Production with SURE - Best Practices
Doing professional production with SURE is simple.
Following these simple guidelines enables you to get the best quality results in the shortest time possible.
The best results are achieved from input images that redundantly cover the area of interest. This is ensured by the overlap between consecutive images in flight strip direction and across flight strips respectively. Depending on the output product and covered scenery, we recommend:
DSM / True Ortho production - Nadir Imagery only:
minimum 80% / 30% for rural areas
minimum 80% / 60% for urban areas
80% / 80% for dense urban areas with high rises
3D Mesh - Nadir + Oblique Imagery:
minimum 80% / 60%
80% / 80% for dense urban areas with high rises
See more details here - also adapting to various cameras.
Try to have only one flight session per project. For multiple flight sessions, make sure that the projects overlap at least by one strip. After producing the True Orthophoto, blend and adjust the results in a post-processing step, e.g. with OrthoVista. You can also use the region of interest definition if you do not want to produce overlap.
For city capture we recommend 8 cm or better, for 3D Mesh 5cm GSD.
For countrywide capture and urban applications, we recommend 10 cm GSD or better.
For Bayer pattern sensors we recommend 20% higher resolution to achieve similar results.
Focal length & altitude
Large focal length leads to a reduction in accuracy for the same sensor, due to a smaller base-to-height ratio. This is often less critical for True Ortho projects than for DSM or 3D Mesh projects.
Consider radiometric loss from high altitude due to the atmosphere between the surface and the sensor.
Lidar point clouds and Lidar Trajectories (for 3D Mesh) improve the completeness of the results, in particular for situations when enough coverage/redundancy cannot be achieved from imagery alone (e.g. low-overlap flights, dense urban scenes, narrow street canyons / inner courtyards, etc.).
Use Oriented (Aero-Triangulated) Imagery. SURE supports a wide range of orientation formats (Inpho prj, gori, ...). The production of high-quality results requires high-quality orientations (error below 1 pixels). Direct georeferencing can usually not meet this requirement.
For single-machine processing use Input Images that allow SURE to skip Image Preparation. See more details on the requirements for such images at Input Images.
For Distributed Processing projects, specify uncompressed Input Images and rely on SURE Image Preparation.
Apply your color balancing and adjustments before processing with SURE. This will ensure optimal texture for True Orthophotos, Point Clouds, and Meshes. Global adjustments on the imagery (contrast, brightness, gamma correction) will have no impact on the matching quality. If you use local adjustments (such as local contrast enhancements) consider using separate matching and texturing images.
Create a shapefile delimiting the region of interest for the processing. Ensure that the input imagery fully covers the selected area.
Hint: SURE can automatically compute an Area Of Interest, delimiting the region where the maximum quality of results should be expected, due to sufficient coverage.
If large water bodies are present in the surveyed area, create a 3D shapefile delimiting all relevant water bodies.
Produce results on a small and representative area before engaging in full production. In a matter of a few hours, this will allow you to:
Gain confidence in your input data quality (e.g. Imagery and AT).
Estimate the runtime for the complete project.
Produce an illustrative set of results on which you can validate quality.
Provide your customer with a result sample to get valuable feedback.
Use hardware that follows our recommendations and follow Performance Optimization.
Avoid executing other resource-intensive applications (GPU, CPU, RAM, Hard-disk) while the SURE processing is running. Among others, the following activities are known to be very detrimental to the processing throughput: antivirus scan, disk de-fragmentation, and large file copying.
To acquire the best possible geometric quality out of Aerial Datasets, process them using the quality level Ultra. The depth precision of the reconstructed points is maximized when quality Ultra is used. A higher depth precision leads to an increase in edge sharpness and generally more accuracy in the final results.
Set the GSD parameter only if there is a requirement for the cell/pixel size for the raster products. The GSD value specified should be equal to or greater than the GSD resulting from the quality setting. Each reduction in quality level doubles the output cell size of the product. Exception: output cell size for scenario DEFAULT and quality HIGH is not doubled, to allow for full resolution DSM and True Ortho outputs in the standard processing setting.
Let SURE select the proper Tile Size for the processing. SURE chooses a tile size that ensures that the processing stays within the hardware recommendations - typically varying between 2000 and 5000 pixels affecting memory usage and processing speed. For custom tiling exceeding this, we recommend retiling with 3rd party software.
Use distributed processing. Using distributed processing, even when a single machine is in use, gives you the following possibilities:
Add nodes to the processing on demand if necessary.
Keep disk space consumption within the hardware requirements.
Product specific optimization
DSM & True Ortho Production
If you have a camera capturing both Nadir and Oblique images, create a project containing only the Nadir images. Restricting the imagery to the Nadir frames speeds up processing and guarantees True Orthos with maximum fidelity (edge & detail sharpness due to optimal observation angle and image orientation), as height information for every raster pixel is extracted. When producing a 3D Mesh additionally, set up an individual project (see remarks below) as this workflow achieves the best possible balance between throughput and quality.
Leverage the value of a Textured DSM Mesh (2.5D), which can also be generated out of a Nadir-only dataset.
3D Mesh Production
Use all the imagery available. In particular, it is essential to use all available imagery for generating high quality textured facades and vertical structures. The SURE Mesh engine will automatically use the required images and resolutions to produce a maximum quality 3D Mesh while maintaining high throughput. When producing a True Ortho additionally, set up an individual project (see remarks above) as this workflow achieves the best possible balance between throughput and quality.
With Mesh Production you can also take advantage of the 3D Point Clouds, which are automatically generated.