This paper introduces a new method to analyze the positional accuracy of georeferenced satellite images without the use of ground control points. Compared to the traditional method used to carry out this kind of analysis, our approach provides a semiautomatic way to obtain a larger number of control points that satisfy the requirements of current standards regarding the size of the set of sample points, the positional accuracy of such points, the distance between points, and the distribution of points in the sample. Our methodology exploits high quality orthoimages, such as those provided by the Aerial Orthography National Plan (PNOA)—developed by the Spanish National Geographic Institute—and has been tested on spatial data from Landsat 8. Our method works under the current international standard (ASPRS 2014) and exhibits similar performance than other well-known methods to analyze the positional accuracy of georeferenced images based on the use of independent ground control points. More specifically, the positional accuracy achieved for a Landsat 8 dataset evaluated by the traditional method is 5.22 ± 1.95 m, and when evaluated with the proposed method, it exhibits a typical accuracy of 5.76 ± 0.50 m. Our experimental results confirm that the method is equally effective and less expensive than other available methods to analyze the positional accuracy of satellite images.

In this paper, ALBA, A parallel Language Based on Actors, is introduced. ALBA [15] is a new programming language designed to take advantage of highly parallel architectures that use message passing as the fundamental low-level interaction primitive. ALBA is being developed as implementation language for the QUATRO parallel Database machine [5] in order to facilitate its portability and permit a homogeneous description of the QUATRO system to every multiprocessor machine.ALBA is a strong-typed language, and is oriented towards the development of both parallel and distributed applications. The actor paradigm in ALBA presents new characteristics such as the use of broadcast methods; dynamic actor allocations permitting the programmer to distribute actors on the machine, in a load-balancing way, on both a specific set of virtual processors or on all of the processors of the machine; different communication and synchronization mechanisms among actors, and others that are presented in this papcr.The ALBA programming language and the QUATRO Database Machine are being developed under the HELIOS operating system for a transputer machine.