This video will change everything in how you prepare for your next long sail. I’m showing you the exact ‘Master Prompt’ I use to calculate Compass Deviation and Magnetic Variation in seconds, and even converting coordinates into degrees, minutes and seconds in the same go. Whether you’re crossing the Atlantic or island hopping in Southeast Asia, this is the ultimate navigation hack to keep you on course when the screens go dark. Navigating without GPS is not that difficult, but you need to be prepared. And I will show you how to in this free video. Download the open-source prompt below!
If you’re a cruiser—or planning to be—Subscribe to follow my journey and grab my free AI navigation prompts to keep your passage planning sharp, no matter where in the world you’re sailing. Fair winds from the tropics!
Copy from here:
Role: Master Navigator
Task: Generate a theoretical Rhumb Line navigation backup plan based on the provided GPX data.
1. Universal Waypoint Processing:
Identify all entries in the provided GPX file.
Assign a sequential Waypoint Number (WP 1, WP 2, etc.) to every point found.
Data Integrity: Process every point in the sequence provided. Do not omit, truncate, or summarise any portion of the route. Every waypoint must have its own row.
2. Midpoint Logic:
Calculate the distance between every sequential pair (WP n to WP n+1).
If the distance between two points exceeds 100nm, insert a new row for the exact midpoint coordinates. Label this row ‘WP [Number] MID’.
Calculate the True Bearing and WMM 2025 Declination for these midpoints.
3. Navigational Calculations:
Coordinates: Convert decimal degrees to Degrees, Minutes, Seconds (DMS).
Dist: Nautical Miles (nm) to the next point.
True Brg: Precise Rhumb Line bearing to the next point.
Decl (2025): Use the latest World Magnetic Model for the specific coordinate.
Mag C: True Bearing corrected for Declination (Variation).
Dev (Variable): Apply deviation based on a simulated deviation card:
For headings 000°–090°: Apply +2°
For headings 091°–180°: Apply +1°
For headings 181°–270°: Apply -1°
For headings 271°–359°: Apply -2°
Comp C: Magnetic Course corrected for Deviation.
4. ETAs: Create 4 separate columns for 4, 5, 6, and 7 knots (showing cumulative travel time from the start).
5. Output Format:
Table Label: “Master Navigation Table”
Columns: [WP #] | [Dist Next] | [Coordinates DMS] | [True Brg] | [Decl (2025)] | [Mag C] | [Dev] | [Comp C] | [ETA 4kt] | [ETA 5kt] | [ETA 6kt] | [ETA 7kt]
CSV Section: Provide a raw, comma-separated code block (CSV) at the end containing all rows (Waypoints + Midpoints) that matches the table exactly for import into Excel or Numbers.
“CRITICAL: This is for a professional maritime document. You are prohibited from using ‘…’ or skipping any rows. If the output is too long for one message, stop at WP 15 and I will say ‘Continue’ for the rest.” GPX File Input:
[PASTE YOUR GPX DATA HERE]
The prompt above is free to use, but make sure to check your data, and also please remember navigation is always done at your own risk.
Thank you so much for tagging along and for the patrons’ support in making this video possible.
Patreon: https://www.patreon.com/Sailingwiththomas
You can even tip me https://paypal.me/SailingwithThomas
If you enjoyed some of the soundtracks in this episode, a full version is found here @SwTMusicOnly
Please also check out my practical channel @PracticalThomas
THANK YOU SO MUCH FOR WATCHING AND SUBSCRIBING!
You can also follow sailing with Thomas on other platforms for almost daily updated pics and videos, and even find yourself a new T-Shirt:
Facebook: https://www.facebook.com/sailingwiththomas
Instagram: https://www.instagram.com/sailingwiththomas
Shop: https://sailingwiththomascom.wpcomstaging.com/shop/
ABOUT THIS CHANNEL:
I’m a sailor with a YouTube channel and not a YouTuber. Sailing around the world in a Bavaria 55 Cruiser, mostly solo, making videos whenever we have time for it.
Comfortable at sea with 4 decades of sailing experience and hundreds of thousands of miles behind me.
Even though this is season 8 on YouTube, I did not make that many videos in the beginning, and obviously not from my entire sailing life. Before full-time sailing 7 years ago, I sailed several seasons in the Mediterranean, and obviously also in Scandinavia. I had my first sailboat at age 7 and have been sailing and racing ever since. I also have more than 10 years of experience as a captain in search and rescue at sea in Norway.
This video will change everything in how you prepare for your next long sail. I’m showing you the exact 'Master Prompt' I use to calculate Compass Deviation and Magnetic Variation in seconds, and even converting coordinates into degrees, minutes and seconds in the same go. Whether you're crossing the Atlantic or island hopping in Southeast Asia, this is the ultimate navigation hack to keep you on course when the screens go dark. Navigating without GPS is not that difficult, but you need to be prepared. And I will show you how to in this free video. Download the open-source prompt below!
If you’re a cruiser—or planning to be—Subscribe to follow my journey and grab my free AI navigation prompts to keep your passage planning sharp, no matter where in the world you're sailing. Fair winds from the tropics!
Copy from here:
Role: Master Navigator
Task: Generate a theoretical Rhumb Line navigation backup plan based on the provided GPX data.
1. Universal Waypoint Processing:
Identify all entries in the provided GPX file.
Assign a sequential Waypoint Number (WP 1, WP 2, etc.) to every point found.
Data Integrity: Process every point in the sequence provided. Do not omit, truncate, or summarise any portion of the route. Every waypoint must have its own row.
2. Midpoint Logic:
Calculate the distance between every sequential pair (WP n to WP n+1).
If the distance between two points exceeds 100nm, insert a new row for the exact midpoint coordinates. Label this row 'WP [Number] MID'.
Calculate the True Bearing and WMM 2025 Declination for these midpoints.
3. Navigational Calculations:
Coordinates: Convert decimal degrees to Degrees, Minutes, Seconds (DMS).
Dist: Nautical Miles (nm) to the next point.
True Brg: Precise Rhumb Line bearing to the next point.
Decl (2025): Use the latest World Magnetic Model for the specific coordinate.
Mag C: True Bearing corrected for Declination (Variation).
Dev (Variable): Apply deviation based on a simulated deviation card:
For headings 000°–090°: Apply +2°
For headings 091°–180°: Apply +1°
For headings 181°–270°: Apply -1°
For headings 271°–359°: Apply -2°
Comp C: Magnetic Course corrected for Deviation.
4. ETAs: Create 4 separate columns for 4, 5, 6, and 7 knots (showing cumulative travel time from the start).
5. Output Format:
Table Label: "Master Navigation Table"
Columns: [WP #] | [Dist Next] | [Coordinates DMS] | [True Brg] | [Decl (2025)] | [Mag C] | [Dev] | [Comp C] | [ETA 4kt] | [ETA 5kt] | [ETA 6kt] | [ETA 7kt]
CSV Section: Provide a raw, comma-separated code block (CSV) at the end containing all rows (Waypoints + Midpoints) that matches the table exactly for import into Excel or Numbers.
"CRITICAL: This is for a professional maritime document. You are prohibited from using '...' or skipping any rows. If the output is too long for one message, stop at WP 15 and I will say 'Continue' for the rest." GPX File Input:
[PASTE YOUR GPX DATA HERE]
The prompt above is free to use, but make sure to check your data, and also please remember navigation is always done at your own risk.
Thank you so much for tagging along and for the patrons' support in making this video possible.
Patreon: https://www.patreon.com/Sailingwiththomas
You can even tip me https://paypal.me/SailingwithThomas
If you enjoyed some of the soundtracks in this episode, a full version is found here @SwTMusicOnly
Please also check out my practical channel @PracticalThomas
THANK YOU SO MUCH FOR WATCHING AND SUBSCRIBING!
You can also follow sailing with Thomas on other platforms for almost daily updated pics and videos, and even find yourself a new T-Shirt:
Facebook: https://www.facebook.com/sailingwiththomas
Instagram: https://www.instagram.com/sailingwiththomas
Shop: https://sailingwiththomascom.wpcomstaging.com/shop/
ABOUT THIS CHANNEL:
I'm a sailor with a YouTube channel and not a YouTuber. Sailing around the world in a Bavaria 55 Cruiser, mostly solo, making videos whenever we have time for it.
Comfortable at sea with 4 decades of sailing experience and hundreds of thousands of miles behind me.
Even though this is season 8 on YouTube, I did not make that many videos in the beginning, and obviously not from my entire sailing life. Before full-time sailing 7 years ago, I sailed several seasons in the Mediterranean, and obviously also in Scandinavia. I had my first sailboat at age 7 and have been sailing and racing ever since. I also have more than 10 years of experience as a captain in search and rescue at sea in Norway.
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