Luke Hull UAS Geospatial Applications

Introduction The use of ground control points in our data allows us to generate more accurate models and products. Ground control points assist in geo-referencing the data and improving the relative and absolute accuracy of the product. Pix4D calls for the use of a minimum of 3 ground control points but recommends to use between 5 and 10 in a data set. It is important for the pilot to use very distinguishable ground control points during data acquisition as well as keep detailed field notes on geographic locations of the points and from where the data point was taken. Ground control points can be used as checkpoints within the data set but checkpoints are not always ground control points. Checkpoints are used to assess the accuracy of the data and generated models. Differences in the initial and computed checkpoints are generated in the quality report and tell the user the amount of error within the data. Ground control points and checkpoints help the user generate and monitor an ac

Introduction What is Pix4D? Pix4D is a photogrammetry program that allows the user to generate 2D orthomosiacs, 3D surface models and point clouds with the geo-referenced imagery data they have collected. Pix4D allows for multiple different data inputs such as RGB images, thermal images and multispectral images. With Pix4D the user has the option to utilize a cloud based software and access their data and projects from multiple devices.   What Products does it generate? Pix4D generates photogrammetric models such as, but not limited to point clouds, orthomosiacs, surface and elevation models, textured 3D mesh and thermal maps.  Why is a so integral to UAS data processing? Pix4D allows the UAS user to generate products quickly and accurately from the data that was collected. Pix4D allows input from multiple common UAS sensors and does a good job at creating three dimensional models of the mission area. Pix4D does a good job at integrating flight planning and on the spo

Introduction What is photogrammetry? Photogrammetry is a 3 dimensional measuring technique that uses multiple photographs as the form of measurement. Points within each image are triangulated mathematically to produce a 3 dimensional coordinate system around specific points of interest.   What types of distortion does remotely sensed imagery have in its raw form? Remotely sensed imagery is subject to geometric distortion in its raw form, this is due to a number of reasons and varies depending on the data acquisition practices. Some of the factors that affect geometric distortion include, but are not limited to; the sensor angle, the platform altitude, the platform velocity, the platform stability, terrain changes and the curvature of the earth. These factors and distortions are visible in the raw data files and need to be corrected when applied to an orthomosiac in post processing, this will allow the user to create accurate data and images.    What is orthorectificatio