We carry out a mathematical analysis of the quadrilateral fields from Codex Santa María Asunción and compare it with similar previous results from Codex Vergara, as well as analyze fields with more than four sides from both codices. We also provide a computational tool to draw all the possible shapes of the fields. Finally, we use the concept of maximum area to test the feasibility of the areas recorded in the codices and conclude that the Acolhua were very good surveyors.

Archaeologists have long recognized that precise three-dimensional coordinates are critical for recording objects and features across sites and landscapes. Traditionally, for relatively small areas, an optical transit or, more recently, an electronic distance measurement device (EDM) has been used to acquire these three-dimensional points. While effective, such systems have significant limitations in that they require a clear line of site. Real-time kinematic (RTK) GPS/GNSS systems (Global Positioning System/Global Navigation Satellite Systems) have been available for well over a decade, and can provide quick and accurate point measurements over a wide area without many of the limitation of older technologies. The cost of such systems, however, has generally been prohibitive for archaeologists, and so their use has been rare. Recently, a new generation of low-cost systems has become available, making this technology more accessible to a wider user base. This article describes the use, accuracy, and limitations of one such low-cost system, the Emlid Reach RS, to show why this is an important tool for archaeological fieldwork.

Introduction. In Cameroon, plantain plays a major role in food security. An increase in production is necessary to satisfy the demand. Since April 2002, CARBAP has supported a monitory centre of plantain production. The main objective is to prioritise studies of production constraints and characterise commercialisation strategies, in order to improve profitability for small-scale farmers. Materials and methods. Eighteen plots were identified within farms that represent the agro-ecological and socio-economic diversity of the region. Plots were considered as the sampling unit for agronomic and pathogenic constraints analysis. Farms were considered as the sampling unit used in the socio-economic constraint analysis. For each plot, a regular survey of 50 banana plants and agronomic practices was carried out. A survey of each farm was also set for the observation of production conditions thanks to the participation of smallholders. Results. It is possible to distinguish smallholders with different levels of diversification towards plantain production. Agronomic results in the plots surveyed were judged thanks to parameters of growth, yield and pest infestation. Good/bad results on young/older plots were basically distinguished. These divisions of individuals are influenced by initial factors (varieties available for planting, former crops in the plot), means available (inputs) and technical skills in plantain cultivation. Conclusion. This method allows the detection of indicators of diversification towards plantain cultivation and allows one to check the sustainability of such strategies. It is possible to propose improved technical practices. They will be used for further local studies aimed at improving the plantain production.

In this article I discuss problems and possibilities connected with commissioned archaeology in wetlands. The cultural heritage of wetlands is threatened by large-scale infrastructure projects, and there is a need within commissioned archaeology to develop approaches and techniques for systematic surveying in wetlands. With examples from an on-going project in southern Sweden, different surveying techniques are presented together with some results and interpretations. Attempts to grasp the complexity of the wetlands right from the beginning of the project proved to be fruitful, in that the palaeoenvironmental interpretations were decisive for the selection of sites for trial excavations. Interpretation of peatland expansion through time was important for the reading of the landscape and the search for settlement sites. Some techniques for trial excavations in waterlogged peat are also presented.

Introduction. Le plantain est une culture importante pour la sécurité alimentaire en Afrique sub-saharienne. Pour mieux hiérarchiser les priorités de recherche en fonction des contraintes des producteurs, une cellule d'observation permanente a été mise en place dans le cadre d'une démarche interdisciplinaire. Matériel et méthodes. Un échantillonnage en bananeraies a couvert les zones de contextes agroécologiques distincts qui approvisionnent Douala. Les données ont été obtenues par un suivi de parcelles et d'exploitations. À l'échelle des parcelles, les observations ont porté sur les pratiques culturales, les populations de nématodes et de charançons, et les rendements. À l'échelle des exploitations, les suivis ont porté sur les fonctions économiques du plantain. Résultats et discussions. La gamme de situations culturales étudiées correspond à une diversité de contextes et d'objectifs des exploitations agricoles. Les observations effectuées sur bananiers (rythme d'émission foliaire, circonférence du pseudotronc, nombre de doigts et de feuilles vivantes, poids et longueur des doigts, poids du régime) ont permis d'expliquer comment se déterminait le rendement. Celui-ci est surtout affecté par les pertes avant récolte, en relation avec l'état sanitaire des racines et la présence de nématodes et de charançons. Ces pertes ont été maximales à la fin de la saison sèche. Le rendement est également lié au poids du régime déterminé par le nombre de doigts essentiellement lié à la croissance et à leur remplissage. Pour ce dernier caractère, les résultats obtenus ne mettent pas clairement en évidence l'incidence de la maladie des raies noires. Des améliorations du protocole de suivi sont proposées.

This paper gives an overview of navigation and positioning requirements of the European offshore oil industry in the context of consideration now being given to the role of GPS in the European Radio Navigation Plan. An outline is given of how these requirements are currently achieved and of the criticality of the operations.

This paper addresses two aspects of high accuracy GPS positioning : single point positioning and real-time kinematic positioning. In both cases, it is shown that use of the correct models significantly improves the quality of the resulting positions. In the first case, emphasis is placed on physical models, especially the satellite orbit, and in the second case, emphasis is placed on the stochastic model, i.e. understanding the statistics of the GPS observables.