How do I install the Navigation Frames skill?

Run npx skillmds@latest add ashfordeou/navigation-frames in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Navigation Frames safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Navigation Frames?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Navigation Frames free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Navigation Frames?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Navigation Frames by ashfordeou — Agent Skill

Name: Navigation Frames
Author: ashfordeOU

Navigation Frames

Use when you must convert navigation coordinate frames for an aircraft or spacecraft: transform geodetic latitude, longitude, and altitude on the WGS-84 ellipsoid into ECEF position, build the ECEF to NED rotation matrix at a reference point, resolve velocity into north, east, and down components, and compute the Earth rotation angle from a Julian date for inertial to Earth-fixed frames. Produces ECEF coordinates in meters, the NED rotation matrix, NED velocity, and GMST rotation angle in radians. Trigger: navigation frames, ecef, ned, geodetic, wgs 84, earth rotation, coordinate conversion.

ashfordeOU 32b8909 3 files · 13.2 KB Updated Sep 17, 2026

File contents

Navigation Coordinate Frames (gnc-autonomy/navigation/navigation-frames)

Use when you need coordinate frame conversions for navigation: WGS-84 geodetic position to ECEF, the ECEF to NED rotation at a reference point, and the Earth rotation angle for inertial to Earth-fixed frames.

Domain quick reference

WGS-84 (World Geodetic System 1984) defines the reference ellipsoid with semi-major axis a = 6378137.0 m and flattening f = 1/298.257223563.
Geodetic coordinates (latitude, longitude, altitude) locate a point relative to the ellipsoid; ECEF is a Cartesian Earth-fixed frame with the Z axis along the spin axis toward the north pole.
NED is the local tangent-plane frame at a reference latitude and longitude: north, east, and down axes, with down positive.
The GMST Earth rotation angle relates inertial and Earth-fixed frames; it advances about 360.9856 degrees per mean solar day, and the Earth rotation rate is 7.2921159e-5 rad/s.
Units: meters, radians, days (UT1), m/s. Angles enter as radians; GMST is returned in radians in [0, 2*pi).

Workflow

Convert the geodetic position with geodetic_to_ecef(lat_rad, lon_rad, alt_m) to ECEF position in meters.
Build the frame rotation with ecef_to_ned(lat_ref_rad, lon_ref_rad) at the navigation reference point.
Transform the ECEF velocity with ned_velocity(vecef, r) into north, east, and down components in m/s.
For inertial to Earth-fixed alignment, compute gmst_rotation_angle(jd_ut1) from the Julian date (UT1), returned in radians mod 2*pi.

Pitfalls

Mixing degrees and radians: all angles are radians in the logic functions, so convert degrees with math.radians before calling.
Using the geodetic position as the reference point for the NED rotation instead of the navigation reference point.
Forgetting that altitude is height above the ellipsoid, not mean sea level, so geoid undulation can bias the result.
Confusing GMST with a full 360 degree day: the sidereal rotation is about 360.9856 degrees per day.
Reading NED signs loosely: down is positive, so a climbing vehicle has a negative vd component.

Behavior contract (gate 3)

The frame conversion logic is exercised by the gate 3 contract test: scripts/test_navigation_frames_logic.py against scripts/navigation_frames_logic.py (stdlib unittest, offline). Run: python3 skills/gnc-autonomy/navigation/navigation-frames/scripts/test_navigation_frames_logic.py

Compliance

The ECSS series (E-ST-10C, E-ST-40C, Q-ST-80C, M-ST-40C) covers space engineering and software; it is free to download and summarized and referenced only, per standards-map.yaml.
compliance: STANDARDS-REF, gated: false.

---name: navigation-framesdescription: Use when you must convert navigation coordinate frames for an aircraft or spacecraft: transform geodetic latitude, longitude, and altitude on the WGS-84 ellipsoid into ECEF position, build the ECEF to NED rotation matrix at a reference point, resolve velocity into north, east, and down components, and compute the Earth rotation angle from a Julian date for inertial to Earth-fixed frames. Produces ECEF coordinates in meters, the NED rotation matrix, NED velocity, and GMST rotation angle in radians. Trigger: navigation frames, ecef, ned, geodetic, wgs 84, earth rotation, coordinate conversion.license: Apache-2.0---# Navigation Coordinate Frames (gnc-autonomy/navigation/navigation-frames)Use when you need coordinate frame conversions for navigation: WGS-84geodetic position to ECEF, the ECEF to NED rotation at a referencepoint, and the Earth rotation angle for inertial to Earth-fixed frames.## Domain quick reference- WGS-84 (World Geodetic System 1984) defines the reference ellipsoid with semi-major axis a = 6378137.0 m and flattening f = 1/298.257223563.- Geodetic coordinates (latitude, longitude, altitude) locate a point relative to the ellipsoid; ECEF is a Cartesian Earth-fixed frame with the Z axis along the spin axis toward the north pole.- NED is the local tangent-plane frame at a reference latitude and longitude: north, east, and down axes, with down positive.- The GMST Earth rotation angle relates inertial and Earth-fixed frames; it advances about 360.9856 degrees per mean solar day, and the Earth rotation rate is 7.2921159e-5 rad/s.- Units: meters, radians, days (UT1), m/s. Angles enter as radians; GMST is returned in radians in [0, 2*pi).## Workflow1. Convert the geodetic position with geodetic_to_ecef(lat_rad, lon_rad, alt_m) to ECEF position in meters.2. Build the frame rotation with ecef_to_ned(lat_ref_rad, lon_ref_rad) at the navigation reference point.3. Transform the ECEF velocity with ned_velocity(vecef, r) into north, east, and down components in m/s.4. For inertial to Earth-fixed alignment, compute gmst_rotation_angle(jd_ut1) from the Julian date (UT1), returned in radians mod 2*pi.## Pitfalls- Mixing degrees and radians: all angles are radians in the logic functions, so convert degrees with math.radians before calling.- Using the geodetic position as the reference point for the NED rotation instead of the navigation reference point.- Forgetting that altitude is height above the ellipsoid, not mean sea level, so geoid undulation can bias the result.- Confusing GMST with a full 360 degree day: the sidereal rotation is about 360.9856 degrees per day.- Reading NED signs loosely: down is positive, so a climbing vehicle has a negative vd component.## Behavior contract (gate 3)The frame conversion logic is exercised by the gate 3 contract test:scripts/test_navigation_frames_logic.py againstscripts/navigation_frames_logic.py (stdlib unittest, offline).Run:python3 skills/gnc-autonomy/navigation/navigation-frames/scripts/test_navigation_frames_logic.py## Compliance- The ECSS series (E-ST-10C, E-ST-40C, Q-ST-80C, M-ST-40C) covers space engineering and software; it is free to download and summarized and referenced only, per standards-map.yaml.- compliance: STANDARDS-REF, gated: false.

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