Indicated altitude is the altitude shown by the altimeter, not corrected for pressure or temperature.

Understanding Indicated Altitude: What It Really Means for ANIT Readers

If you’ve ever heard a pilot mutter “indicated altitude” and wondered what exactly that means, you’re not alone. Altitude isn’t just “how high you are.” There are a few different ways to describe height in the air, and each one matters in the cockpit. For students exploring the ANIT content, getting a solid handle on indicated altitude helps everything else click into place—from how you read the instruments to how you plan a safe climb or descent.

What is indicated altitude, exactly?

Let me break it down with a simple definition: indicated altitude is the altitude you read directly from the altimeter. That gauge is the main instrument that tells you how high you are above a reference pressure. You don’t tweak it for weather conditions when you’re looking at the basic reading; you’re looking at the height based on the current barometric pressure setting.

Think of the altimeter as a pressure gauge in the sky. It’s not measuring “true” height by itself. It’s translating air pressure into a number you can read. The number you see on the dial is the indicated altitude, given the pressure setting you’ve chosen for the location and moment.

How the altimeter gives you that reading

Here’s the thing: the altimeter doesn’t know your height. It knows the air pressure at your location. Your cockpit has a knob (often marked with QNH or local pressure) that you turn to the current local pressure. When you set that pressure, the altimeter’s scales convert the surrounding atmosphere into an altitude figure.

Why the local pressure setting matters is simple: air pressure changes with weather and location. If you don’t set the right pressure, your indicated altitude could be off. That’s why pilots constantly adjust the altimeter as they fly from one airport to another, across different weather systems, or when weather moves in and pressure shifts.

Calibrated altitude and radar altitude: how they differ

You’ll hear about a few other altitude concepts, and they’re not just trivia. They’re tools you’ll see on charts, in training, and in the cockpit.

• Calibrated altitude: This is altitude corrected for temperature and pressure. Temperature matters because hot air rises and expands, making the true height above sea level a little different than what the raw pressure reading would suggest. Calibrated altitude gives a more accurate picture of height in relation to the actual atmosphere you’re moving through. In real-world terms, it’s a more precise estimate for performance planning, especially when you’re near the aircraft’s limit or dealing with high-density altitude conditions.

• Radar altitude: This one is different altogether. Radar altitude, sometimes called “absolute altitude,” is how high you are above the terrain directly below you. It uses radar to measure the distance to the ground, not atmospheric pressure. This is handy during approach and landing when you need a ground-proximity readout, but it doesn’t replace indicated altitude for navigation and airspace rules.

• Airport elevation and departure point: When you depart, you might hear about the airport’s elevation, which is your starting reference. It’s the height of the field itself above mean sea level. Indicated altitude, by contrast, is what you see on the altimeter once you’ve set the local pressure. The two work together in flight planning, but they’re not the same thing.

Why this distinction matters in the real world

In aviation, safety and consistency rule the day. Indicated altitude is the baseline you’ll use to maintain separation and stay on the published flight path. Air traffic control relies on standard altitude reporting, and you’ll be asked to maintain specific indicated altitudes to ensure plenty of room between aircraft.

Weather plays a role, too. If the pressure is low, your indicated altitude will read higher than your true altitude above sea level. If the pressure is high, your indicated altitude will read lower. That’s why pilots cross-check with other instruments and with ATC to stay aware of how the air mass around you is behaving.

A quick mental model can help: imagine the altimeter as a ladder connected to a barometer. The barometer feels the air pressure; the ladder shows the height after you set the pressure. If the air pressure changes but you forget to adjust the setting, the ladder tilts in the wrong direction. You’re not climbing the same distance as you think you are.

Putting it all together with ANIT topics

If you’re reviewing ANIT content, this is a good moment to connect the dots. Here’s a compact way to think about it:

• Indicated altitude = height shown on the altimeter with the local pressure setting. It’s the basic, unadjusted reading you observe in flight.

• Calibrated altitude = indicated altitude adjusted for temperature and pressure. More accurate for performance and planning in the real atmosphere.

• Radar altitude = height above the terrain below, measured by radar. Useful near the ground, not the same as indicated altitude.

• Airport elevation = the field’s height above mean sea level, a reference point for departure and planning.

Why you should care beyond the numbers

This isn’t just theory. If you’re flying or learning to read the instruments, you’ll gain confidence by understanding where the numbers come from and what they imply. Here are a few practical takeaways:

• Always set the local pressure accurately. It’s a small step with a big payoff: the altitude you’re reading lines up with what you’re actually doing in the sky.

• Cross-check between different altitude readings. If radar altitude and indicated altitude diverge, there’s usually a reason—terrain, weather, or instrument error—and it’s worth double-checking.

• Remember your environment matters. In moutainous areas, high-density altitude can make actual performance different from what the raw indicated altitude suggests. Calibrated altitude helps with those calculations.

A few relatable digressions to keep the thread engaging

If you’re curious about the tech behind these readings, think of the altimeter as a tiny, mechanical weather reporter. It’s constantly listening to air pressure and translating that into a number you can read, almost like a reporter summarizing the forecast in a line or two.

Or consider a road trip analogy: indicated altitude is the mile marker you see on a map. It tells you roughly where you are, but it doesn’t capture every bump in the road or the exact elevation change you’ll feel as you coast over a hill. Calibrated altitude and radar altitude give you extra layers of detail, just like a GPS with terrain shading and traffic updates.

Closing thought: clarity over complexity

The aviation world loves precision, and altitude is one of the clearest places to see that impulse in action. Indicated altitude is the direct read from the altimeter, based on the current pressure setting. It’s the baseline you depend on, the number that interfaces with airspace rules, ATC instructions, and your own situational awareness.

If you want to keep the idea simple as you study, hold onto this: indicated altitude is your basic altitude readout from the altimeter. Calibrated altitude and radar altitude are more specialized tools that add nuance when weather, terrain, or performance come into play. Airport elevation is a separate reference point you use when you’re planning to take off or land.

So next time you glance at that instrument panel, you’ll not only know what the readout means—you’ll feel how it fits into the bigger picture of safe, confident flight. And that awareness is what makes the skies seem a little less mysterious and a lot more navigable.