ACYOTB Plugin: Tool for Accurate Orthorectification in Open-Source Environments

Abstract

High-resolution satellite images must undergo a geometric rectification process in order to be used for metrical purposes. This operation, called orthorectification, is necessary because of deformations mainly due to camera distortions and acquisition geometry. To correctly orthorectify an image, it is necessary to accurately reconstruct the photogrammetric-acquisition characteristics and the image position with respect to a reference system connected to the ground. This operation, called orientation, can be done using various mathematical models such as rigorous, rational polynomial function (RPF), and rational polynomial coefficient, or, according to some authors, rapid positioning coefficient (RPC) models. Orientation and orthorectification are usually performed within specific commercial software, but in QGIS, these complex operations can be performed using the open libraries of the Orfeo Tool Box (OTB). Unfortunately, instructions given by OTB developers lead to scarce results. In fact, the procedure proposed in OTB does not allow for the full exploitation of the potential of RPC models, on which OTB itself is based. As OTB is open-source software, a plugin was developed to overcome these limitations and exploit its full potential. In fact, OTB interfaces are unfortunately essential, and some necessary functions are missing. Therefore, a new QGIS plugin was developed in order to run the entire process in the most photogrammetrically and statistically correct way, and, at the same time, to simplify the relative procedures.

Vulnerability of Hydraulic Constructions in Flood-Prone Agricultural Areas

“…The morphometric parameters of the basins underlying the section of the building and the relative flow rates (where necessary) were obtained with an ad hoc procedure that uses GIS technology [50]. This module uses as data input: (a) the digital land model of the basin to be studied; (b) the coordinates of the closing section of the basin; (c) the threshold, expressed in the number of cells, of the drainage area in a channel.…”

Integrated Geomatic Techniques for Georeferencing and Reconstructing the Position of Underground Archaeological Sites: The Case Study of the Augustus Sundial (Rome)

“…The scaling process was handled using some targets, measured by a total station, and by a high precision steel calibrated scale bar of 800 mm (±0.05 mm). Specifically, four targets have been used as GCPs (Ground Control Points), with the aim to contain the deformations of the photogrammetric model; such deformations were estimated by means of two other targets used as CPs (Check Points) [37]. The maximum errors obtained on GCPs and CPs have been 3 mm and 8 mm respectively, while the error on the calibrated scale bar has been 0.5 mm; after that, the bundle block adjustment procedure was completed.…”

How to Orient and Orthorectify PRISMA Images and Related Issues

“…Geometric correction is a fundamental step that affects all subsequent forms of processing of the image itself and the accuracy of the final product strictly depends on the original image characteristics, on the quality of the known coordinates of ground control points and on the model chosen to perform the orientation. Satellite image processing methods and the analysis of precision and accuracy of derived products are widely investigated [22][23][24][25][26][27].…”