Photogrammetry Engines and Options
1. Available Photogrammetry Engines
Alteia platform integrates two industry-leading photogrammetry processing engines :
- Agisoft Metashape
These engines are built in the processing workflow and leverage the cloud-computing capacity offered by Alteia infrastructure to produce results quickly.
2. Can I process photogrammetry out of Alteia and load it ?
Yes. If you already own processed data you can load it, e.g. Orthomaps, DSM, Point Cloud. So that you can run Alteia advanced analytics without having to redo a photogrammetry process.
You can also upload data such as single pictures, and skip the photogrammetry step if :
- either not required : for instance Automatic Defect Detection and Analysis, an analytic running from single images only
- or if you want to process photogrammetry later, using Alteia first as a safe data storage.
3. What kind of dataset can I process with each of the built-in engines ?
We recommend to select :
- Pix4D for RGB, multispectral, and thermal datasets*
- Agisoft Metashape for RGB datasets only, for 3D reconstruction
- Bentley ContextCapture for 3D reconstruction
4. What happens if I upload a dataset that is not compatible ?
You may need to use occasionally other categories of datasets than your usual one. The category of data is detected during the upload process. In case that you upload a data set that is not compatible with the default photogrammetry engine, the user interface will offer you to override default setting for an appropriate alternative.
5. How to create photogrammetry presets ?
According to your business, you may require only one engine on a daily basis. It is possible to define the preferred Photogrammetry Engine as a preset for the Company (with all its sites) or within a certain Site.
5.1. For an existing Site
Step 1 - Open a Site and select Show site info from the top bar drop-down menu , which results in opening the site information panel on left side :
Step 2 - Go to PHOTOGRAMMETRY PRESETS section :
Step 3 - Select options and press Create:
This results in following confirmation message:
You can update this preset anytime later.
5.2. For an entire Company
Company Managers have administration rights allowing to define the settings that will apply across all managed Sites, per Company.
Step 1 - At the bottom of the left panel, press Administration icon :
Step 2 - Press Companies management button and select the company on the list, for which you want to adjust the photogrammetry default settings :
Step 3 - Click on Customize Preset on the Photogrammetry settings section.
Step 4. A pop-up will open with the photogrammetry settings. Adjust the settings (description given at section 6 below) and then click SAVE.
6. What are the different photogrammetry services and options ?
6.1 Pix4D Options
6.1.1 Execution mode : Self-service or Advanced
- Self-service option shall be used to get automated results from the engine without the assistance of a Alteia production member.
- Advanced option will notify the Alteia production staff and photogrammetry will be handled then delivered in the platform with their assistance and quality control.
6.1.2 Custom Settings
Selecting both Pix4D and Custom allows to set below parameters:
- Generate Light Reflectance Map: for Agriculture & Forestry projects.
- Keypoints image scale: this changes the scale of the image used to find matching features. Lower (1/2, 1/4) scales will allow projects to map faster, but with lower accuracy.
- Calibration method: this allows for the user to declare the usage of a highly accurate geolocation and orientation system (E.g. flying with RTK). Do not select this if you are unsure, as the resultant models are likely to fail.
- Point cloud image scale: This defines the scale of the images at which additional 3D points are computed. Lower (1/8, 1/4) scales produce faster, less dense clouds.
- Point cloud density: This parameter defines the density of the point cloud vs. the pixel density of the original images. The low settings produces faster, less dense clouds.
- Point cloud minimum matches: The minimum number of matches per 3D point represents the minimum number of valid re-projections of this 3D point to the images.
- DSM method: This defines the method that is used for the Raster DSM generation. The method will affect the processing time and the quality of the results.
- Orthomosaic resolution: This allows for the selection of a custom resolution in terms of GSD.
- Mesh resolution: This allows for the selection of a mesh resolution.
- Rematch: Allows to add more matches after the first part of the initial processing, which usually improves the quality of the reconstruction.
- Internal Param Optimization: Defines which internal camera parameters of the camera model are optimized.
- Radiometric Correction: Allows to calibrate and correct the image reflectance, taking the illumination and sensor influence into consideration.
- Noise filtering: selection of noise filtering
- Surface Smoothing: Selection of surface smoothing
- Orthomosaic resolution: This allows for the selection of a custom resolution in terms of GSD
6.2 Agisoft Metashape Options
- Self-Service and Advanced photogrammetry options are both available as with Pix4D
- Custom Settings: 5 profiles can be selected:
- Recommended - By default: By default settings – mainly adapted to photogrammetry processing in Mines and Quarries context.
- Recommended - Quality Medium: Same settings as “By default”, but the Dense Point Cloud is set to Medium. Mainly adapted to voluminous data sets for Mines and Quarries, Agriculture and Forestry context.
- Medium with 10cm/pixel for output rasters: Same settings as “Quality Medium”, but the output rasters (ortophoto and DSM) will be set at 10cm per pixel. To be used if the CRS is in meter. Mainly adapted to voluminous data sets.
- Medium with 3ft/pixel for output rasters: Same settings as “Quality Medium”, but the output rasters (ortophoto and DSM) will be set at 0.3ft per pixel. To be used if the CRS is in feet. Mainly adapted to voluminous data sets. NB: there is currently a display error: the setting is 0.3ft and not 3ft.
- Vegetation Encroachment: Profil to select when the photogrammetry outputs are used for the Vegetation Encroachment analytic (for Power Lines). Output rasters will be set at 25cm/pixel.