Journal of Surveying Engineering

L1 norm estimator has been widely used as a robust parameter estimation method for outlier detection. Different algorithms have been applied for L1 norm minimization among which the linear programming problem based on the simplex method is well known. In the present contribution, in order to solve an L1 norm minimization problem in a linear model, an interior point algorithm is developed which is based on Dikin’s method. The method can be considered as an appropriate alternative for the classical simplex method, which is sometimes time-consuming. The proposed method, compared with the simplex method, is thus easier for implementation and faster in performance. Furthermore, a recursive form of the Dikin’s method is derived, which resembles the recursive least-squares method. Two simulated numerical examples show that the proposed algorithm gives as accurate results as the simplex method but in considerably less time. When dealing with a large number of observations, this algorithm can thus be used instead of the iteratively reweighted least-squares method and the simplex method.

The least-squares estimation exhibits a poor performance in the presence of gross errors. One of the typical approaches to control the influence of outliers is to use robust estimation techniques. The well-established geodetic reliability theory is comprised of two main components: internal and external reliability. Both reliability measures are important diagnostic tools for inferring the strength of the model validation. To gain further insight into robust M-estimation performance, the variation characteristics of internal and external reliability measures are addressed for a particular robust estimator. Theoretical analyses show that, during the iterative reweighting procedure for uncorrelated observations, the internal reliability measures as represented by minimal detectable bias become larger and larger. For purpose of illustration, a numerical example associated with a simulated geodetic leveling network is provided. As expected, for the outlying observations, their corresponding external reliability measures get smaller and smaller when the iteratively reweighted least-squares method is implemented.

This paper presents new techniques with corresponding algorithms to automate three-dimensional point-cloud georeferencing for large-scale data sets collected in dynamic environments where typical controls cannot be efficiently employed. Beam distortion occurs at the scan window edges of long-range scans on near-linear surfaces from oblique laser reflections. Coregistration of adjacent scans relies on these overlapping edges, so alignment errors quickly propagate through the data set unless constraints (origin and leveling information) are incorporated throughout the alignment process. This new methodology implements these constraints with a multineighbor least-squares approach to simultaneously improve alignment accuracy between adjacent scans in a survey and between time-series surveys, which need to be aligned separately for quantitative change analysis. A 1.4-km test survey was aligned without the aforementioned constraints using global alignment techniques, and the modified scan origins showed poor agreement (up to 8 m) with measured real-time kinematic global positioning system values. Further, the effectiveness of the constrained multineighbor alignments to minimize error propagation was evidenced by a lower average, range, and standard deviation of RMS values compared with various single neighbor techniques.

Handheld navigation global positioning system (GPS) receivers are significantly cheaper and their position determination accuracy is less than their geodetic-grade counterparts. Although the main observable in most low-cost handheld GPS receivers is the coarse acquisition (C/A) code, some receive L1 frequency observations and utilize them to smooth the code measurements. In this technical paper, we examined the use of the C/A code and L1 phase observations captured by two GARMIN eTrex receivers in a postprocessing mode. We used software applications that send low level commands to download and save the receiver data stream and convert the observations into standard RINEX file format. Nineteen baselines with different lengths were observed using the eTrex receivers and dual frequency geodetic-grade receivers. The baseline lengths were derived from the eTrex observations and compared to corresponding ones derived from the higher accuracy geodetic-grade receiver observations. Several tests were conducted to analyze the effect of potential error sources on the achieved accuracy. The results showed that low satellite angles and existing cycle slips contributed to the errors in the processed eTrex data. The implementation of a cycle slip detection algorithm and their subsequent deletion significantly enhanced the obtained baseline relative accuracy to a finally limited range of 1.8–13.4 cm/km.

This note discusses the methods for establishing highways in the State of Texas with the focus being on common-law dedication. In general, dedication is the intentional appropriation or donation of land or of an easement or interest therein by its owner for some proper public use. The elements essential to the creation of a valid dedication include a person competent to dedicate, a public purpose that will be served by the dedication, an offer of dedication, and an acceptance of the offer. Though there are, and have been, many uses for dedications, the most common use of dedication is as a highway. The existence of a valid dedication must first be based on an intention of the landowner to devote his land to public use. Whether the grantor had intent to dedicate is a question of fact. An intention to dedicate land to a public use may be evidenced by oral declarations, which may be sufficient without more to constitute an offer of dedication. A dedication is not a conveyance; therefore a writing is not necessary and the statute of frauds is regarded as inapplicable to this kind of transfer. As in the case of the intention to dedicate, the intention to accept may be presumed as a matter of law when there is no evidence sufficient to characterize the public’s use of the land in controversy. Finally, the public use need not be for any particular length of time as it need not correspond with any of the periods of time mentioned in the statute of limitations. All that is requisite is that the use should be for such a period that it may fairly be inferred that the public desire to accept exists.