
n2 = -((mue * u[1] / np.sqrt((u[0] + pi2 * r12) ** 2 + u[1] ** 2) ** 3)
- (mum * u[1] / np.sqrt((u[0] - pi1 * r12) ** 2 + u[1] ** 2) ** 3))
return [u[3], # dotu[0] = u[3]
u[4], # dotu[1] = u[4]
u[5], # dotu[2] = u[5]
2 * omega * u[4] + omega ** 2 * u[0] + n1, # dotu[3] = that
omega ** 2 * u[1] - 2 * omega * u[3] + n2, # dotu[4] = that
0] # dotu[5] = 0
dt = np.arange(0.0, 320000.0, 1) # 200000 secs to run the simulation
u = odeint(deriv, u0, dt)
x, y, z, x2, y2, z2 = u.T
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.plot(x, y, z)
plt.show()
my_x, my_y, my_z = (384400,0,0)
delta_x = x - my_x
delta_y = y - my_y
delta_z = z - my_z
distance = np.array([np.sqrt(delta_x ** 2 + delta_y ** 2 +
delta_z ** 2)])
print(distance.min())
Related
To preface, I am completely new to Python and MatPlotLib, and I am working on a school project to calculate the trajectory of a satellite around the earth. I was wondering if it was possible to grab the data from every point the model calculates and put it inside the graph, plotting time on the x-axis and height on the y-axis. I tried to directly plot the two values, but it doesn't seem to appear on the graph. Is it possible to put every value from the calculations in the graph, or will I need to have a direct formula for the line to plot it in a graph.
The air resistance also changes for certain heights, so it makes it harder to make a direct formula. Here's the code, I am aware it is terribly formatted but it being my first project all I need from it is to get a t,h-graph. Thanks in advance for the help!
from typing import Any, Union
import matplotlib.pyplot as plt
import numpy as np
data = []
t = 0
dt = 10
A = 10
Cw = 2.7
h = 300000
h0 = h
G = 6.67384 * 10 ** -11
M = 5.972 * 10 ** 24
m = 209.4 * A ** (3 / 2)
r = 6371000 + h
v: Union[float, Any] = (G * M / r) ** .5
vx = v
vy = 0
Px = 0
Py = r
while 0 < h < h0 + 100000:
# for _ in range(2592000):
t = t + dt
r = (Px ** 2 + Py ** 2) ** .5
Fg = G * M * m / r ** 2
Fgx = -Fg * Px / r
Fgy = -Fg * Py / r
h = r - 6371000
if h > 600000:
z = 1.607 * 10 ** -11 * 0.991169 ** (h / 1000)
else:
if h > 139000:
z = 3.848 * 10 ** -8 * 0.978294 ** (h / 1000)
else:
z = 1.225 * 0.863697 ** (h / 1000)
v = (vx ** 2 + vy ** 2) ** .5
Fwl = 0.5 * z * Cw * A * v ** 2
Fwlx = -Fwl * vx / v
Fwly = -Fwl * vy / v
ax = (Fgx + Fwlx) / m
ay = (Fgy + Fwly) / m
vx = vx + ax * dt
vy = vy + ay * dt
Px = Px + vx * dt
Py = Py + vy * dt
data += [[h, t]]
print(h)
print(t)
fig, ax = plt.subplots()
ax.plot(t, h)
plt.show()
As suggested by Michael Szczesny in the comment, you should indent data += [[h, t]] within the while loop.
Then I suggest you to plot with:
ax.plot(*zip(*data))
in order to separate h for t and get h(t) curve.
An other suggestion is to flip the order in which you store h and t in data:
data += [[h, t]]
in this way you will get a plot of the height with respect to time (and not the inverse).
Complete Code
from typing import Any, Union
import matplotlib.pyplot as plt
data = []
t = 0
dt = 10
A = 10
Cw = 2.7
h = 300000
h0 = h
G = 6.67384 * 10 ** -11
M = 5.972 * 10 ** 24
m = 209.4 * A ** (3 / 2)
r = 6371000 + h
v: Union[float, Any] = (G * M / r) ** .5
vx = v
vy = 0
Px = 0
Py = r
while 0 < h < h0 + 100000:
# for _ in range(2592000):
t = t + dt
r = (Px ** 2 + Py ** 2) ** .5
Fg = G * M * m / r ** 2
Fgx = -Fg * Px / r
Fgy = -Fg * Py / r
h = r - 6371000
if h > 600000:
z = 1.607 * 10 ** -11 * 0.991169 ** (h / 1000)
else:
if h > 139000:
z = 3.848 * 10 ** -8 * 0.978294 ** (h / 1000)
else:
z = 1.225 * 0.863697 ** (h / 1000)
v = (vx ** 2 + vy ** 2) ** .5
Fwl = 0.5 * z * Cw * A * v ** 2
Fwlx = -Fwl * vx / v
Fwly = -Fwl * vy / v
ax = (Fgx + Fwlx) / m
ay = (Fgy + Fwly) / m
vx = vx + ax * dt
vy = vy + ay * dt
Px = Px + vx * dt
Py = Py + vy * dt
data += [[h, t]]
fig, ax = plt.subplots()
ax.plot(*zip(*data))
plt.show()
I am having trouble converting a table of Eastings/Northings co-ordinates from the British National Grid System to Latitude/Longitude co-ordinates in the WGS84 system. I have written the below set of functions with constants from the Ordnance Survey's Helmert transformation spreadsheet: https://www.ordnancesurvey.co.uk/business-government/tools-support/os-net/coordinates
import math
import pandas as pd
North = 666099.000 # Northing to be transformed
East = 253697.000 # Easting to be transformed
a = 6377563.396 # Semi-major axis for OGSB36
#a = 6378137.0000 # Semi-major axis for WGS84
b = 6356256.909 # Semi-minor axis for OGSB36
#b = 6356752.3142 # Semi-minor axis for WGS84
f0 = 0.9996012717 # Central Meridan Scale
e0 = 400000 # True origin Easting
n0 = -100000 # True origin Northing
PHI0 = 0.855211333 # True origin latitude (Radians) i.e. N 49 0' 0''
DecimalPHI0 = 49.00000000 # True origin latitude (Degrees)
LAM0 = -0.034906585 # True origin longitude (Radians) i.e. W 2 0' 0''
DecimalLAM0 = -2.00000000 # True origin longitude (Degrees)
def InitialLat(North, n0, af0, PHI0, n, bf0):
"""
Compute initial value for Latitude (PHI) IN RADIANS.
Input:
- northing of point (North) and northing of false origin (n0) in meters;
- semi major axis multiplied by central meridian scale factor (af0) in meters;
- latitude of false origin (PHI0) IN RADIANS;
- n (computed from a, b and f0) and
- ellipsoid semi major axis multiplied by central meridian scale factor (bf0) in meters.
"""
#First PHI value (PHI1)
PHI1 = ((North - n0) / af0) + PHI0
def Marc(bf0, n, PHI0, PHI1):
"""
Compute meridional arc.
Input:
- ellipsoid semi major axis multiplied by central meridian scale factor (bf0) in meters;
- n (computed from a, b and f0);
- lat of false origin (PHI0) and initial or final latitude of point (PHI) IN RADIANS.
"""
Marc = bf0 * (((1 + n + ((5 / 4) * (n ** 2)) + ((5 / 4) * (n ** 3))) * (PHI1 - PHI0))
- (((3 * n) + (3 * (n ** 2)) + ((21 / 8) * (n ** 3))) * (math.sin(PHI1 - PHI0)) * (math.cos(PHI1 + PHI0)))
+ ((((15 / 8) * (n ** 2)) + ((15 / 8) * (n ** 3))) * (math.sin(2 * (PHI1 - PHI0))) * (math.cos(2 * (PHI1 + PHI0))))
- (((35 / 24) * (n ** 3)) * (math.sin(3 * (PHI1 - PHI0))) * (math.cos(3 * (PHI1 + PHI0)))))
return Marc
# Calculate M
M = Marc(bf0, n, PHI0, PHI1)
#Calculate new PHI value (PHI2)
PHI2 = ((North - n0 - M) / af0) + PHI1
#Iterate to get final value for InitialLat
while abs(North - n0 - M) > 0.00001:
PHI2 = ((North - n0 - M) / af0) + PHI1
M = Marc(bf0, n, PHI0, PHI2)
PHI1 = PHI2
InitialLat = PHI2
return InitialLat
def E_N_to_Lat(East, North, a, b, e0, n0, f0, PHI0, LAM0):
"""
Un-project Transverse Mercator eastings and northings back to latitude.
Input:
- eastings (East) and northings (North) in meters; _
- ellipsoid axis dimensions (a & b) in meters; _
- eastings (e0) and northings (n0) of false origin in meters; _
- central meridian scale factor (f0) and _
- latitude (PHI0) and longitude (LAM0) of false origin in decimal degrees.
"""
#Convert angle measures to radians
Pi = math.pi
RadPHI0 = PHI0 * (Pi / 180)
RadLAM0 = LAM0 * (Pi / 180)
# Compute af0, bf0, e squared (e2), n and Et
af0 = a * f0
bf0 = b * f0
e2 = ((af0 ** 2) - (bf0 ** 2)) / (af0 ** 2)
n = (af0 - bf0) / (af0 + bf0)
Et = East - e0
# Compute initial value for latitude (PHI) in radians
PHId = InitialLat(North, n0, af0, RadPHI0, n, bf0)
# Compute nu, rho and eta2 using value for PHId
nu = af0 / (math.sqrt(1 - (e2 * ((math.sin(PHId)) ** 2))))
rho = (nu * (1 - e2)) / (1 - (e2 * (math.sin(PHId)) ** 2))
eta2 = (nu / rho) - 1
# Compute Latitude
VII = (math.tan(PHId)) / (2 * rho * nu)
VIII = ((math.tan(PHId)) / (24 * rho * (nu ** 3))) * (5 + (3 * ((math.tan(PHId)) ** 2)) + eta2 - (9 * eta2 * ((math.tan(PHId)) ** 2)))
IX = ((math.tan(PHId)) / (720 * rho * (nu ** 5))) * (61 + (90 * ((math.tan(PHId)) ** 2)) + (45 * ((math.tan(PHId)) ** 4)))
E_N_Lat = (180 / Pi) * (PHId - ((Et ** 2) * VII) + ((Et ** 4) * VIII) - ((Et ** 6) * IX))
return(E_N_Lat)
def E_N_to_Long(East, North, a, b, e0, n0, f0, PHI0, LAM0):
"""
Un-project Transverse Mercator eastings and northings back to longitude.
Input:
- eastings (East) and northings (North) in meters;
- ellipsoid axis dimensions (a & b) in meters;
- eastings (e0) and northings (n0) of false origin in meters;
- central meridian scale factor (f0) and
- latitude (PHI0) and longitude (LAM0) of false origin in decimal degrees.
"""
# Convert angle measures to radians
Pi = 3.14159265358979
RadPHI0 = PHI0 * (Pi / 180)
RadLAM0 = LAM0 * (Pi / 180)
# Compute af0, bf0, e squared (e2), n and Et
af0 = a * f0
bf0 = b * f0
e2 = ((af0 ** 2) - (bf0 ** 2)) / (af0 ** 2)
n = (af0 - bf0) / (af0 + bf0)
Et = East - e0
# Compute initial value for latitude (PHI) in radians
PHId = InitialLat(North, n0, af0, RadPHI0, n, bf0)
# Compute nu, rho and eta2 using value for PHId
nu = af0 / (math.sqrt(1 - (e2 * ((math.sin(PHId)) ** 2))))
rho = (nu * (1 - e2)) / (1 - (e2 * (math.sin(PHId)) ** 2))
eta2 = (nu / rho) - 1
# Compute Longitude
X = ((math.cos(PHId)) ** -1) / nu
XI = (((math.cos(PHId)) ** -1) / (6 * (nu ** 3))) * ((nu / rho) + (2 * ((math.tan(PHId)) ** 2)))
XII = (((math.cos(PHId)) ** -1) / (120 * (nu ** 5))) * (5 + (28 * ((math.tan(PHId)) ** 2)) + (24 * ((math.tan(PHId)) ** 4)))
XIIA = (((math.cos(PHId)) ** -1) / (5040 * (nu ** 7))) * (61 + (662 * ((math.tan(PHId)) ** 2)) + (1320 * ((math.tan(PHId)) ** 4)) + (720 * ((math.tan(PHId)) ** 6)))
E_N_Long = (180 / Pi) * (RadLAM0 + (Et * X) - ((Et ** 3) * XI) + ((Et ** 5) * XII) - ((Et ** 7) * XIIA))
return E_N_Long
def E_N_to_Lat_Long(North, East):
Lat = E_N_to_Lat(East,North,a,b,e0,n0,f0,DecimalPHI0,DecimalLAM0)
Long = E_N_to_Long(East,North,a,b,e0,n0,f0,DecimalPHI0,DecimalLAM0)
return [Lat, Long]
This all runs fine but it only has a conversion accuracy of +/- 3m or so which isn't good enough for the application I need it for. Is there a better alternative for converting several thousand co-ordinates using Python?
Here are a couple of python libraries for converting from WGS84 to BNG, both utilise OSTN15 for accurate conversions:
https://github.com/urschrei/convertbng
https://grid-banger.readthedocs.io/en/latest/README.html
More info from OS can be found here: https://www.ordnancesurvey.co.uk/documents/resources/guide-coordinate-systems-great-britain.pdf
I solve the motion in gravitational field around the sun with scipy and mathplotlib and have a problem. My solution is not correct. It is not like in example. Formulas that I used.
from scipy.integrate import odeint
import scipy.constants as constants
import numpy as np
import matplotlib.pyplot as plt
M = 1.989 * (10 ** 30)
G = constants.G
alpha = 30
alpha0 = (alpha / 180) * np.pi
v00 = 0.7
v0 = v00 * 1000
def dqdt(q, t):
x = q[0]
y = q[2]
ax = - G * M * (x / ((x ** 2 + y ** 2) ** 1.5))
ay = - G * M * (y / ((x ** 2 + y ** 2) ** 1.5))
return [q[1], ax, q[3], ay]
vx0 = v0 * np.cos(alpha0)
vy0 = v0 * np.sin(alpha0)
x0 = -150 * (10 ** 11)
y0 = 0 * (10 ** 11)
q0 = [x0, vx0, y0, vy0]
N = 1000000
t = np.linspace(0.0, 100000000000.0, N)
pos = odeint(dqdt, q0, t)
x1 = pos[:, 0]
y1 = pos[:, 2]
plt.plot(x1, y1, 0, 0, 'ro')
plt.ylabel('y')
plt.xlabel('x')
plt.grid(True)
plt.show()
How can I fix this?
Maybe you can tell me solution with another method for example with Euler's formula or with using other library.
I will be very greatful if you help me.
I want to "animate" a circle rolling over the sin graph, I made a code where the circle moves rapidly down a straight line, now I want the same but the acceleration will be changing.
My previous code:
import numpy as np
import matplotlib.pyplot as plt
theta = np.arange(0, np.pi * 2, (0.01 * np.pi))
x = np.arange(-50, 1, 1)
y = x - 7
plt.figure()
for t in np.arange(0, 4, 0.1):
plt.plot(x, y)
xc = ((-9.81 * t**2 * np.sin(np.pi / 2)) / 3) + (5 * np.cos(theta))
yc = ((-9.81 * t**2 * np.sin(np.pi / 2)) / 3) + (5 * np.sin(theta))
plt.plot(xc, yc, 'r')
xp = ((-9.81 * t**2 * np.sin(np.pi / 2)) / 3) + (5 * np.cos(np.pi * t))
yp = ((-9.81 * t**2 * np.sin(np.pi / 2)) / 3) + (5 * np.sin(np.pi * t))
plt.plot(xp, yp, 'bo')
plt.pause(0.01)
plt.cla()
plt.show()
You can do this by numerically integrating:
dt = 0.01
lst_x = []
lst_y = []
t = 0
while t < 10: #for instance
t += dt
a = get_acceleration(function, x)
x += v * dt + 0.5 * a * dt * dt
v += a * dt
y = get_position(fuction, x)
lst_x.append(x)
lst_y.append(y)
This is assuming the ball never leaves your slope! If it does, you'll also have to integrate in y in a similar way as done in x!!
Where your acceleration is going to be equal to g * cos(slope).
How can I find the closet distance between my trajectory and (384400,0,0)?
Also, how can I the distance from (384400,0,0) to the path at time t = 197465?
I understand that the arrays have the data but is there a way to have it check the distance of all the points (x,y,z) and return what I am looking for?
import numpy as np
from scipy.integrate import odeint
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
me = 5.974 * 10 ** (24) # mass of the earth
mm = 7.348 * 10 ** (22) # mass of the moon
G = 6.67259 * 10 ** (-20) # gravitational parameter
re = 6378.0 # radius of the earth in km
rm = 1737.0 # radius of the moon in km
r12 = 384400.0 # distance between the CoM of the earth and moon
M = me + mm
pi1 = me / M
pi2 = mm / M
mue = 398600.0 # gravitational parameter of earth km^3/sec^2
mum = G * mm # grav param of the moon
mu = mue + mum
omega = np.sqrt(mu / r12 ** 3)
nu = -129.21 * np.pi / 180 # true anomaly angle in radian
x = 327156.0 - 4671
# x location where the moon's SOI effects the spacecraft with the offset of the
# Earth not being at (0,0) in the Earth-Moon system
y = 33050.0 # y location
vbo = 10.85 # velocity at burnout
gamma = 0 * np.pi / 180 # angle in radians of the flight path
vx = vbo * (np.sin(gamma) * np.cos(nu) - np.cos(gamma) * np.sin(nu))
# velocity of the bo in the x direction
vy = vbo * (np.sin(gamma) * np.sin(nu) + np.cos(gamma) * np.cos(nu))
# velocity of the bo in the y direction
xrel = (re + 300.0) * np.cos(nu) - pi2 * r12
# spacecraft x location relative to the earth
yrel = (re + 300.0) * np.sin(nu)
# r0 = [xrel, yrel, 0]
# v0 = [vx, vy, 0]
u0 = [xrel, yrel, 0, vx, vy, 0]
def deriv(u, dt):
n1 = -((mue * (u[0] + pi2 * r12) / np.sqrt((u[0] + pi2 * r12) ** 2
+ u[1] ** 2) ** 3)
- (mum * (u[0] - pi1 * r12) / np.sqrt((u[0] - pi1 * r12) ** 2
+ u[1] ** 2) ** 3))
n2 = -((mue * u[1] / np.sqrt((u[0] + pi2 * r12) ** 2 + u[1] ** 2) ** 3)
- (mum * u[1] / np.sqrt((u[0] - pi1 * r12) ** 2 + u[1] ** 2) ** 3))
return [u[3], # dotu[0] = u[3]
u[4], # dotu[1] = u[4]
u[5], # dotu[2] = u[5]
2 * omega * u[5] + omega ** 2 * u[0] + n1, # dotu[3] = that
omega ** 2 * u[1] - 2 * omega * u[4] + n2, # dotu[4] = that
0] # dotu[5] = 0
dt = np.arange(0.0, 320000.0, 1) # 200000 secs to run the simulation
u = odeint(deriv, u0, dt)
x, y, z, x2, y2, z2 = u.T
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.plot(x, y, z)
plt.show()
To find the distance along each point in the trajectory:
my_x, my_y, my_z = (384400,0,0)
delta_x = x - my_x
delta_y = y - my_y
delta_z = z - my_z
distance = np.sqrt(np.power(delta_x, 2) +
np.power(delta_y, 2) +
np.power(delta_z, 2))
And then to find the min and that specific distance:
i = np.argmin(distance)
t_min = i / UNITS_SCALE # I can't tell how many units to a second. Is it 1.6?
d_197465 = distance[int(197465 * UNITS_SCALE)]
PS, I'm no rocket scientist, and thus haven't actually checked the stuff above x, y, z, x2, y2, z2 = u.T. I'm assuming that those are your trajectory's position and velocity?