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: EXIF GPS latitude and longitude use rational values plus hemisphere references. Metadata readers often render those values as DMS or convert them to signed decimal degrees. Decimal 37.42196 and DMS 37° 25' 19.07" N are the same coordinate after rounding. Choose the notation required by the receiving workflow, and keep accuracy separate from display precision.

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.

The representation follows the EXIF GPS tag structure. A reader can display the rationals directly or convert them to another notation without changing the underlying location value.

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 Photo2XL — 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
Is widely accepted by mapping and data tools

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
4 decimals (`37.4220`)	~11 m
5 decimals (`37.42196`)	~1.1 m
6 decimals	~0.11 m

These distances describe decimal rounding at the equator, not the accuracy of a recorded GPS fix. Actual horizontal and vertical accuracy varies with capture conditions and the stored location data. Extra digits preserve a numeric representation; they do not create measurement accuracy.

Photo2XL exports coordinates with six decimal places for consistent spreadsheet values and can include available horizontal or vertical accuracy fields separately. Do not infer a floor, boundary, or exact device position from decimal places alone.

”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 sign is part of the coordinate, not an error. Confirm latitude/longitude order and hemisphere before using the value downstream.

”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

Photo2XL 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

EXIF GPS rationals can be displayed as DMS or converted to decimal degrees. The two notations can represent the same location, subject to rounding. Choose the notation required by the receiving tool and keep source accuracy in view. Photo2XL exports decimal degrees with six decimal places and reports available accuracy fields separately; those digits are formatting, not proof of precision or provenance.