nyx_space/io/gravity.rs
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/*
Nyx, blazing fast astrodynamics
Copyright (C) 2018-onwards Christopher Rabotin <christopher.rabotin@gmail.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
use crate::linalg::DMatrix;
use crate::NyxError;
use flate2::read::GzDecoder;
use std::fs::File;
use std::io::prelude::*;
use std::str::FromStr;
/// `HarmonicsMem` loads the requested gravity potential files and stores them in memory (in a HashMap).
///
/// WARNING: This memory backend may require a lot of RAM (e.g. EMG2008 2190x2190 requires nearly 400 MB of RAM).
#[derive(Clone)]
pub struct HarmonicsMem {
degree: usize,
order: usize,
c_nm: DMatrix<f64>,
s_nm: DMatrix<f64>,
}
impl HarmonicsMem {
/// Initialize `HarmonicsMem` with a custom J2 value
pub fn from_j2(j2: f64) -> HarmonicsMem {
let mut c_nm = DMatrix::from_element(3, 3, 0.0);
c_nm[(2, 0)] = j2;
HarmonicsMem {
degree: 2 + 1,
order: 0,
c_nm,
s_nm: DMatrix::from_element(3, 3, 0.0),
}
}
/// Initialize `HarmonicsMem` as an EARTH J<sub>2</sub> only using the JGM3 model (available in GMAT)
///
/// Use the embedded Earth parameter. If others are needed, load from `from_shadr` or `from_egm`.
/// *WARNING:* This is an EARTH gravity model, and _should not_ be used around any other body.
pub fn j2_jgm3() -> HarmonicsMem {
Self::from_j2(-4.841_653_748_864_70e-04)
}
/// Initialize `HarmonicsMem` as an EARTH J<sub>2</sub> only using the JGM2 model (available in GMAT)
///
/// Use the embedded Earth parameter. If others are needed, load from `from_shadr` or `from_egm`.
/// *WARNING:* This is an EARTH gravity model, and _should not_ be used around any other body.
pub fn j2_jgm2() -> HarmonicsMem {
Self::from_j2(-4.841_653_9e-04)
}
/// Initialize `HarmonicsMem` as J<sub>2</sub> only using the EGM2008 model (from the GRACE mission, best model as of 2018)
///
/// *WARNING:* This is an EARTH gravity model, and _should not_ be used around any other body.
pub fn j2_egm2008() -> HarmonicsMem {
Self::from_j2(-0.484_165_143_790_815e-03)
}
/// Initialize `HarmonicsMem` from the file path (must be a gunzipped file)
///
/// Gravity models provided by `nyx`:
/// + EMG2008 to 2190 for Earth (tide free)
/// + Moon to 1500 (from SHADR file)
/// + Mars to 120 (from SHADR file)
/// + Venus to 150 (from SHADR file)
pub fn from_shadr(
filepath: &str,
degree: usize,
order: usize,
gunzipped: bool,
) -> Result<HarmonicsMem, NyxError> {
Self::load(
gunzipped, true, //SHADR has a header which we ignore
degree, order, filepath,
)
}
pub fn from_egm(
filepath: &str,
degree: usize,
order: usize,
gunzipped: bool,
) -> Result<HarmonicsMem, NyxError> {
Self::load(gunzipped, false, degree, order, filepath)
}
pub fn from_cof(
filepath: &str,
degree: usize,
order: usize,
gunzipped: bool,
) -> Result<HarmonicsMem, NyxError> {
let mut f = File::open(filepath).map_err(|_| NyxError::FileUnreadable {
msg: format!("File not found: {filepath}"),
})?;
let mut buffer = vec![0; 0];
if gunzipped {
let mut d = GzDecoder::new(f);
d.read_to_end(&mut buffer)
.map_err(|_| NyxError::FileUnreadable {
msg: "could not read file as gunzip".to_string(),
})?;
} else {
f.read_to_end(&mut buffer)
.map_err(|_| NyxError::FileUnreadable {
msg: "could not read file to end".to_string(),
})?;
}
let data_as_str = String::from_utf8(buffer).map_err(|_| NyxError::FileUnreadable {
msg: "could not decode file contents as utf8".to_string(),
})?;
// Since the COF files are so specific, we just code everything up in here.
let mut c_nm_mat = DMatrix::from_element(degree + 1, degree + 1, 0.0);
let mut s_nm_mat = DMatrix::from_element(degree + 1, degree + 1, 0.0);
let mut max_order: usize = 0;
let mut max_degree: usize = 0;
for (lno, line) in data_as_str.split('\n').enumerate() {
if line.is_empty() || !line.starts_with('R') {
continue; // This is either a comment, a header or "END"
}
// These variables need to be declared as mutable because rustc does not know
// we nwon't match each ino more than once.
let mut cur_degree: usize = 0;
let mut cur_order: usize = 0;
let mut c_nm: f64 = 0.0;
let mut s_nm: f64 = 0.0;
for (ino, item) in line.split_whitespace().enumerate() {
match ino {
0 => continue, // We need this so we don't break at every first item
1 => match usize::from_str(item) {
Ok(val) => cur_degree = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse degree `{item}` on line {lno}"
),
});
}
},
2 => match usize::from_str(item) {
Ok(val) => cur_order = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse order `{item}` on line {lno}"
),
});
}
},
3 => {
// If we are at degree zero, then there is only one item, so we can parse that and
// set the S_nm to zero.
if degree == 0 {
s_nm = 0.0;
match f64::from_str(item) {
Ok(val) => c_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse C_nm `{item}` on line {lno}"
),
});
}
}
} else {
// There is a space as a delimiting character between the C_nm and S_nm only if the S_nm
// is a positive number, otherwise, they are continuous (what a great format).
if (item.matches('-').count() == 3 && !item.starts_with('-'))
|| item.matches('-').count() == 4
{
// Now we have two items concatenated into one... great
let parts: Vec<&str> = item.split('-').collect();
if parts.len() == 5 {
// That mean we have five minus signs, so both the C and S are negative.
let c_nm_str = "-".to_owned() + parts[1] + "-" + parts[2];
match f64::from_str(&c_nm_str) {
Ok(val) => c_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse C_nm `{item}` on line {lno}"
),
});
}
}
// That mean we have five minus signs, so both the C and S are negative.
let s_nm_str = "-".to_owned() + parts[3] + "-" + parts[4];
match f64::from_str(&s_nm_str) {
Ok(val) => s_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse S_nm `{item}` on line {lno}"
),
});
}
}
} else {
// That mean we have fouve minus signs, and since both values are concatenated, C_nm is positive and S_nm is negative
let c_nm_str = parts[0].to_owned() + "-" + parts[1];
match f64::from_str(&c_nm_str) {
Ok(val) => c_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse C_nm `{item}` on line {lno}"
),
});
}
}
// That mean we have five minus signs, so both the C and S are negative.
let s_nm_str = "-".to_owned() + parts[2] + "-" + parts[3];
match f64::from_str(&s_nm_str) {
Ok(val) => s_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse S_nm `{item}` on line {lno}"
),
});
}
}
}
} else {
// We only have the first item, and that's the C_nm
match f64::from_str(item) {
Ok(val) => c_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse C_nm `{item}` on line {lno}"
),
});
}
}
}
}
}
4 => match f64::from_str(item) {
// If this exists, then the S_nm is positive.
Ok(val) => s_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse S_nm `{item}` on line {lno}"
),
});
}
},
_ => break, // We aren't storing the covariance of these harmonics
}
}
if cur_degree > degree {
// The file is organized by degree, so once we've passed the maximum degree we want,
// we can safely stop reading the file.
break;
}
// Only insert this data into the hashmap if it's within the required order as well
if cur_order <= order {
c_nm_mat[(cur_degree, cur_order)] = c_nm;
s_nm_mat[(cur_degree, cur_order)] = s_nm;
}
// This serves as a warning.
max_order = if cur_order > max_order {
cur_order
} else {
max_order
};
max_degree = if cur_degree > max_degree {
cur_degree
} else {
max_degree
};
}
if max_degree < degree || max_order < order {
warn!(
"{} only contained (degree, order) of ({}, {}) instead of requested ({}, {})",
filepath, max_degree, max_order, degree, order
);
} else {
info!(
"{} loaded with (degree, order) = ({}, {})",
filepath, degree, order
);
}
Ok(HarmonicsMem {
degree: max_degree,
order: max_order,
c_nm: c_nm_mat,
s_nm: s_nm_mat,
})
}
/// `load` handles the actual loading in memory.
fn load(
gunzipped: bool,
skip_first_line: bool,
degree: usize,
order: usize,
filepath: &str,
) -> Result<HarmonicsMem, NyxError> {
let mut f = File::open(filepath).map_err(|_| NyxError::FileUnreadable {
msg: format!("File not found: {filepath}"),
})?;
let mut buffer = vec![0; 0];
if gunzipped {
let mut d = GzDecoder::new(f);
d.read_to_end(&mut buffer)
.map_err(|_| NyxError::FileUnreadable {
msg: "could not read file as gunzip".to_string(),
})?;
} else {
f.read_to_end(&mut buffer)
.map_err(|_| NyxError::FileUnreadable {
msg: "could not read file to end".to_string(),
})?;
}
let data_as_str = String::from_utf8(buffer).map_err(|_| NyxError::FileUnreadable {
msg: "could not decode file contents as utf8".to_string(),
})?;
let mut c_nm_mat = DMatrix::from_element(degree + 1, degree + 1, 0.0);
let mut s_nm_mat = DMatrix::from_element(degree + 1, degree + 1, 0.0);
let mut max_degree: usize = 0;
let mut max_order: usize = 0;
for (lno, line) in data_as_str.split('\n').enumerate() {
if lno == 0 && skip_first_line {
continue;
}
// These variables need to be declared as mutable because rustc does not know
// we won't match each ino more than once.
let mut cur_order: usize = 0;
let mut cur_degree: usize = 0;
let mut c_nm: f64 = 0.0;
let mut s_nm: f64 = 0.0;
for (ino, item) in line.replace(',', " ").split_whitespace().enumerate() {
match ino {
0 => match usize::from_str(item) {
Ok(val) => cur_degree = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse degree on line {lno} (`{item}`)",
),
});
}
},
1 => match usize::from_str(item) {
Ok(val) => cur_order = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse order on line {lno} (`{item}`)"
),
});
}
},
2 => match f64::from_str(&item.replace('D', "E")) {
Ok(val) => c_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse C_nm `{item}` on line {lno}"
),
});
}
},
3 => match f64::from_str(&item.replace('D', "E")) {
Ok(val) => s_nm = val,
Err(_) => {
return Err(NyxError::FileUnreadable {
msg: format!(
"Harmonics file:
could not parse S_nm `{item}` on line {lno}"
),
});
}
},
_ => break, // We aren't storing the covariance of these harmonics
}
}
if cur_degree > degree {
// The file is organized by degree, so once we've passed the maximum degree we want,
// we can safely stop reading the file.
break;
}
// Only insert this data into the hashmap if it's within the required order as well
if cur_order <= order {
c_nm_mat[(cur_degree, cur_order)] = c_nm;
s_nm_mat[(cur_degree, cur_order)] = s_nm;
}
// This serves as a warning.
max_order = if cur_order > max_order {
cur_order
} else {
max_order
};
max_degree = if cur_degree > max_degree {
cur_degree
} else {
max_degree
};
}
if max_degree < degree || max_order < order {
warn!(
"{filepath} only contained (degree, order) of ({max_degree}, {max_order}) instead of requested ({degree}, {order})",
);
} else {
info!("{filepath} loaded with (degree, order) = ({degree}, {order})");
}
Ok(HarmonicsMem {
order: max_order,
degree: max_degree,
c_nm: c_nm_mat,
s_nm: s_nm_mat,
})
}
/// Returns the maximum order of this gravity potential storage (Jnm=Jn2,Jn3...)
pub fn max_order_m(&self) -> usize {
self.order
}
/// Returns the maximum degree of this gravity potential storage (Jn=J2,J3...)
pub fn max_degree_n(&self) -> usize {
self.degree
}
/// Returns the C_nm and S_nm for the provided order and degree.
pub fn cs_nm(&self, degree: usize, order: usize) -> (f64, f64) {
(self.c_nm[(degree, order)], self.s_nm[(degree, order)])
}
}
#[test]
fn test_load_harmonic_files() {
HarmonicsMem::from_cof("data/JGM3.cof.gz", 50, 50, true).expect("could not load JGM3");
HarmonicsMem::from_egm("data/EGM2008_to2190_TideFree.gz", 120, 120, true)
.expect("could not load EGM2008");
HarmonicsMem::from_shadr("data/Luna_jggrx_1500e_sha.tab.gz", 1500, 1500, true)
.expect("could not load jggrx");
}