NAV absolute time (#337)

* NAV (V2, V3, V4) time offset support upgrade
* Time offset parsing & formatting

---------

Signed-off-by: Guillaume W. Bres <[email protected]>

Author: gwbres

README.md

@@ -23,8 +23,16 @@ To contribute to either of our project or join our community, you way
 - All modern GNSS constellations, codes and signals
   - Surveying with GPS, Galileo, BeiDou and QZSS
 - Time scales: GPST, QZSST, BDT, GST, UTC, TAI
-- RINEX V4 full support
 - Efficient seamless compression and decompression
+- RINEX V4 full support, including
+  - new Ionospheric coorections
+  - new Time offset corrections
+  - precise Earth Orientation updates
+- Navigation supported in the following constellations
+  - GPS
+  - Galileo
+  - BeiDou
+  - QZSS
 - Most RINEX formats supported (see following table)
 - High Precision Clock RINEX products (for PPP)
 - DORIS (special RINEX)
@@ -33,7 +41,7 @@ To contribute to either of our project or join our community, you way
 
 ## Warnings :warning:
 
-- Navigation is currently not feasible with Glonass and IRNSS
+- Navigation is currently not feasible with Glonass, SBAS and IRNSS
 - File production might lack some features, mostly because we're currently focused on data processing
 
 ## Citation and referencing

src/error.rs

@@ -124,8 +124,14 @@ pub enum ParsingError {
     IonexGridCoordinates,
     #[error("nav: invalid frame class")]
     NavFrameClass,
+    #[error("nav: invalid timescale")]
+    NavInvalidTimescale,
     #[error("nav: invalid message type")]
     NavMsgType,
+    #[error("nav: (ref) epoch week counter parsing")]
+    NavEpochWeekCounter,
+    #[error("nav: time offset parsing")]
+    NavTimeOffsetParinsg,
     #[error("nav: unknown radio message")]
     NoNavigationDefinition,
     #[error("nav: invalid health flag definition")]