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Navigation Telecommunications

RTL-SDR for Marine HF Weather Fax

Introduction Up to date weather information is critical for sailors and can make the difference between a safe or a hazardous passage. Marine HF Weather Fax has been working reliably for many years and is an independent source of valuable information. NOAA’s Marine Weather Fax page (Ref.1) has all the information you need to use […]

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Navigation

Celestial Navigation Basics – Fix

In this post we will look at how to generate a fix from observations of two Celestial Bodies. In previous posts we looked at Hc (Ref.9), Ho (Ref.8), Ha (Ref.7) and Hs (Ref.6). Now we are in a position to use Ho & Hc from two measurements to get our fix. The Marcq St. Hilaire […]

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Navigation

Celestial Navigation Basics – Early Morning Sky

This morning I couldn’t sleep. I went out to the balcony and looked up. It was beautiful, the partially occluded Moon & Venus were perfectly visible. I checked the NavPac Identification of Stars & Planets, and there they were sitting next to one another at Az_moon=86deg & Az_venus=88deg. Download “Celestial Navigation Basics & Equipment” References […]

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Navigation

RTL-SDR for AIS

Introduction AIS Automatic Identification System for Ships is a traffic system that uses VHF transponders on vessels to periodically send out location information. It was developed by Swedish inventor Hakan Lans and is similar in concept to the ADS-B transponder system used on aircraft for position reporting. AIS uses two VHF marine channels 87B (161.975 MHz) […]

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Navigation

Celestial Navigation Basics – Hc Calculated Altitude

In this post we will look at how to determine Hc the calculated altitude and compare this to Ho the observed altitude. The difference between Ho and Hc is the intercept and is used in the Marc Saint Hilaire method for solving position. In previous posts we found Hs (Ref.3), Ha (Ref.4) and Ho (Ref.5). […]