sidereon_core/rinex_nav/
store.rs

1//! Broadcast-store selection and SPP source adapter.
2
3use crate::broadcast::{
4    satellite_state, satellite_state_cnav, satellite_state_cnav_unchecked,
5    satellite_state_unchecked, CnavRates, SatelliteState,
6};
7use crate::constants::{
8    BDS_EPOCH_MINUS_GPS_EPOCH_S, GPST_MINUS_BDT_S, GPS_EPOCH_TO_J2000_S, SECONDS_PER_WEEK,
9};
10use crate::error::{Error, Result as CoreResult};
11use crate::glonass;
12use crate::id::{GnssSatelliteId, GnssSystem};
13use crate::spp::EphemerisSource;
14
15use super::{
16    cnav_ura_nominal_m, is_beidou_geo, parse_glonass, parse_iono_corrections_checked,
17    parse_leap_seconds_checked, parse_nav, BroadcastGroupDelays, BroadcastIssue, BroadcastRecord,
18    CnavParameters, GlonassRecord, IonoCorrections, NavMessage, NavParseError, GLONASS_MAX_AGE_S,
19    MAX_EPHEMERIS_AGE_S,
20};
21
22/// Which navigation-message generation a store prefers when a GPS/QZSS
23/// satellite has both legacy and CNAV-family records.
24#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
25pub enum NavMessagePreference {
26    /// Prefer legacy records and use CNAV-family records only as fallback.
27    #[default]
28    PreferLegacy,
29    /// Prefer CNAV-family records and use legacy records as fallback.
30    PreferModern,
31}
32
33/// A queryable set of parsed broadcast records, usable as an SPP
34/// [`EphemerisSource`].
35///
36/// For a satellite and epoch it selects the record whose reference time `toe` is
37/// nearest in **continuous** GPS time (week number times the week length plus
38/// the seconds of week, not the seconds of week alone), and rejects the query as
39/// having no ephemeris if it falls outside that record's validity window - half
40/// the broadcast GPS curve-fit interval, or the coarse [`MAX_EPHEMERIS_AGE_S`]
41/// fallback for systems that do not broadcast one - so a stale or wrong-week
42/// product cannot silently produce a position.
43///
44/// [`from_nav`](BroadcastStore::from_nav) applies a default usability policy:
45/// healthy GPS LNAV, GPS/QZSS CNAV-family, Galileo I/NAV, BeiDou D1/D2, and
46/// GLONASS records are kept, with CNAV no-prediction URA records excluded.
47/// [`new`](BroadcastStore::new) keeps records verbatim for callers that want
48/// their own policy.
49pub struct BroadcastStore {
50    records: Vec<BroadcastRecord>,
51    glonass: Vec<GlonassRecord>,
52    leap_seconds: Option<f64>,
53    iono: IonoCorrections,
54    message_preference: NavMessagePreference,
55}
56
57impl BroadcastStore {
58    /// Build a store from already-parsed Keplerian records, verbatim (no policy
59    /// filter, no GLONASS records, no leap-second offset, and no ionosphere
60    /// coefficients; use [`from_nav`](Self::from_nav) to capture those).
61    pub fn new(records: Vec<BroadcastRecord>) -> CoreResult<Self> {
62        for record in &records {
63            validate_manual_record(record)?;
64        }
65        Ok(Self {
66            records,
67            glonass: Vec::new(),
68            leap_seconds: None,
69            iono: IonoCorrections::default(),
70            message_preference: NavMessagePreference::default(),
71        })
72    }
73
74    /// Parse a RINEX 3.x/4.xx navigation file and keep the records usable for
75    /// single-frequency positioning under the default policy: healthy GPS LNAV,
76    /// GPS/QZSS CNAV-family records with URA prediction, Galileo I/NAV, BeiDou
77    /// D1/D2, and GLONASS. The header's broadcast ionosphere coefficients (see
78    /// [`iono_corrections`](Self::iono_corrections)) and leap-second offset are
79    /// captured.
80    pub fn from_nav(text: &str) -> Result<Self, NavParseError> {
81        let records = parse_nav(text)?
82            .into_iter()
83            .filter(Self::is_default_usable)
84            .collect();
85        let glonass = parse_glonass(text)?
86            .into_iter()
87            .filter(|r| r.sv_health == 0.0)
88            .collect();
89        Ok(Self {
90            records,
91            glonass,
92            leap_seconds: parse_leap_seconds_checked(text)?,
93            iono: parse_iono_corrections_checked(text)?,
94            message_preference: NavMessagePreference::default(),
95        })
96    }
97
98    /// Set the GPS/QZSS legacy-vs-CNAV selection preference.
99    pub fn set_message_preference(&mut self, preference: NavMessagePreference) {
100        self.message_preference = preference;
101    }
102
103    /// The GPS/QZSS legacy-vs-CNAV selection preference.
104    pub const fn message_preference(&self) -> NavMessagePreference {
105        self.message_preference
106    }
107
108    /// The broadcast ionosphere coefficients parsed from the navigation header
109    /// or RINEX 4 body `> ION` frames (GPS `GPSA`/`GPSB`, BeiDou `BDSA`/`BDSB`,
110    /// and Galileo `GAL`). Empty for a store built with [`new`](Self::new).
111    pub fn iono_corrections(&self) -> IonoCorrections {
112        self.iono
113    }
114
115    /// The held GLONASS records.
116    pub fn glonass_records(&self) -> &[GlonassRecord] {
117        &self.glonass
118    }
119
120    /// The GLONASS FDMA frequency channels carried by the held broadcast
121    /// records, keyed by satellite PRN/slot (`[-7, 6]`).
122    ///
123    /// Lets a consumer source the per-satellite channel numbers - needed to
124    /// scale the GLONASS ionospheric delay per carrier - from the broadcast
125    /// navigation message when an observation file carries no `GLONASS SLOT /
126    /// FRQ #` header records. Each GLONASS satellite broadcasts one channel, so
127    /// the map has at most one entry per slot. The result keys/values match the
128    /// `glonass_slots` layout of [`crate::rinex_obs::ObsHeader`], so a consumer
129    /// can use this map directly where an OBS file would otherwise supply one.
130    pub fn glonass_frequency_channels(&self) -> std::collections::BTreeMap<u8, i8> {
131        self.glonass
132            .iter()
133            .map(|r| (r.satellite_id.prn, r.freq_channel as i8))
134            .collect()
135    }
136
137    /// The default usability policy: healthy and single-frequency-appropriate
138    /// messages. CNAV-family records with no URA prediction are excluded.
139    fn is_default_usable(r: &BroadcastRecord) -> bool {
140        r.sv_health == 0.0
141            && matches!(
142                r.message,
143                NavMessage::GpsLnav
144                    | NavMessage::GpsCnav
145                    | NavMessage::GpsCnav2
146                    | NavMessage::QzssCnav
147                    | NavMessage::QzssCnav2
148                    | NavMessage::GalileoInav
149                    | NavMessage::BeidouD1
150                    | NavMessage::BeidouD2
151            )
152            && (!r.message.is_cnav_family()
153                || r.cnav
154                    .map(|cnav| cnav_ura_nominal_m(cnav.ura_ed_index).is_some())
155                    .unwrap_or(false))
156    }
157
158    /// The held records.
159    pub fn records(&self) -> &[BroadcastRecord] {
160        &self.records
161    }
162
163    /// Select the valid record for `sat` with a matching GPS issue byte at `t`.
164    pub fn select_by_iode_at(
165        &self,
166        sat: GnssSatelliteId,
167        iode: u8,
168        t_j2000_s: f64,
169    ) -> Option<&BroadcastRecord> {
170        let (t_continuous, _) = query_continuous_time(sat, t_j2000_s)?;
171        self.records
172            .iter()
173            .filter(|r| r.satellite_id == sat)
174            .filter(|r| r.issue_of_data.message == NavMessage::GpsLnav)
175            .filter(|r| r.issue_of_data.issue == u32::from(iode))
176            .filter(|r| (t_continuous - Self::toe_continuous_s(r)).abs() <= Self::half_window_s(r))
177            .min_by(|a, b| {
178                let da = (t_continuous - Self::toe_continuous_s(a)).abs();
179                let db = (t_continuous - Self::toe_continuous_s(b)).abs();
180                da.partial_cmp(&db).unwrap_or(core::cmp::Ordering::Equal)
181            })
182    }
183
184    /// Evaluate a matching issue-specific broadcast record at `t`.
185    pub fn state_by_iode_at(
186        &self,
187        sat: GnssSatelliteId,
188        iode: u8,
189        t_j2000_s: f64,
190    ) -> Option<([f64; 3], f64)> {
191        let (t_continuous, is_geo) = query_continuous_time(sat, t_j2000_s)?;
192        let rec = self.select_by_iode_at(sat, iode, t_j2000_s)?;
193        let sow = t_continuous.rem_euclid(SECONDS_PER_WEEK);
194        let state = evaluate_record_unchecked(rec, sow, is_geo);
195        let position = state.orbit.position().ok()?;
196        Some((position.as_array(), state.clock.dt_clock_total_s))
197    }
198
199    /// Keep only the records matching a predicate (e.g. a custom message/health
200    /// policy on a store built with [`new`](BroadcastStore::new)).
201    pub fn retain(&mut self, keep: impl FnMut(&BroadcastRecord) -> bool) {
202        self.records.retain(keep);
203    }
204
205    /// Continuous native broadcast time of a record's `toe`
206    /// (`week * 604800 + tow` in the record's own scale).
207    fn toe_continuous_s(rec: &BroadcastRecord) -> f64 {
208        f64::from(rec.toe.week) * SECONDS_PER_WEEK + rec.toe.tow_s
209    }
210
211    /// The half-validity window (seconds either side of `toe`) for a record: half
212    /// the broadcast GPS fit interval, or [`MAX_EPHEMERIS_AGE_S`] when no fit
213    /// interval is broadcast (Galileo, BeiDou).
214    fn half_window_s(rec: &BroadcastRecord) -> f64 {
215        match rec.fit_interval_s {
216            Some(fit) => fit / 2.0,
217            None => MAX_EPHEMERIS_AGE_S,
218        }
219    }
220
221    /// The record for `sat` whose native-system `toe` is nearest
222    /// `t_continuous_s` **among those whose validity window covers the
223    /// query** (see [`half_window_s`](Self::half_window_s)). Filtering by
224    /// validity before choosing the nearest means a query just past one record's
225    /// fit interval can still be served by a farther record whose own window is
226    /// wide enough, rather than being rejected outright.
227    fn select(&self, sat: GnssSatelliteId, t_continuous_s: f64) -> Option<&BroadcastRecord> {
228        let mut preferred = None;
229        let mut fallback = None;
230        for record in self.records.iter().filter(|r| r.satellite_id == sat) {
231            if (t_continuous_s - Self::toe_continuous_s(record)).abs() > Self::half_window_s(record)
232            {
233                continue;
234            }
235            if self.is_preferred_family(record) {
236                select_better_candidate(&mut preferred, record, t_continuous_s);
237            } else {
238                select_better_candidate(&mut fallback, record, t_continuous_s);
239            }
240        }
241        preferred.or(fallback)
242    }
243
244    fn is_preferred_family(&self, record: &BroadcastRecord) -> bool {
245        if !matches!(
246            record.satellite_id.system,
247            GnssSystem::Gps | GnssSystem::Qzss
248        ) {
249            return true;
250        }
251        match self.message_preference {
252            NavMessagePreference::PreferLegacy => !record.message.is_cnav_family(),
253            NavMessagePreference::PreferModern => record.message.is_cnav_family(),
254        }
255    }
256
257    /// Select the broadcast record matching a specific issue and message at the
258    /// query epoch.
259    pub fn select_by_issue_at(
260        &self,
261        sat: GnssSatelliteId,
262        issue: BroadcastIssue,
263        nav_message: NavMessage,
264        t_j2000_s: f64,
265    ) -> Option<&BroadcastRecord> {
266        if issue.message != nav_message {
267            return None;
268        }
269        let (t_continuous_s, _) = query_continuous_time(sat, t_j2000_s)?;
270        self.records
271            .iter()
272            .filter(|r| {
273                r.satellite_id == sat
274                    && r.message == nav_message
275                    && r.issue_of_data == issue
276                    && (t_continuous_s - Self::toe_continuous_s(r)).abs() <= Self::half_window_s(r)
277            })
278            .min_by(|a, b| {
279                let da = (t_continuous_s - Self::toe_continuous_s(a)).abs();
280                let db = (t_continuous_s - Self::toe_continuous_s(b)).abs();
281                da.partial_cmp(&db).unwrap_or(core::cmp::Ordering::Equal)
282            })
283    }
284
285    /// The GLONASS record for `sat` nearest the GPST-aligned query `t_j2000_s`
286    /// (within [`GLONASS_MAX_AGE_S`]), with `tk` = query − the record's reference
287    /// epoch in GPS time. Returns `None` if no leap-second offset was parsed (the
288    /// GLONASS UTC epoch then cannot be placed on the GPST timeline).
289    fn select_glonass(
290        &self,
291        sat: GnssSatelliteId,
292        t_j2000_s: f64,
293    ) -> Option<(&GlonassRecord, f64)> {
294        let leap = self.leap_seconds?;
295        let toe_gpst = |r: &GlonassRecord| r.toe_utc_j2000_s + leap;
296        let rec = self
297            .glonass
298            .iter()
299            .filter(|r| r.satellite_id == sat)
300            .min_by(|a, b| {
301                let da = (t_j2000_s - toe_gpst(a)).abs();
302                let db = (t_j2000_s - toe_gpst(b)).abs();
303                da.partial_cmp(&db).unwrap_or(core::cmp::Ordering::Equal)
304            })?;
305        let tk = t_j2000_s - toe_gpst(rec);
306        if tk.abs() <= GLONASS_MAX_AGE_S {
307            Some((rec, tk))
308        } else {
309            None
310        }
311    }
312}
313
314fn validate_manual_record(record: &BroadcastRecord) -> CoreResult<()> {
315    validate_finite(record.toe.tow_s, "record.toe.tow_s")?;
316    validate_finite(record.toc.tow_s, "record.toc.tow_s")?;
317    validate_finite(record.sv_health, "record.sv_health")?;
318    validate_finite(record.sv_accuracy_m, "record.sv_accuracy_m")?;
319    if let Some(fit) = record.fit_interval_s {
320        validate_finite(fit, "record.fit_interval_s")?;
321        if fit <= 0.0 {
322            return Err(invalid_input("record.fit_interval_s", "not positive"));
323        }
324    }
325    validate_group_delays(record.group_delays)?;
326    validate_cnav_presence(record)?;
327    if let Some(cnav) = record.cnav {
328        validate_cnav_parameters(cnav)?;
329    }
330
331    if let Some(cnav) = record.cnav {
332        satellite_state_cnav(
333            &record.elements,
334            &cnav_rates(cnav),
335            &record.clock,
336            &record.constants(),
337            record.elements.toe_sow,
338            record.broadcast_clock_group_delay_s(),
339        )
340        .map(|_| ())
341    } else {
342        satellite_state(
343            &record.elements,
344            &record.clock,
345            &record.constants(),
346            record.elements.toe_sow,
347            record.broadcast_clock_group_delay_s(),
348            is_beidou_geo(record.satellite_id),
349        )
350        .map(|_| ())
351    }
352}
353
354fn validate_group_delays(delays: BroadcastGroupDelays) -> CoreResult<()> {
355    for (field, value) in [
356        ("group_delays.gps_tgd_s", delays.gps_tgd_s),
357        (
358            "group_delays.galileo_bgd_e5a_e1_s",
359            delays.galileo_bgd_e5a_e1_s,
360        ),
361        (
362            "group_delays.galileo_bgd_e5b_e1_s",
363            delays.galileo_bgd_e5b_e1_s,
364        ),
365        ("group_delays.beidou_tgd1_s", delays.beidou_tgd1_s),
366        ("group_delays.beidou_tgd2_s", delays.beidou_tgd2_s),
367        ("group_delays.cnav_isc_l1ca_s", delays.cnav_isc_l1ca_s),
368        ("group_delays.cnav_isc_l2c_s", delays.cnav_isc_l2c_s),
369        ("group_delays.cnav_isc_l5i5_s", delays.cnav_isc_l5i5_s),
370        ("group_delays.cnav_isc_l5q5_s", delays.cnav_isc_l5q5_s),
371        ("group_delays.cnav_isc_l1cd_s", delays.cnav_isc_l1cd_s),
372        ("group_delays.cnav_isc_l1cp_s", delays.cnav_isc_l1cp_s),
373    ] {
374        if let Some(value) = value {
375            validate_finite(value, field)?;
376        }
377    }
378    Ok(())
379}
380
381fn validate_cnav_presence(record: &BroadcastRecord) -> CoreResult<()> {
382    if record.message.is_cnav_family() != record.cnav.is_some() {
383        return Err(invalid_input(
384            "record.cnav",
385            "must be present only for CNAV-family messages",
386        ));
387    }
388    Ok(())
389}
390
391fn validate_cnav_parameters(params: CnavParameters) -> CoreResult<()> {
392    validate_finite(params.adot_m_s, "record.cnav.adot_m_s")?;
393    validate_finite(
394        params.delta_n0_dot_rad_s2,
395        "record.cnav.delta_n0_dot_rad_s2",
396    )?;
397    validate_finite(params.top.tow_s, "record.cnav.top.tow_s")?;
398    validate_finite(
399        params.transmission_time_sow,
400        "record.cnav.transmission_time_sow",
401    )?;
402    if !(-16..=15).contains(&params.ura_ed_index) {
403        return Err(invalid_input("record.cnav.ura_ed_index", "out of range"));
404    }
405    if !(-16..=15).contains(&params.ura_ned0_index) {
406        return Err(invalid_input("record.cnav.ura_ned0_index", "out of range"));
407    }
408    if params.ura_ned1_index > 7 {
409        return Err(invalid_input("record.cnav.ura_ned1_index", "out of range"));
410    }
411    if params.ura_ned2_index > 7 {
412        return Err(invalid_input("record.cnav.ura_ned2_index", "out of range"));
413    }
414    Ok(())
415}
416
417fn cnav_rates(params: CnavParameters) -> CnavRates {
418    CnavRates {
419        adot_m_s: params.adot_m_s,
420        delta_n0_dot_rad_s2: params.delta_n0_dot_rad_s2,
421    }
422}
423
424fn evaluate_record_unchecked(rec: &BroadcastRecord, sow: f64, is_geo: bool) -> SatelliteState {
425    if let Some(cnav) = rec.cnav {
426        satellite_state_cnav_unchecked(
427            &rec.elements,
428            &cnav_rates(cnav),
429            &rec.clock,
430            &rec.constants(),
431            sow,
432            rec.broadcast_clock_group_delay_s(),
433        )
434    } else {
435        satellite_state_unchecked(
436            &rec.elements,
437            &rec.clock,
438            &rec.constants(),
439            sow,
440            rec.broadcast_clock_group_delay_s(),
441            is_geo,
442        )
443    }
444}
445
446fn select_better_candidate<'a>(
447    best: &mut Option<&'a BroadcastRecord>,
448    candidate: &'a BroadcastRecord,
449    t_continuous_s: f64,
450) {
451    let Some(current) = *best else {
452        *best = Some(candidate);
453        return;
454    };
455    if candidate_is_better(candidate, current, t_continuous_s) {
456        *best = Some(candidate);
457    }
458}
459
460fn candidate_is_better(
461    candidate: &BroadcastRecord,
462    current: &BroadcastRecord,
463    t_continuous_s: f64,
464) -> bool {
465    let da = (t_continuous_s - BroadcastStore::toe_continuous_s(candidate)).abs();
466    let db = (t_continuous_s - BroadcastStore::toe_continuous_s(current)).abs();
467    match da.partial_cmp(&db).unwrap_or(core::cmp::Ordering::Equal) {
468        core::cmp::Ordering::Less => true,
469        core::cmp::Ordering::Greater => false,
470        core::cmp::Ordering::Equal => {
471            cnav_tie_rank(candidate.message) < cnav_tie_rank(current.message)
472        }
473    }
474}
475
476const fn cnav_tie_rank(message: NavMessage) -> u8 {
477    match message {
478        NavMessage::GpsCnav | NavMessage::QzssCnav => 0,
479        NavMessage::GpsCnav2 | NavMessage::QzssCnav2 => 1,
480        _ => 0,
481    }
482}
483
484fn validate_finite(value: f64, field: &'static str) -> CoreResult<()> {
485    if value.is_finite() {
486        Ok(())
487    } else {
488        Err(invalid_input(field, "not finite"))
489    }
490}
491
492fn invalid_input(field: &'static str, reason: &'static str) -> Error {
493    Error::InvalidInput(format!("{field} {reason}"))
494}
495
496impl core::str::FromStr for BroadcastStore {
497    type Err = NavParseError;
498
499    fn from_str(s: &str) -> Result<Self, Self::Err> {
500        Self::from_nav(s)
501    }
502}
503
504impl EphemerisSource for BroadcastStore {
505    fn position_clock_at_j2000_s(
506        &self,
507        sat: GnssSatelliteId,
508        t_j2000_s: f64,
509    ) -> Option<([f64; 3], f64)> {
510        // GLONASS is not Keplerian: integrate its broadcast state vector with the
511        // RK4 propagator. Its reference epoch is UTC, mapped onto the GPST-aligned
512        // query via the parsed leap-second offset.
513        if sat.system == GnssSystem::Glonass {
514            let (rec, tk) = self.select_glonass(sat, t_j2000_s)?;
515            let state0 = [
516                rec.pos_m[0],
517                rec.pos_m[1],
518                rec.pos_m[2],
519                rec.vel_m_s[0],
520                rec.vel_m_s[1],
521                rec.vel_m_s[2],
522            ];
523            let state = glonass::propagate(state0, rec.acc_m_s2, tk).ok()?;
524            let clock = glonass::clock_offset_s(rec.clk_bias, rec.gamma_n, tk);
525            return Some(([state[0], state[1], state[2]], clock));
526        }
527
528        // Supported Keplerian systems only; a record from any other system (for
529        // example SBAS or NavIC) reports no ephemeris rather than being evaluated
530        // with the wrong model. (`from_nav` already restricts records, but `new`
531        // accepts arbitrary ones.)
532        // Map the receive instant (J2000, GPST-aligned) onto the satellite
533        // system's continuous time and seconds of week. BeiDou runs on BDT
534        // (= GPST - 14 s) with its week epoch 1356 weeks after the GPS epoch, and
535        // its geostationary satellites take the GEO orbit branch.
536        // `query_continuous_time` returns None for non-Keplerian systems.
537        let (t_continuous, is_geo) = query_continuous_time(sat, t_j2000_s)?;
538
539        let rec = self.select(sat, t_continuous)?;
540        let sow = t_continuous.rem_euclid(SECONDS_PER_WEEK);
541        let state = evaluate_record_unchecked(rec, sow, is_geo);
542        let position = state.orbit.position().ok()?;
543        Some((position.as_array(), state.clock.dt_clock_total_s))
544    }
545}
546
547fn query_continuous_time(sat: GnssSatelliteId, t_j2000_s: f64) -> Option<(f64, bool)> {
548    if !matches!(
549        sat.system,
550        GnssSystem::Gps | GnssSystem::Galileo | GnssSystem::BeiDou | GnssSystem::Qzss
551    ) {
552        return None;
553    }
554    let gpst_continuous = t_j2000_s + GPS_EPOCH_TO_J2000_S;
555    if sat.system == GnssSystem::BeiDou {
556        Some((
557            gpst_continuous - GPST_MINUS_BDT_S - BDS_EPOCH_MINUS_GPS_EPOCH_S,
558            is_beidou_geo(sat),
559        ))
560    } else {
561        Some((gpst_continuous, false))
562    }
563}
sidereon_core/rinex_nav/store.rs

sidereon_core/rinex_nav/
store.rs
