Assessing modern ground survey methods and airborne laser scanning for digital terrain modelling:A case study from the Lake District, England

This paper compares the applicability of three ground survey methods for modelling terrain: one man electronic tachymetry (TPS), real time kinematic GPS (GPS), and terrestrial laser scanning (TLS). Vertical accuracy of digital terrain models (DTMs) derived from GPS, TLS and airborne laser scanning (ALS) data is assessed. Point elevations acquired by the four methods represent two sections of a mountainous area in Cumbria, England. They were chosen so that the presence of non-terrain features is constrained to the smallest amount. The vertical accuracy of the DTMs was addressed by subtracting each DTM from TPS point elevations. The error was assessed using exploratory measures including statistics, histograms, and normal probability plots. The results showed that the internal measurement accuracy of TPS, GPS, and TLS was below a centimetre. TPS and GPS can be considered equally applicable alternatives for sampling the terrain in areas accessible on foot. The highest DTM vertical accuracy was achieved with GPS data, both on sloped terrain (RMSE 0.16. m) and flat terrain (RMSE 0.02. m). TLS surveying was the most efficient overall but veracity of terrain representation was subject to dense vegetation cover. Therefore, the DTM accuracy was the lowest for the sloped area with dense bracken (RMSE 0.52. m) although it was the second highest on the flat unobscured terrain (RMSE 0.07. m). ALS data represented the sloped terrain more realistically (RMSE 0.23. m) than the TLS. However, due to a systematic bias identified on the flat terrain the DTM accuracy was the lowest (RMSE 0.29. m) which was above the level stated by the data provider. Error distribution models were more closely approximated by normal distribution defined using median and normalized median absolute deviation which supports the use of the robust measures in DEM error modelling and its propagation. © 2012 Elsevier Ltd.

Improving attainment across a whole district: school reform through peer tutoring in a randomized controlled trial

Districts are an important unit for administrative purposes, but they vary little in their impact on students’ attainment, at least in the UK. Further, government attempts to raise attainment are often disappointing. The project described in this article aimed to engage schools in reform to change students’ attainment and attitudes in schools across a whole district. The intervention, peer tutoring, has a good research pedigree in small-scale studies, but scaling it up to district-level implementation has not been rigorously evaluated. Over 2 years, 129 elementary schools in 1 Scottish district were randomly assigned to different interventions. The implementation was not perfect, but the results were positive with respect to cross-age tutoring, which had effect sizes of about 0.2. Despite limitations, the study demonstrates that it is possible to carry out a clustered randomized controlled trial (RCT) on a large scale working with districts and suggests that peer tutoring has promise when scaled up.

Increasingly ‘Irrational’ Party Systems: Evidence that There Are Increasingly More Than Two at the District level

Recent work has noted an increase in the number of parties at the national level in both proportional and majoritarian electoral systems. While the conventional wisdom maintains that the incentives provided by the electoral system will prevent the number of parties at the district level from exceeding two in majoritarian systems, the evidence presented here demonstrates otherwise. I argue that this has occurred because the number of cleavages articulated by parties has increased as several third parties have begun articulating cleavages that are not well represented by the two larger parties.

In Defiance of Duverger: The Class Cleavage and the Emergence of District-Level Multiparty Systems in Western Europe

At its core, Duverger’s Law—holding that the number of viable parties in first-past-the-post systems should not exceed two—applies primarily at the district level. While the number of parties nationally may exceed two, district-level party system fragmentation should not. Given that a growing body of research shows that district-level party system fragmentation can indeed exceed two in first-past-the-post systems, I explore whether the major alternative explanation for party system fragmentation—the social cleavage approach—can explain such violations of Duverger’s Law. Testing this argument in several West European elections prior to the adoption of proportional representation, I find evidence favouring a social cleavage explanation: with the expansion of the class cleavage, the average district-level party system eventually came to violate the two-party predictions associated with Duverger’s Law. This suggests that sufficient social cleavage diversity may produce multiparty systems in other first-past-the-post systems.