Trends and concerns in digital cartography

CISRG discussion paper ;

Theoretical Lidar Point Density for Topographic Mapping in the Largest Scales

When ordering LiDAR data, LiDAR point density per surface unit is important information with decisive influence on the price of the LiDAR survey. The paper first deals with the theoretical calculation of the minimum LiDAR point density, necessary for the acquisition of topographic data of the largest scales. For this purpose the sampling theorem is used. However, since topographic objects (roads, water bodies, etc.) and phenomena represented on topographic maps and in topographic bases are in many cases located under vegetation, also the rate of laser beam penetration through vegetation for the area where the topographic data are to be gathered has to be known. In a research on a test case conducted in the area of the town Nova Gorica we calculated the rate of laser beam penetration for four different vegetation types: scarce Mediterranean vegetation, thick thermophilic deciduous forest, mixed vegetation (meadows, orchards and forest) and built-up area. By connecting the theoretic minimum LiDAR point density with the rate of penetration, we defined the minimum LiDAR point density for the needs of data acquisition on topographic maps of the largest scales or in topographic bases of comparable detail (from 1 : 1000 to 1 : 10,000)

Testing implementations of Visvalingam's algorithm for line generalisation

There are a growing number of open source and commercial implementations of the Visvalingam algorithm for line generalisation. The algorithm provides scope for implementation-specific interpretations, with different outcomes. This is inevitable and sometimes necessary and, they do not necessarily imply that an implementation is flawed. The only restriction is that the output must not be so inconsistent with the intent of the algorithm that it becomes unusable. This paper provides some ideas, data and sample output to help users compare the output from their implementations with those produced by Visvalingam. This may help them ascertain whether some problems they may encounter appear to be specific to their implementation or whether they are a general feature of the algorithm. This paper assesses the utility and limitations of the Mapshaper options for Visvalingam’s algorithm. Similar, but not identical, depictions of coastlines are produced by Visvalingam’s implementation and by Mapshaper. However, the programs produce very dissimilar output for the rectangular Koch island, also known as the quadratic Koch island - Mapshaper’s output is unbalanced for both its Visvalingam and Douglas-Peucker options. This suggests that the problem, which is not immediately obvious, is in some function inherited by both options. Both programs produce near identical output when Mapshaper’s Visvalingam/weighted area option was compared using coastlines. This suggests that the problem arises from Mapshaper’s treatment of equal-valued metrics; this can be changed. Implementers and users may wish to use the data and methods given in this paper to test their own implementations if and when necessary

Mathematical-geographical analysis of the orientation of St John’s church of the Studenica monastery

Considering the fact that ecclesiastical rules do not precisely say that a church must be directed “to the East” or “to sunrise”, it should always be checked if there is a connection between the orientation of a church and geometry of the Sun. In this paper, such examination is performed on the example of the church of St. John (the 13th century), one of four churches of the Studenica monastery, in the following way: 1) using gnomon method, the azimuth of the main longitudinal axis of the church is measured; 2) the altitude above the horizon of the point in which the extended axis of the church touches the true horizon is determined by cartometry; 3) the most probable dates when the Sun rises at that point are determined: May 7th according to Gregorian calendar, or April 30th according to Julian calendar, in the 13th century. The applied method is described in details and it can be applied for the analysis of the orientation of any other medieval church. This method can determine the time when the church was founded, as well as the fact if the church is original, or possibly erected on the foundations of some older sacral object

La Persistència del traçat de Guerau (1644) a la planimetria de la Ciutat de Mallorca

Amb el precedent d'un projecte de fortificació de 1596, el primer plànol imprès de Ciutat de Mallorca –ara Palma– correspon al clergue Antoni Guerau (1644) i fa parell amb un de pictòric atribuït a Marc Cotto (1650 ca). El traçat d'aquests influirà notòriament en la mapística posterior que ha recollit J. Tous (2009). Aquí són analitzats una dotzena de plànols, la majoria militars, dels arxius francesos i espanyols a fi d'aclarir-ne l'entroncament. El disseny de Guerau perdura almenys fins a mitjan segle xviii quan els enginyers de l'Acadèmia de Barcelona intervenen. El plànol de L. Scheidnagel (1871) obre la modernitat tècnica. Hom malda per confirmar cartomètricament l'evolució del traçat i les filiacions.After a project of a plan in a project of fortification in 1596, the first printed plan of the City of Mallorca, now Palma, was created by the priest Antoni Guerau (1644) and it could be paired with another painted map attributed to Marc Cotto (1650ca). The design of both maps had an important influence in the subsequent cartography of the city gathered by J.Tous (2009). In this paper, a dozen of plans are analyzed; most of them are military coming from French and Spanish archives. The design of Guerau was maintained until mid eighteenth century when the engineers of the Barcelona Academy started to intervene. The plan by L. Scheidnagel (1871) could be considered the precursor of the technical modernity. We have used cartometry tools to trace the evolution of the design.Con el precedente de un proyecto de fortificación de 1596, el primer plano impreso de la Ciudad de Mallorca –ahora Palma– corresponde al clérigo Antoni Guerau (1644) y se empareja con otro mapa pictórico atribuido a Marc Cotto (1650 ca). El trazado de ambos influirá notablemente en la mapística posterior que ha recolectado J. Tous (2009). Aquí se analizan una docena de planos, la mayoría militares, de archivos franceses y españoles a fin de establecer su filiación. El diseño de Guerau perdura al menos hasta mediados de siglo xviii cuando intervienen los ingenieros dela Academia de Barcelona. El plano de L. Scheidnagel (1871) abre la modernidad técnica. Se ha procurado confirmar cartométricamente la evolución del trazado y los entroncamientos

Basic Morphometric Characteristics for Antarctica and Budget of theAntarctic Ice Cover

On the foundation of the latest cartographical materials, obtained in the period of IGY and following years I. A. SUYETOVA carried out the complex of cartometrical works and received the following values : 1. The area of Antarctica. 2. The average altitude of the ice and rock surface in relation to the ocean level. 3. The volume and thickness of the ice of the ice sheet of Antarctica. 4. Perimeter of Antarctica. The valuation of the Antarctic perimeter as well as the latest glaciological facts allowed to make new attempts in calculating the budget of the Antarctic ice sheet. The analysis of facts necessary for calculation of the budget allowed to calculate maximum and average square miscalculations. The average square miscalculation shows the positive ice-budget of Antarctica. The valuation of the maximum miscalculation shows the equilibrium of ice in Antarctica

The Visvalingam algorithm: metrics, measures and heuristics

This paper provides the background necessary for a clear understanding of forthcoming papers relating to the Visvalingam algorithm for line generalisation, for example on the testing and usage of its implementations. It distinguishes the algorithm from implementation-specific issues to explain why it is possible to get inconsistent but equally valid output from different implementations. By tracing relevant developments within the now-disbanded Cartographic Information Systems Research Group (CISRG) of the University of Hull, it explains why a) a partial metric-driven implementation was, and still is, sufficient for many projects but not for others; b) why the Effective Area (EA) is a measure derived from a metric; c) why this measure (EA) may serve as a heuristic indicator for in-line feature segmentation and model-based generalisation; and, d) how metrics may be combined to change the order of point elimination. The issues discussed in this paper also apply to the use of other metrics. It is hoped that the background and guidance provided in this paper will enable others to participate in further research based on the algorithm

Rocky shore biotic assemblages of the Maltese Islands (Central Mediterranean) : a conservation perspective

Limestone rocky shores constitute ca 90.5% of the 272km coastline of the Maltese islands. Only some 40% of this rocky coastline is gently sloping and easily accessible. Such shores are heavily impacted with 96% of the accessible coastline dominated by tourist-related or by maritime activities. We characterized the biotic assemblages of lowland Maltese rocky shores and tested the popularly held view that given the scarce variation in physical characteristics, such shores form a homogenous habitat. Belt transects were laid perpendicular to the shoreline from biological zero to the adlittoral zone on seven Coralline Limestone and one Globigerina Limestone shores. Cover (for algae and encrusting species) or population density (for animals except sponges) were estimated using 0.5m X 0.05m quadrats placed contiguously for the first few metres and then at regularly spaced intervals. Overall, 19 faunal and 47 floral species, and 10 faunal and 8 floral species were recorded from the Coralline and Globigerina transects respectively, with 60.8% faunal and 25.6% floral species common to the two substrata. Hierarchical clustering showed that the Coralline and Globigerina transects harboured distinct biotic assemblages and identified an upper shore assemblage dominated by the littorinid Melarhaphe neritoides and barnacles, and a lower shore assemblage dominated by algae and molluscs; a mid-shore transition zone where certain species from both assemblages reached peaks of abundance was present in almost all Coralline and the majority of Globigerina transects. Differences in biota between the two types of shore are most likely primarily related to differences in microtopography and, to a lesser degree, to exposure. It is concluded that in spite of gross physical similarity, Maltese lowland rocky shores are biotically inhomogeneous, making conservation of individual sites much more important than previously thought.peer-reviewe

The Progress of Indonesia’s Administrative Boundaries Mapping after 72 years of Independence

Administrative boundaries are belong to the fundamental dataset of national base map. These information have an affect to the management of home affairs such as natural resources, tax, land administration, natural disasters. Indonesia proclaimed its independence in 1945. It means, Indonesia is 72 years old in 2017. Now, One Map Policy becomes one of hot issues in Indonesia especially for geospatial society. Every region needs definitive administrative boundaries for their activity but not available yet for all region. This paper aim is toexplain the development or trend of Indonesia\u27s administrative boundaries mapping after 1945 in order to get the information of Indonesian government performance in the “national boundary making”. The method of this research is comparing the spatial and numerical data of Indonesia\u27s administrative boundaries which are limited to the province and regency/city boundaries.The result of this research shows that there are 3 significant periods which are affect Indonesia\u27s administrative boundary mapping i.e. 1998-2005, 2006-2012, and 2013 to this day.The conclusion of this studyis the definitive boundariesof The Republic of Indonesia in 72 years after independence reached 472 segments or 48.31% of total 977 segments

Geometric data for testing implementations of point reduction algorithms : case study using Mapshaper v 0.2.28 and previous versions

There are several open source and commercial implementations of the Visvalingam algorithm for line generalisation. The algorithm provides scope for implementation-specific interpretations, with different outcomes. This is inevitable and sometimes necessary and, they do not imply that an implementation is flawed. The only restriction is that the output must not be so inconsistent with the intent of the algorithm that it becomes inappropriate. The aim of this paper is to place the algorithm within the literature, and demonstrate the value of the teragon-test for evaluating the appropriateness of implementations; Mapshaper v 0.2.28 and earlier versions are used for illustrative purposes. Data pertaining to natural features, such as coastlines, are insufficient for establishing whether deviations in output are significant. The teragon-test produced an unexpected loss of symmetry from both the Visvalingam and Douglas-Peucker options, making the tested versions unsuitable for some applications outside of cartography. This paper describes the causes, and discusses their implications. Mapshaper 0.3.17 passes the teragon test. Other developers and users should check their implementations using contrived geometric data, such as the teragon data provided in this paper, especially when the source code is not available. The teragon-test is also useful for evaluating other point reduction algorithms