First, GDOP and Geometric Dilution of Precision — same thing, page 318 — Page 391, Lesson 393

We're looking at the index of the Radio Navigation manual — the map of everything we'll cover. Let me walk you through the entries that start with G and H, because these are the terms you'll be tested on. First, GDOP and Geometric Dilution of Precision — same thing, page 318. This is a measure of how the geometry of the satellites you're using affects the accuracy of your position fix. If the satellites are spread out well, you get a good fix. If they're clustered together, your accuracy degrades. That's the dilution — the precision gets "diluted" by poor geometry. Next, Geostationary SVs on page 321. SV stands for Space Vehicle — that's a satellite. A geostationary satellite orbits at a height where it stays fixed over one spot on the equator, so it appears stationary from the ground. These are used in augmentation systems. Gigahertz on page 5 — that's a frequency unit, one billion cycles per second. You'll see it in radar and satellite communications. Then we have the ILS family. Glide Path on page 148, Glide Path Indications on page 157, and Glide Slope on page 154. The glide slope is the vertical guidance beam that tells you the correct descent angle to the runway. The glide path is the actual trajectory you fly down that beam. The indications are what you see on the instrument — the needles that show if you're above or below the correct path. GLONASS on page 305 — that's the Russian satellite navigation system, the counterpart to GPS. GNSS on pages 261 and 305 stands for Global Navigation Satellite System — the umbrella term covering GPS, GLONASS, and others. GPS itself is on page 305, the American system. Goniometer on page 88 — this is a device used in older radio direction finding. It measures the angle or bearing of an incoming signal by comparing the outputs from two crossed loop antennas. GPS and GLONASS together on page 322 — that's about using both systems combined for better coverage and accuracy. GPS Errors on page 317 covers the sources of inaccuracy, and GPS Segments on page 307 refers to the three parts of the system — the space segment, the control segment, and the user segment. GPS Time on page 307 is the precise time reference the system uses. Ground Based Augmentation Systems on page 319 — these are ground stations that broadcast corrections to improve GPS accuracy for approaches. Ground Monitoring of ILS on page 151 — that's the equipment on the ground that continuously checks the ILS signals are within tolerance. Ground Speed on page 252 — your speed over the ground, as opposed to airspeed. Guidance on page 147 — the information that tells you how to steer to stay on a desired path. Now the H entries. Half-wave Dipole on page 55 — that's a basic antenna, a conductor that's half the wavelength of the signal it's designed for. Harmonization on page 191 — aligning or matching different systems or instruments. HDOP on page 318 — Horizontal Dilution of Precision, the same geometry concept as GDOP but specifically for horizontal position accuracy. Heterodyning on page 44 — that's the process of mixing two frequencies to produce a new frequency, used in radio receivers. HF Communications on page 32 and High Frequency (HF) on page 8 — the frequency band from 3 to 30 megahertz, used for long-range voice communication. Hold on page 220 and Holding on pages 91 and 96 — that's the racetrack pattern you fly to delay while waiting for clearance. Holding Area on page 96 — the airspace where you fly that pattern. Holding points on page 160 — specific positions on the ground, usually at runway intersections, where aircraft wait before takeoff. Finally, Homing — the entry is cut off, but homing is flying directly toward a radio beacon or station, keeping the needle centered. That's the G and H section of your index. Every one of these will come up in detail as we work through the chapters.