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排查页面顺序问题时顺带审计发现: OMM/CSV 历元在子夜后约 86 秒内会被解析成
完全错误的值, 且不抛异常 —— 静默的错误数据。
## 根因
DataParser.parseCSV 用字符串拼接构造历元:
val frac = ((hour + min + sec + ms) / 86400000.0).toString().substring(1)
val epoch = "${year.substring(2)}$day$frac".toDouble()
substring(1) 的意图是切掉 "0.123" 的前导 0。但 Double.toString() 在数值
小于 1e-3 时切换为科学计数法, 于是被切掉的是【有效数字】, 剩下的指数后缀
让整个字符串重新变成一个合法但语义完全错误的 double。
Kotlin 侧实测(单测失败信息):
00:00:01.000 期望 25001.000011574073 实得 0.2500115740740741
00:01:00.000 期望 25001.000694444443 实得 2.5001944444444444
与 JDK 侧独立验证逐位一致。00:01:26.4 之后 frac >= 0.001, 不再用科学计数法,
所以这个 bug 只在每天前 86.4 秒的历元上出现(约占 0.1%), Celestrak OMM 数据
里整分历元并不罕见。
## 影响
runCatching 抓不到(没有异常), 该卫星的 juliandDateOfEpoch 会推出 year=2000
day≈0, tsince 偏差约 26 年 —— 方位/仰角/过境预报彻底失效, 不是精度下降。
且用户无从察觉。
## 修复
改为数值相加, 不经过字符串:
val dayFraction = (hour + min + sec + ms) / 86400000.0
val epoch = "${year.substring(2)}$day".toDouble() + dayFraction
"25001".toDouble() + 0.0000115 = 25001.0000115, 无科学计数法风险。
## 验证
DataParserTest 新增 5 个历元回归测试(子夜整点/子夜后 1 秒/子夜后 1 分钟/
正午/当日最后一毫秒)。先确认前两个在旧实现下失败(failures=2), 修复后:
- DataParserTest 24 个测试全绿(原有 19 个无回归)
- :core:domain:test 全量 105 个测试 0 失败 0 错误
Look4Sat: Satellite tracker
Radio satellite tracker and pass predictor for Android, inspired by Gpredict
Track satellite passes with ease!
Thanks to Celestrak and SatNOGS you have access to over 9000 active satellites.
You can search the entire database by NORAD Catalog Number or the satellite's name.
Orbital positions and passes are calculated relative to your location.
To get reliable data make sure to set the station position via the app Settings.
The application is built using Kotlin, Coroutines, Jetpack Compose and Navigation.
It is now and always will be completely ad-free and open-source.
Main features:
- Predicting satellite positions and passes for up to 10 days
- Showing the list of currently active and upcoming satellite passes
- Showing the active pass progress, polar trajectory and transceivers info
- Showing the satellite positional data, footprint and ground track on the map
- Custom TLE satellite data import is available via Three Line Element .txt files
- Offline first: calculations are made offline. Weekly TLE data update is recommended.
License
The Look4Sat application code is licensed under the GNU General Public License v3.0.
The CW decoder in feature/cw bundles the DeepCW
neural decoding model, licensed under the GNU Affero General Public License v3.0 only
(AGPL-3.0-only). Because the combined work incorporates an AGPL-3.0 component, the
combined work is distributed under the
GNU Affero General Public License v3.0 — GPL-3.0 Section 13 permits the
combination, and AGPL-3.0 Section 13 applies to the combined work as a whole.
Model provenance and attribution are documented in
feature/cw/licenses/NOTICE.md; the original GPL-3.0
text is preserved at feature/cw/licenses/Look4Sat-GPL-3.0.txt. The CW model runs
locally on-device and does not provide services over a network.