Add exif reference documentation

documentation/how-to/pictures.en.md

@@ -98,7 +98,7 @@ To store the EXIF information, follow these steps:
 4.  The EXIF tags that QField can capture are listed in the QGIS documentation (link above).
     However, this list might slightly varies depending on the mobile characteristics.
 5.  Capturing EXIF tags requires accessing the full physical path of the picture. Be sure to reflect this in the QGIS expression.
-   For example, the expression `exif(@project_folder + '/' + "path", 'Exif.Image.Orientation')` retrieves the orientation of the picture stored in *path*.
+   For example, the expression `exif(@project_folder + '/' + "path", 'Exif.Image.Orientation')` retrieves the orientation of the picture stored in *path*. For more tags visit the [QField EXIF reference documentation](/reference/exif.md) and the [exiv library documentation](https://exiv2.org/tags.html).
 7.  Completed! QField's now capture and store the EXIF tags in the pictures table while taking pictures.
 
 ## Maximum picture size

documentation/reference/exif.en.md

@@ -0,0 +1,35 @@
+---
+title: EXIF Data
+tx_slug: documentation_reference_exif
+---
+
+# EXIF Data in QField
+
+When using the native QField camera, images will be geotagged with various EXIF metadata fields. Below is a reference table listing the available EXIF tags, their descriptions, examples, and comments about their usage in QField.
+
+| EXIF Tag                            | Description                                                           | Example                   | Comments                                       |
+|-------------------------------------|-----------------------------------------------------------------------|---------------------------|------------------------------------------------|
+| Exif.GPSInfo.GPSLatitude            | The latitude of the location where the image was taken.                | 47.3769                    | Stored as a positive value with a reference to N/S (see below). |
+| Exif.GPSInfo.GPSLatitudeRef         | Latitude reference (N = North, S = South).                            | N                          | Determines whether the latitude is north or south of the equator. |
+| Exif.GPSInfo.GPSLongitude           | The longitude of the location where the image was taken.               | 8.5417                     | Stored as a positive value with a reference to E/W (see below). |
+| Exif.GPSInfo.GPSLongitudeRef        | Longitude reference (E = East, W = West).                             | E                          | Determines whether the longitude is east or west of the prime meridian. |
+| Exif.GPSInfo.GPSAltitude            | The altitude above sea level (in meters) where the image was taken.    | 490                        | Positive values indicate above sea level; negative values indicate below. |
+| Exif.GPSInfo.GPSAltitudeRef         | Altitude reference (0 = Below Sea Level, 1 = Above Sea Level).         | 1                          | Indicates whether altitude is above or below sea level. |
+| Exif.GPSInfo.GPSImgDirection        | The direction in degrees in which the camera was facing when the image was taken. | 270                        | Represents the compass direction (0 = North, 90 = East, 180 = South, 270 = West). |
+| Exif.GPSInfo.GPSImgDirectionRef     | Direction reference (M = Magnetic North).                             | M                          | Specifies whether the direction is relative to magnetic north. |
+| Exif.GPSInfo.GPSSpeed               | The speed of the device when the image was taken, in kilometers per hour (km/h). | 30.5                       | Captured if the device is moving at the time of image capture. |
+| Exif.GPSInfo.GPSSpeedRef            | Speed unit (K = kilometers per hour).                                 | K                          | Currently, speed is recorded in kilometers per hour in QField. |
+| Exif.GPSInfo.GPSDateStamp           | The date the image was captured in UTC.                               | 2024:10:06                 | Date stored in the format YYYY:MM:DD. |
+| Exif.GPSInfo.GPSTimeStamp           | The time the image was captured in UTC.                               | 14:23:56                   | Time stored in the format HH:MM:SS. |
+| Exif.GPSInfo.GPSSatellites          | The number of satellites used for GPS information.                    | 12                         | Number of GPS satellites that contributed to location accuracy. |
+| Exif.Image.Make                     | The make of the device that captured the image.                       | QField                     | Always set to "QField" to indicate the software used. |
+| Xmp.tiff.Make                       | XMP tag for the device make, also set to QField.                      | QField                     | Similar to Exif.Image.Make, used for compatibility in XMP metadata. |
+
+## Notes
+- QField captures and stores EXIF metadata automatically when using the native camera. 
+- The coordinates (latitude and longitude) are always stored as absolute values, with the hemisphere indicated by the corresponding reference tags (e.g., `GPSLatitudeRef` for N/S).
+- Altitude is recorded as a positive or negative value depending on whether the elevation is above or below sea level, with `GPSAltitudeRef` used to indicate the direction.
+- Speed and direction are recorded if the device is moving and the orientation and speed sensors are active at the time of capture.
+- Date and time stamps are stored in UTC format for consistency across locations.
+
+This reference should assist in understanding the metadata captured during geotagging and how to interpret or extract EXIF data from images taken in QField.