SMRF is good at avoiding Type I errors (small number of ground points mistakenly classified as non-ground) but only “acceptable” at avoiding Type II errors (large number non-ground points mistakenly classified as ground). Overall the -smrf-threshold option has the biggest impact on results. The best source to read to understand how the parameters affect the output is to read the original paper An improved simple morphological filter for the terrain classification of airborne LIDAR data (PDF freely available). Should be set to a value higher than 10.Ĭhanging these options can affect the result of DTMs significantly. smrf-window window radius parameter (in meters) that corresponds to the size of the largest feature (building, trees, etc.) to be removed. Set this parameter to the minimum height (in meters) that you expect non-ground objects to be. Should be set to something higher than 0.1 and not higher than 1.2. Increase this parameter for terrains with lots of height variation. smrf-slope slope parameter, which is a measure of “slope tolerance”. The smrf filter can be controlled via several parameters: non-ground and only the ground points are used. To create a digital surface model, be sure to pass the -dsm flag.įor DTM generation, a Simple Morphological Filter (smrf) is used to classify points in ground vs. To create a digital terrain model, make sure to pass the -dtm flag. Vertically separated flight lines also improve accuracy, but less so than a camera that is forward facing by 5°.įrom James and Robson (2014), CC BY 4.0 Creating Digital Elevation Models īy default ODM does not create DEMs. To get good 2D and 2.5D (digital elevation model) results, you will require 42% overlap and sidelap for an equivalent 70% overlap and sidelap. To get good 3D results, you will require 68% overlap and sidelap for an equivalent 83% overlap and sidelap. OpenDroneMap will generate a calibration file called cameras.json that then can be imported to be used to calibrate another flight that is more efficiently flown.Īlternatively, the following experimental method can be applied: fly with much lower overlap, but two crossgrid flights (sometimes called crosshatch) separated by 20° with a 5° forward facing camera.Ĭrossgrid overlap percentages can be lower than parallel flights. To mitigate this effect, there are a few options but the simplest are as follows: fly two patterns separated by 20°, and rather than having a nadir (straight down pointing) camera, use one that tilts forward by 5°.Īs this approach to flying can be take longer than typical flights, a pilot or team can fly a small area using the above approach. James and Robson (2014) in their paper Mitigating systematic error in topographic models derived from UAV and ground‐based image networks address how to minimize the distortion from self-calibration.īowling effect on point cloud over 13,000+ image dataset collected by World Bank Tanzania over the flood prone Msimbasi Basin, Dar es Salaam, Tanzania. Automatic or self calibration is possible and desirable with drone flights, but depending on the flight pattern, automatic calibration may not remove all distortion from the resulting products. Temperature changes, vibrations, focus, and other factors can affect the derived parameters with substantial effects on resulting data. mesh-size should be increased to 300000-600000 and -mesh-octree-depth should be increased to 10-11 in urban areas to recreate better buildings / roofs.Ĭamera calibration is a special challenge with commodity cameras. texturing-data-term should be set to area in forest areas. Using this flag will increase runtime and memory usage, but may produce sharper results. ignore-gsd is a flag that instructs ODM to skip certain memory and speed optimizations that directly affect the orthophoto. Decrease this value for a higher resolution result. orthophoto-resolution is the resolution of the orthophoto in cm/pixel. Your computer is running out of memory, what can you do?.Are there other licensing options aside from the AGPLv3?.I want to build a commercial application that includes ODM.If I use the native version of the software, how can I allocate more resources for processing?.The software is not using all of my CPU cores / memory / GPU all of the times.Can I process two or more orthophoto GeoTIFFs to stitch them together?.Getting Started with Distributed Split-Merge.What Are Cloud Optimized GeoTIFFs (COGs)?.Why would one use a particular Camera Lens Model?.When are manual selections appropriate?.True: -boundary - 3D Model/Textured Mesh.True: -boundary - Digital Elevation Model.Using Potree 3D viewer module on WebODM.After it finishes (assuming you survive that long).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |