GPS Coordinates from iPhone Photos: Decimal vs DMS Explained

When you extract GPS coordinates from an iPhone photo’s EXIF, you’ll see them in one of two formats: decimal degrees (e.g., 37.42196, -122.08507) or degrees-minutes-seconds (DMS) (e.g., 37° 25' 19.07" N, 122° 5' 6.24" W). They describe the same point on Earth — DMS is the older format that survives from navigation history, and decimal is the format most modern software prefers. This post explains why both exist, how iPhone EXIF actually stores them, and when to convert between them.

Short answer: iPhone EXIF stores GPS coordinates internally as degrees, minutes, and seconds (DMS) — three separate numbers per axis, plus a hemisphere reference (N/S, E/W). Most EXIF exporters convert this to decimal degrees because decimal is easier to parse, plug into Google Maps URLs, and import into databases. Decimal 37.42196 and DMS 37° 25' 19.07" N are the same coordinate; one converts to the other with arithmetic. For documentation work — Excel exports, court exhibits, claim files — decimal is almost always what you want.

A 30-second refresher on geographic coordinates

A coordinate on Earth is two numbers: latitude (how far north or south of the equator, between -90 and +90) and longitude (how far east or west of the prime meridian in Greenwich, between -180 and +180). Positive latitude is northern hemisphere; negative is southern. Positive longitude is eastern hemisphere; negative is western.

Different conventions express those numbers different ways:

Decimal degrees: a single number per axis. 37.42196 latitude.
Degrees Minutes Seconds (DMS): three numbers per axis, in base-60 like a clock. 37 degrees, 25 minutes, 19.07 seconds.
Degrees Decimal Minutes (DDM): a hybrid sometimes used in maritime contexts. 37° 25.318' N.

All three describe the same point. They differ only in notation.

How iPhone EXIF actually stores GPS

If you open the raw EXIF of an iPhone photo with a tool like exiftool, you’ll see GPS data structured something like this:

GPSLatitude    : 37 deg 25' 19.07" N
GPSLongitude   : 122 deg 5' 6.24" W
GPSAltitude    : 12.4 m Above Sea Level
GPSLatitudeRef : North
GPSLongitudeRef: West
GPSAltitudeRef : Above Sea Level

The EXIF spec stores latitude and longitude as three rational numbers (degrees, minutes, seconds) plus a hemisphere reference. The reference field is what makes a coordinate positive or negative when converted to decimal — North and East are positive; South and West are negative.

Why this format? Historical. The EXIF GPS section was modeled on the NMEA 0183 GPS protocol from the 1980s, which itself inherited from nautical navigation traditions. DMS isn’t an arbitrary choice — it predates Common Era cartography.

How to convert DMS to decimal degrees

The formula is:

decimal = degrees + (minutes / 60) + (seconds / 3600)

For our example latitude 37° 25' 19.07" N:

37 + (25 / 60) + (19.07 / 3600)
= 37 + 0.41667 + 0.00530
= 37.42196

Multiply by -1 if the hemisphere is South or West. So our example longitude 122° 5' 6.24" W becomes -(122 + 5/60 + 6.24/3600) = -122.08507.

This is what most EXIF export tools — including Photo Metadata Exporter — do internally before reporting GPS coordinates. Decimal is what comes out the other side, because it’s what users (and most downstream systems) want.

When you’d want DMS instead

DMS still appears in:

Nautical and aviation contexts: charts, NOTAMs, and AIPs use DMS or DDM
Old USGS topographic maps: the gridlines are DMS-based
Survey markers and legal property descriptions: traditional surveying retains DMS
NATO MGRS: a separate grid system, but built on DMS heritage

For Excel exports going to attorneys, adjusters, contractors, or photographers, decimal is what fits the workflow:

Pastes directly into Google Maps URLs: https://maps.google.com/?q=37.42196,-122.08507
Sorts and filters numerically in Excel
Imports into GIS software, databases, and project-management tools
Reads cleanly to a non-technical jury or carrier reviewer

How to convert decimal to DMS

The reverse formula is:

degrees = floor(|decimal|)
minutes = floor((|decimal| - degrees) * 60)
seconds = (|decimal| - degrees - minutes/60) * 3600
hemisphere = sign of decimal (+ N/E, - S/W)

For -122.08507:

|decimal|  = 122.08507
degrees    = 122
minutes    = floor((122.08507 - 122) * 60) = floor(5.1042) = 5
seconds    = (122.08507 - 122 - 5/60) * 3600 = (0.08507 - 0.08333) * 3600 = 6.24
hemisphere = West (negative longitude)

Result: 122° 5' 6.24" W. Same place.

In Excel, you can build a formula:

=INT(ABS(A1)) & "° " & INT((ABS(A1)-INT(ABS(A1)))*60) & "' " &
 ROUND(((ABS(A1)-INT(ABS(A1)))*60 - INT((ABS(A1)-INT(ABS(A1)))*60))*60, 2) & "\""

For an A1 cell containing a decimal degree value. Quote the result with N/S or E/W as appropriate for the original sign.

Precision and significant figures

A few rules of thumb worth knowing:

Decimal places	Approximate precision at the equator
0 decimals (`37`)	~111 km — city level
1 decimal (`37.4`)	~11 km — neighborhood level
2 decimals (`37.42`)	~1 km — block level
3 decimals (`37.422`)	~111 m — building level
4 decimals (`37.4220`)	~11 m — house-level
5 decimals (`37.42196`)	~1.1 m — within a room
6 decimals	~0.11 m — surveying precision

iPhone’s GPS chip is good for ~3-5m outdoor accuracy in good conditions, which corresponds to 4-5 decimal places. Five decimal places is what most EXIF exports use. Reporting more than 5 decimals is misleading precision — the underlying GPS fix isn’t that accurate.

For altitude, iPhone reports in meters with ~3-5m of jitter, often noisy enough that two photos in the same room can show different altitudes. Use altitude as approximate (“at ground floor / second floor” granularity), not as a precise measurement.

”Why are my coordinates negative?”

Decimal degrees use signed numbers to express hemisphere:

Latitude: positive = North, negative = South
Longitude: positive = East, negative = West

So a coordinate like -122.08507 is 122.08507 degrees West. There’s no error — that’s how decimal degrees encode the western hemisphere. (DMS uses a separate W letter instead.)

The Americas, including all of North and South America west of Greenland, are in negative longitudes. Most of Africa, Asia, Australia, and Europe east of Greenwich are in positive longitudes. Most of the US is in positive latitudes (north of the equator).

”Why does my exported Excel show coordinates as text, not numbers?”

If Excel imports 37.42196 as text rather than a number, sorting and arithmetic will break. Two common causes:

The cell is formatted as Text — change to Number or General
The coordinate has a quote prefix character ('37.42196) — strip it

Photo Metadata Exporter outputs GPS as numeric cells by default. If you’re seeing text-format coordinates and they’re causing problems, email us a sample and we’ll investigate.

”Can I paste decimal degrees into Apple Maps or Google Maps?”

Yes, both accept decimal degrees directly:

Google Maps: https://maps.google.com/?q=LAT,LNG
Apple Maps URL scheme: http://maps.apple.com/?ll=LAT,LNG
iOS Maps app: paste 37.42196, -122.08507 into the search bar

Both apps also accept DMS, but you have to type out the degree, minute, second symbols, which is awkward.

Bottom line

iPhone EXIF stores GPS coordinates as DMS under the hood, but exports them as decimal degrees because decimal is what fits modern documentation workflows. The two formats are mathematically equivalent — a coordinate doesn’t change just because the notation does. For Excel exports, court exhibits, claim files, and any other workflow where you’ll paste a coordinate into a URL, a database, or a mapping app, decimal is what you want. Photo Metadata Exporter exports decimal degrees by default with 5 decimal places of precision.