How High Above Sea Level Am I?

Last updated 2026-10-21 · MapElevation

What height above sea level means

A height requires a reference. Saying that a place is above sea level sounds straightforward, but the physical ocean moves and the Earth is not a simple flat surface. Mapping organisations therefore use defined vertical references to make height values meaningful across an area. The number becomes interpretable only when you know both the reference and the feature whose height was measured.

For this tool, the feature is the modeled surface at a coordinate. The current global source is Copernicus GLO-30, with the EGM2008 geoid as its vertical reference. That reference is not a live observation of a nearby beach, harbour, or tide gauge. It supports consistent terrain heights, while a local water-level question can require different information. The elevation data accuracy guide identifies the source and explains what is currently active.

How to use this page

1. Select a position using the map, an address, or the location button.
2. Read the elevation together with the source’s vertical reference.
3. Check what another number actually measures before comparing heights.
4. Use a supported professional transformation when a datum conversion is required.

Find your height above sea level

Choose an input method appropriate to your question. If you are at the location, press the browser-location button and review the returned pin. If you have a known position, use the elevation finder. If you have a complete US address, the address elevation finder first matches that address to a coordinate. Each route ends with a terrain sample, so the source limitations remain relevant whichever input you choose.

Read the result card in the units you prefer, then check the source and reference. For what is my elevation, the answer is the height associated with the returned position rather than a direct measurement of the device. A phone indoors or on an upper floor may be above the surface represented by the dataset. A terrain lookup cannot resolve that distinction by adding decimal places.

Mean sea level, geoids, and vertical datums

A geoid is a gravity-related reference surface used in height systems. A vertical datum defines the framework used to report heights in a particular dataset or jurisdiction. These concepts help explain why different authoritative sources can report different values for apparently similar locations. They do not imply that one can always be converted to another with a single constant added everywhere.

The NOAA National Geodetic Survey geoid explanation introduces the relationship between ellipsoidal and orthometric heights. NOAA VDatum describes transformations among supported vertical datums. A transformation has a geographic area, input assumptions, and uncertainty; its existence does not mean that every dataset or location is covered. Our current tool preserves source reference labels and does not infer a transformation when one has not been validated.

Why GPS altitude can differ from map elevation

A GPS receiver can estimate a height relative to a mathematical ellipsoid. Software may then apply a model or other correction before displaying altitude. A phone can also combine different sensors. Without knowing that processing, the word “altitude” on a screen does not identify the same measurement as a geoid-referenced surface pixel.

Horizontal differences matter too. A coordinate that falls across a road, down a slope, or on a nearby structure can return another modeled height. Source collection dates and surface objects create further differences. Compare source, datum, units, coordinates, and the physical feature before interpreting a discrepancy. A metres-to-feet conversion resolves only the units.

What negative elevation means

A negative terrain value means the modeled surface lies below the dataset’s reference zero. It does not, by itself, describe the depth of water, prove an ocean connection, or predict future inundation. Inland depressions and protected lowlands require a different interpretation from an open coast. The sea level rise map explains why its demonstration starts from a defined ocean connection and labels its simplified baseline assumption.

Even a connected low area can be influenced by features omitted or misrepresented in a coarse model. A narrow barrier, drainage structure, or protective work may be smaller than the dataset can reliably describe. Model limitations can change the direction of an error, so a confident-looking overlay should not replace local engineering information.

Why elevation alone does not predict flooding

For a US property, flood zone by address checks a mapped designation rather than inferring it from height alone. A base flood elevation by address lookup concerns a flood-study water elevation, not the ordinary surface elevation. The flood zone codes guide helps distinguish these map concepts.

A valid numerical ground-to-flood comparison also needs matching references and an appropriate ground or building measurement. This version does not treat GLO-30 as a surveyed lowest adjacent grade. A reproducible reference-comparison example is awaiting a verified coordinate, source pair, and transformation record; no numerical offset is assumed for illustration.