Welcome to the 3DF Zephyr tutorial series.
In this guide, you will learn how to generate and customize an orthophoto with 3DF Zephyr.
This tutorial cannot be completed with 3DF Zephyr Free or Lite versions!
3DF Zephyr allows generating true orthophotos from a mesh or creating orthomosaics from a sparse or dense cloud. To explore this topic further, you can check out this quote from Wikipedia:
An orthophoto (or orthomosaic) is a geometrically corrected (“orthorectified”) picture whose scale is uniform. The photo has the same lack of distortion as a map, and, unlike standard images with a certain level of perspective, an orthophoto allows measuring true distances.
You must create a (scaled and georeferenced) point cloud or mesh in your project before generating an orthophoto in 3DF Zephyr.
Please, download and open the dataset below.
|Download Dataset – University of Udine Zip (77.3MB)|
|Download Dataset – University of Udine .Zep (487MB)|
You will notice different orthophoto generation options from the “Workflow” (1) Menu:
Once the “True Orthophoto from Mesh” (2) option has been selected, you will be allowed to choose the most suitable Orthophoto Generation Method from the “Orthophoto Wizard” window (3):
Please, notice that this window is standard for all the above-mentioned methods. Once you have picked one of them, simply click the “Next” (4) button.
You will get a preview of the orthophoto once the Orthophoto Wizard (1) setting page appears, with a green rubber band (2) defining what will be included in the deliverable. Before doing anything, make sure to select the Reference Object and the Current Coordinate reference system you are interested in.
Please, check the “Export Orthophoto” (3) flag and then click one the “Generate Orthophoto” (4) button, you can choose both the file saving path and the image file format (.tif, .png, .jpg).
That’s all! If you want to customize your orthophotos or change the export options, the next Step 3 – Learn how to customize your Orthophoto will guide you through the orthophoto settings.
The Orthophoto wizard settings are sorted out as follows:
The “closest up rotation axis” option can be used to rotate the orthophoto according to the chosen axis, or GCP. Tiles per height and Tiles per width define the numbers of vertical and horizontal tiles used to split the orthophoto into smaller tiles (fundamental for very big orthophoto or computers with a low amount of memory). Tiff pyramids level flag will allow storing inside the generated tiff orthophoto a pyramids levels layers, which can improve the display of raster data by retrieving only data at a specific resolution required for display.
– The Export section allows choosing which files and formats will be generated as output:
Note: If the DSM/DTM files are generated, Zephyr will automatically open its DEM viewer utility when the process has finished.
– The Advanced section gives you higher control over the orthophoto generation process. They are subdivided into:
Position parameters: In this subsection, it is possible to directly define the U0, V0, and U1, V1 coordinates and minimum and maximum depth (useful if you want to ignore “slices” of the reconstruction in your orthophoto).
Generation parameters: allows controlling every pixel’s color generation mode. This system is very similar to the texture generation system. We advise leaving the color balance with 1 camera per pixel; however, if you wish, you may use more cameras for a different color weight. If this happens, you may choose between an algorithm blending method:
Multiband: will use the mean to compute low frequencies and the best images to compute the high frequencies. This is usually a better choice than Mean because although it is less prone to lighting changes (usually just a little worse than mean), the resulting image will be more in focus and sharp by preserving high frequencies.
Mean: will weigh the color source depending on the view angle and the distance. Although it’s robust to lighting changes, the mean won’t keep high frequencies, so will be less in focus and sharp.
The Select Cameras subsection allows you to select the cameras used in creating Orthophotos by tag as well.
The Export Options subsection controls the visibility of control points, grid and background color.
When everything is ready, click “Generate Orthophoto” (3) and select the file destination folder in order to proceed.
It is possible to save the Orthophoto in these image formats: jpg, png, tif.
The orthophoto generation procedure is relatively linear; however, we recommend testing the generation methods to find the one that suits you best depending on the input data.
In the Verruca Fortress case study; you can see an example of how the orthophotos created in 3DF Zephyr can be used in an applied scenario.