Skip to content

Commit

Permalink
Merge pull request #502 from opengisch/m-kuhn-patch-1
Browse files Browse the repository at this point in the history
EXIF fixes
  • Loading branch information
m-kuhn authored Oct 6, 2024
2 parents ade658f + 3bb4b2a commit 229f73f
Show file tree
Hide file tree
Showing 4 changed files with 7 additions and 8 deletions.
2 changes: 1 addition & 1 deletion documentation/how-to/pictures.en.md
Original file line number Diff line number Diff line change
Expand Up @@ -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 more tags visit the [QField EXIF reference documentation](/reference/exif.md) and the [exiv library documentation](https://exiv2.org/tags.html).
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
Expand Down
2 changes: 1 addition & 1 deletion documentation/reference/data-format.en.md
Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ this is inefficient.

### Use COG (Cloud Optimized GeoTIFF)

The [Cloud Optimized Geotiff (COG)](https://www.cogeo.org/) format will offer best user experience for offline basemaps.
The [Cloud Optimized Geotiff (COG)](https://www.cogeo.org/) format will offer best user experience for offline basemaps. <!-- markdown-link-check-disable-line -->
Combined with JPEG compression, it will reduce the raster size.

The following commands will convert a file called `raster.tif` to a COG file `raster_cog.tif` using JPEG compression.
Expand Down
10 changes: 4 additions & 6 deletions documentation/reference/exif.en.md
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ 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.
When using the internal 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 |
|-------------------------------------|-----------------------------------------------------------------------|---------------------------|------------------------------------------------|
Expand All @@ -15,7 +15,7 @@ When using the native QField camera, images will be geotagged with various EXIF
| 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.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) relative to magnetic north. |
| 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. |
Expand All @@ -26,10 +26,8 @@ When using the native QField camera, images will be geotagged with various EXIF
| 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.
- QField captures and stores EXIF metadata automatically when using the internal (i.e. not 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.
- See the corresponding [how to fetch geotag exif information into the attribute table section](../how-to/pictures.md#fetching-geotags-exif-from-the-image-file-into-the-attribute-table) for instructions how to make use of this
1 change: 1 addition & 0 deletions mkdocs.yml
Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,7 @@ nav:
- Technical reference:
- reference/index.md
- reference/data-format.md
- reference/exif.md
- QFieldCloud:
- reference/qfieldcloud/concepts.md
- reference/qfieldcloud/projects.md
Expand Down

0 comments on commit 229f73f

Please sign in to comment.