Journal of Surveying Engineering

This article deals with the characteristics of deformation of a body or a figure represented by discrete points of geodetic network. In each point of geodetic network kinematic quantities are considered normal strain, shear strain, and rotation. They are computed from strain and rotation tensors represented by displacement gradient matrix on the basis of known point displacement vector. Deformation analysis requires the appropriate treatment of kinematic quantities. Thus statistical properties of each quantity in a single point of geodetic network have to be known. Empirical results have shown that statistical properties are strongly related to the orientation in single point and local geometry of the geodetic network. Based on the known probability distribution of kinematic quantities the confidence areas for each quantity in a certain point can be defined. Based on this we can carry out appropriate statistical testing and decide whether the deformation of network in each point is statistically significant or not. On the other hand, we are able to ascertain the quality of the geometry of the geodetic network. The known characteristics of the probability distributions of two strain parameters and rotation in each point can serve as useful tools in the procedures of optimizing the geometry of the geodetic networks.

The rangefinder offset, additive constant or zero error is the most basic systematic error affecting the accuracy range measurements. Recent investigations of different systems that feature range measurement have shown that minimally constrained self-calibration adjustments of observations corrupted by an unmodeled rangefinder offset yield near-linear patterns in the range-observation residuals. This paper explains the underlying mathematical cause of this phenomenon for the purpose of assisting systematic error model identification. As a result of the mathematical derivations a new improved (in terms of parameter correlation) method for estimating the rangefinder offset from the sum of residuals of a least-squares adjustment of biased range observations has been developed. The new method is successfully demonstrated on data collected with total stations and ultrawide band ranging radios over two one-dimensional baselines.

This technical note introduces a rigorous calculation of “local accuracies.” The term local accuracies refers to the relative error between two arbitrary points (uncertainty of one point with respect to the other), expressed in a local horizon three-dimensional reference frame $\left(e,n,u\right)$ , that were connected using any geodetic-surveying methodology [optical procedures, global positioning system (GPS), etc.]. It is calculated as a function of the full global Cartesian variance-covariance matrix of the $\left(x,y,z\right)$ coordinates of the points defining the spatial network.

This technical note presents the results of a study focused on the evaluation of laser beam divergence and its effect on the spot size of terrestrial laser scanners. For this purpose, experiments were accomplished using the Leica HDS3000 and HDS6000 laser scanners. Two methods for the evaluation of the spot size are compared: a direct method, based on the analysis of the capacity of the laser beam to go through small slots, and an analytical method that estimates the spot diameter based on the edge effect. Based on the performed experiments, the development of a conceptual model of the edge effect at sharp edges is described for each method and validated. The experiments proved that the methods are suitable to analyze the variation of the diameter of the spot as a function of the distance. The estimate of the spot size using slots of varying sizes is a direct and easy to use method, but the computation of the spot size using the sharp edge model is more stable in relation to the point density, and can be used to estimate the divergence of the laser beam and the expectable spot size before a survey is performed.

The aim of this article is to review the potentiality and reliability of the integrated usage of global positioning system (GPS), terrestrial laser scanner (TLS), and total station survey measurements in the geomorphologic studies. Test surveys based on these techniques were done in the area of “Tana della Volpe” blind valley and in the adjacent “Monticino” quarry, near Brisighella, Ravenna, Northern Apennines, Italy. Such sites are characterized by peculiar geomorphologic attributes such as the presence of slope, karst, and anthropic forms. We surveyed about 18,000 GPS points and about 42,200,000 TLS points in a total of 22 scans. The processing of the survey’s whole data set produced three distinct arrays of three-dimensional (3D) coordinates complemented by orthometric heights. Moreover, an integrated multistep procedure was implemented based on the following premises: (1) the removal of points not referred to the bare earth surface; (2) the combination of three coordinate sets into a single one referred to the whole study; (3) the generation of a bare earth digital model; and (4) the elaboration of a unified contour map. The resulting high correspondence between the observed forms and the 3D models was used to realize a detailed thematic geomorphologic map by means of which it is now possible to locate and highlight the forms observed in the field. In particular by means of TLS measurements we found a maximum difference in the spatial attitude of the observed discontinuities of 5.6° and some interesting coincidences in the evaluation of the joint roughness of several centimeters.

High-resolution gravity data are efficiently collected by using a ground-vehicle-based inertial navigation system/global positioning system (INS/GPS) gravimetric system due to its closeness to the terrain and relatively speedy process. Previous studies have shown that this system has better than 1 mGal repeatability. However, the validation of the absolute precision is limited by the availability of ground control data and the selected interpolation method. Careful comparisons of the gravity estimates with independent ground control are necessary to arrive at a better knowledge of the system’s precision. First, several interpolation schemes are designed to interpolate the control data to known values along the ground tracks. The computation results show that the least square collocation method provides the most accurate interpolates of the surface data set, while the three-dimensional multi-quadrics method works well after applying the terrain correction. The best-estimated control data used have better than 3 mGal precision agreement with the wave-correlated gravity estimates obtained at the tracks of the INS/GPS gravimetric system.