![]() UAV equipped with RTK positioning systems are also affected with the speed, but with hover at each photo taken, you can get very good accuracy. When a smaller GSD is required an altitude of 3 to 4 times the height of the highest point is recommended.įlight speed have special effect in cameras equipped with rolling shutter, while those equipped with global or mechanical shutter tends to reduce this effect. The resulting larger GSD the accuracy will be decreased as there will be less detail in the recognizable features. The higher the flight altitude, the larger the image footprint and GSD. Also consider that rolling shutter cameras produce distorted images when the UAV is moving, so global or mechanical shutter cameras are advised for mapping jobs. Weather conditions have direct impact in the photogrammetry results, so it is important to consider cloud coverage, wind speed, humidity, sun’s altitude and other factors influencing the UAV stability and terrain illumination.īigger and better sensors produce less noise and more clearly focused images. ![]() ![]() When using GCP, absolute accuracy can be improved to 2.5 times GSD for the horizontal accuracy and 4 times the GSD for the vertical accuracy (Madawalagama 2016).Īt a GSD of 1cm, the accuracy is to that of the RTK GNSS, and is within 1:200 scales according to NSDI & FGDC mapping accuracy standards during sub-optimal conditions (Barry 2013). And as for the absolute accuracy, one must consider that it is dependent of the GPS unit mounted in the UAV but the horizontal accuracy of a standard GPS is usually in the range of 2 to 6 meters and the vertical accuracy between 3 to 4 times the horizontal accuracy. In general terms, one can expect the relative accuracy to be in the order of 1 to 3 times the average GSD for the dataset. In the other hand, there are tasks on which accuracy is critical, for example project compliance evaluations and land title surveying, which require a higher relative and absolute accuracy. For instance assessing the progress in a construction site or measuring an area affected by a fire does not require the use of GCP, since absolute accuracy will not impact the decision making process. Placed correctly according to its real world positionĮach project has specific accuracy needs to be met. Model showing high relative and absolute accuracy. Figure 2 shows a relative and absolute accurate model, as the points are correctly placed according to its real world position.įigure 2. Model showing high relative accuracy but misplaced according to its real world positionĪbsolute accuracy is the accuracy of the reconstruction in relation to its true position on the planet (Pix4D 2019). Relative accuracy is independent of the location of the map in the world, so a map can have a high relative accuracy (in size and shape) but its position in the world can be shifted (Figure 1).įigure 1. Local or relative accuracy can be defined as the degree to which de distances between two points on a map correspond to the actually distances between those points in the real world. Therefore, when we refer to accuracy, we are talking about quality of data and about number of errors contained in a certain dataset (Pascual 2011). Your computer is running out of memory, what can you do?Īccuracy can be defined as the degree or closeness to which the information on a map matches the values in the real world.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). ![]()
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