Tests of topographic mapping with Thematic Mapper images

Abstract

This paper reports on research sponsored by the European Space Agency on the potential of Thematic Mapper (TM) images for topographic mapping from the viewpoint both of accuracy and content. After a thorough test with Large Format Camera images taken as ground truth, the accuracy of point positioning was assessed as ～ 50m. Severe difficulties were encountered in updating or drawing new 1:500 000 maps due to the lack of the fundamental information contained in such a map in theTM images. The use of TM images for topographic mapping on that scale is therefore discouraged.     

Quantification of interacting runtime qualities in software architectures: Insights from transaction processing in client–server architectures

ContextArchitecture is fundamental for fulfilling requirements related to the non-functional behavior of a software system such as the quality requirement that response time does not degrade to a point where it is noticeable. Approaches like the Architecture Tradeoff Analysis Method (ATAM) combine qualitative analysis heuristics (e.g. scenarios) for one or more quality metrics with quantitative analyses. A quantitative analysis evaluates a single metric such as response time. However, since quality metrics interact with each other, a change in the architecture can affect unpredictably multiple quality metrics.ObjectiveThis paper introduces a quantitative method that determines the impact of a design change on multiple metrics, thus reducing the risks in architecture design. As a proof of concept, the method is applied on a simulation model of transaction processing in client server architecture.MethodFactor analysis is used to unveil latent (i.e. not directly measurable) quality features represented by new variables that reflect architecture-specific correlations between metrics. Separate Analyses of Variance (ANOVA) are then applied to these variables, for interpreting the tradeoffs detected by factor analysis in terms of the quantified metrics.ResultsThe results for the examined transaction processing architecture show three latent quality features, the corresponding groups of strongly correlated quality metrics and the impact of architecture characteristics on the latent quality features.ConclusionThe proposed method is a systematic way for relating the variability of quality metrics and the implied tradeoffs to specific architecture characteristics.     

A preliminary assessment of Landsat TM imagery for mapping vegetation and sediment distribution in the Wash estuary

Abstract

Analysis of Landsat Thematic Mapper (TM) image of 14 May 1984 has shown that such data can be used to survey vegetation and sediment distributions in the intertidal zone of the Wash estuary at a spatial detail comparable with current methods practised by the.Nature Conservancy Council. Multispectral classification of this TM image showed good separation of salt-marsh vegetation communities which had recently been surveyed by the Nature Conservancy Council and for which reliable training data could be taken. The sensitivity of classification performance, using both parametric and non-parametric algorithms, to apparently minor differences in phenology at training site locations demonstrates two requirements for improved salt-marsh classification. They are the need for strict definition of training data and that TM wave bands 2, 3, 4 and 5 provide suitable spectral vectors for classifying intertidal environments.     

An algorithm for the identification of benthic algae in the Venice lagoon from Thematic Mapper data

Abstract

An algorithm for the identification of benthic algae in the Venice lagoon using Thematic Mapper data has been developed from a study combining water optics modelling with remote sensing routines tailored to the local situation. The sensitivity and validity range of the algorithm have been assessed by an error analysis considering both the atmospheric correction uncertainty and the masking cfTect of water turbidity. The procedure has been tested on a TM scene of 7 June 1989 yielding a thematic map which classifies algae according to depth.     

Applications of Landsat‐5 TM imagery in assessing and mapping water quality in Reelfoot Lake,Tennessee

Water quality in Reelfoot Lake, Tennessee, was investigated in the field over 15 years ago. However, the spatial variations of water quality were not studied. The remote sensing technique has been proved a powerful tool in mapping spatial distributions of some water quality parameters such as chlorophyll‐a concentration. Additionally, different regression methods and various independent variables have been used to establish relationships between water quality parameters and spectral reflectance. The results from this study indicate that Landsat TM2 and TM3, as a set of independent variables in multivariate regression analysis, are good predictors of water quality in Reelfoot Lake. TM2 is positively correlated to water quality, and TM3 is negatively correlated to water quality. Poor water quality, or a high algae load, results in a high reflectance measured by TM2 and a low reflectance measured by TM3. Maps of spatial distribution of Secchi disk depth, turbidity, chlorophyll‐a, and total suspended solids present apparent spatial variations of water quality in the lake.     

Representing time intervals in a two-dimensional space: An empirical study

ObjectiveInstead of the linear model (LM), time intervals can be represented by a two-dimensional (2D) model, which is called the triangular model (TM). Although the TM has been introduced for decades and applied in some areas, there still a lack of empirical studies on its usability. To fill this gap, this study aims to evaluate how people perform when using the TM to answer questions on time intervals, in comparison with using the traditional LM.MethodAround 250 novice participants took part in the experiment, which consisted of a video training, a pretest and posttest. The video training introduced the basic knowledge of temporal relations and the two representations. The pretest allowed participants to practice the knowledge they have learned and receive feedbacks of the answers. In the posttest, participants' accuracy and speed when answering the questions were recorded for analysis. The results of using the TM and the LM were compared in pairs. The null hypothesis is that the participants produce equal results with the two models.ResultThe results showed that the participants scored better and spent less time when answering questions with the TM, which rejected the null hypothesis. Moreover, the score and speed when they used the TM did decline in the questions containing a larger number of intervals. In contrast, the score and accuracy when they used the LM declined when questions containing a large number of intervals.Conclusion

• •The TM is easy to learn. After a 20-min training, novice participants can use it to solve questions and produce satisfactory result.
• •The TM is easy and efficient for visual queries of time intervals.
• •The TM is easy to use for handling a large number of intervals.

Implication

• •The TM can be widely applied in analysing time intervals and linear data.
• •Tools implementing the TM can be learned and used by novice users.

     

Detecting water quality parameters in the Norfolk Broads,U.K., using Landsat imagery

Abstract

The water quality parameters chlorophyll-a, total phosphorus, Secchi disk depth, suspended solids, salinity and temperature in the Norfolk Broads have been studied using Landsat TM data. An empirical approach of relating TM data with ground referenced data for these parameters through regression analysis was employed. Significant relationships were established between them. These models were used to predict and map these parameters in 27 or the Norfolk Broads. All the predicted values are consistent with the available general knowledge about these Broads     

Total forearm support during a typing task may reduce the risk of Trapezius' Myalgia development

ObjectiveEvaluate the influence of alternating the position of the upper limbs, between fully supported and unsupported forearms, in the Upper Trapezius (UT) activity during a typing task on a straight-edged desk.BackgroundErgonomic barriers, such as reduced desk area, is one of the reasons that force computer users to work without supporting their forearms. Unsupported forearms may lead to increased UT muscle fatigue, increasing the potential for lesions, with Trapezius Myalgia (TM) being a possible outcome.Method15 healthy volunteers were assessed (6 females, average age of 3,7 ± 9,5 years old). The protocol included an alternated position of forearms every 5 min between fully supported and unsupported forearms, with a 20-min total duration of a typing task. Surface electromyography readings were collected from both UTs.ResultsSignificant differences were found in the variation of the EMG signal between the two positions for the non-dominant arm after 10 min (p < .05) of typing. The non-dominant UT registered higher levels of activity than the dominant UT. Supported forearms reduced the electrical activity in both UTs, with a greater difference in the non-dominant.ConclusionThis study consolidates the current knowledge that unsupported upper limb during typing tasks significantly increases UT's electrical activity. By fully supporting the forearm, that activity is reduced. Females and the non-dominant UT showed higher electrical activity, potentially increasing the risk of developing TM.ApplicationHealthcare providers, safety and health professionals, and ergonomists should be mindful of the forearm position when advising computer users to prevent TM.     

应用Landsat TM影像估算渤海叶绿素a和总悬浮物浓度

利用23个实测样点的渤海叶绿素a和总悬浮物浓度数据及同步Landsat TM影像数据,分别分析了Landsat TM离水辐射亮度对渤海叶绿素a和总悬浮物浓度的敏感性,选择合适的波段,通过回归分析构建了基于Landsat TM离水辐射亮度的渤海叶绿素a和总悬浮物浓度反演模型。结果表明,TM1、TM2和TM3波段对叶绿素a的敏感性较高,以TM4/TM1和TM3/TM2的对数为自变量,以叶绿素a浓度的对数为因变量的线性估算模型可以有效反演渤海叶绿素a浓度,决定系数R2达到0.97;TM3波段对悬浮物的敏感性最高,以TM2、TM3和TM3/TM2为自变量,以总悬浮物浓度的以10为底的对数为因变量的多元线性模型获得的结果最佳,决定系数R2达到0.91。     

Software quality assurance economics

ContextSoftware companies invest in quality assurance in order to lower software development and maintenance cost, and to increase revenue and profit margins. To contribute to increase of net income, a quality assurance organization has to consider cost and value of the testware involved in assuring quality of software artifacts, such as requirements, specifications, designs, and code.ObjectiveThis paper proposes a set of economic metrics: testware return on investment, inflation, and cost and value sensitivity to artifact changes and time passage. The paper proposes a set of guidelines on lowering testware cost, on increasing value, on maximizing return on investment, and on when to release.MethodThis paper presents an industrial case study data on the relation between test case cost and value, and on cost and value sensitivity to time passage and artifact changes.ResultsThe industrial case study showed return on investment on test cases of up to 200%, deflation of up to −2% per month, undesirable economic effects, such as test case cost outpacing test case value and rapid test case value depreciation based on time passage.ConclusionA viable QA organization should measure and improve test case return on investment, inflation, and cost and value sensitivity to artifact changes and time passage.     

Mapping inland lake water quality across the Lower Peninsula of Michigan using Landsat TM imagery

The number, size, and distribution of inland freshwater lakes present a challenge for traditional water-quality assessment due to the time, cost, and logistical constraints of field sampling and laboratory analyses. To overcome this challenge, Landsat imagery has been used as an effective tool to assess basic water-quality indicators, such as Secchi depth (SD), over a large region or to map more advanced lake attributes, such as cyanobacteria, for a single waterbody. The overarching objective of this research application was to evaluate Landsat Thematic Mapper (TM) for mapping nine water-quality metrics over a large region and to identify hot spots of potential risk. The second objective was to evaluate the addition of landscape pattern metrics to test potential improvements in mapping lake attributes and to understand drivers of lake water quality in this region. Field-level in situ water-quality measurements were collected across diverse lakes (n = 42) within the Lower Peninsula of Michigan. A multicriteria statistical approach was executed to map lake water quality that considered variable importance, model complexity, and uncertainty. Overall, band ratio radiance models performed well (R² = 0.65–0.81) for mapping SD, chlorophyll-a, green biovolume, total phosphorus (TP), and total nitrogen (TN) with weaker (R² = 0.37) ability to map total suspended solids (TSS) and cyanobacteria levels. In this application, Landsat TM and pattern metrics showed poor ability to accurately map non-purgable organic carbon (NPOC) and diatom biovolume, likely due to a combination of gaps in temporal overpass and field sampling and lack of signal sensitivity within broad spectral channels of Landsat TM. The composition and configuration of croplands, urban, and wetland patches across the landscape were found to be moderate predictors of lake water quality that can complement lake remote-sensing data. Of the 4071 lakes, over 4 ha in the Lower Peninsula, approximately two-thirds, were identified as mesotrophic (n = 2715). This application highlights how an operational tool might support lake decision-making or assessment protocols to identify hot spots of potential risk.     

Radiometric comparison of the LANDSAT-5 TM and MSS sensors

Abstract

This paper analyses the radiometric accuracy of LANDSAT-5 Thematic Mapper (TM) data and of LANDSAT-5 Multispectral Scanner (MSS) data, using concurrent TM and MSS images recorded simultaneously over the city of Montreal, Quebec, Canada. The data sets were obtained from the Canada Centre for Remote Sensing (CCRS), and have been preprocessed for geometric correction, and for radiometric 23calibration utilizing the in-flight calibration lamp data. The comparison of the TM and MSS normalized apparent reflectances computed for 12 different typical cover types using the post-launch calibration dynamic ranges shows the relevance of the CCRS processing systems. The significant linear regressions, obtained between channels from the two sensors, and the analysis of the ground reflectance corrected for atmospheric absorption and scattering as well as for pixel adjacency effects, can serve both to assess detector degradation with time and to rescale data to match those from other LANDSAT sensors.     

The effective resolution element of Landsat Thematic Mapper

Abstract

As part of the U.K.'s contribution to NASA's Landsat [mage Data Quality Analysis (LIDQA) programme the system performance of the Thematic Mapper (TM) scanner has been studied by the determination of the Effective Resolution Element (ERE), a measure of its spatial resolution. Two methods have been used, the first by a simulation of the TM's spatial responses in an analytical model and the second by measurements of water bodies on a selected Landsat-5 TM scene. Bands 1-4 of the Thematic Mappers of both Landsat-4 and Landsal-5 have an effective resolution element by the former method of 52 m. This compares with a value of 122 m for band 4, near-infrared, of the Multispectral Scanner (MSS) by the same method. An image-derived value, by the latter method, for band 4 of the Landsat-5 TM scene is approximately 75 m. This increase in the ERE over the sensor-only value is attributed to additional factors within the imagery such as the pixel sampling of the scene, ground segment processing and the contribution of atmospheric effects. The image-derived measure of the ERE will give a useful indication of the size of targets that can be recorded to a given radiometric accuracy and can thus determine the type of informational classes that may be utilized from present methods of automated classifications of remotely-sensed data.     

Quantitative classification as a tool to show change in an urbanizing watershed

Quantitative classification of Landsat Thematic Mapper (TM and ETM+) imagery can provide a very useful medium for showing urban change at a watershed scale. It shows both the nature and the degree of urbanization with a resolution equivalent to that of the original TM image. Estimates of urbanization-related factors such as surface imperviousness and canopy cover can be coupled to illustrate the process of urban growth in the watershed using change vector analysis. When used together and combined with standard GIS data sets such as digital line graphs and digital elevation models, quantitative classification can provide the parameters needed to run standard hydrological models that can be used to describe or to forecast the effects of urbanization on area streams. Watersheds provide a meaningful scale for the analysis of the connections between urbanization and the environmental changes it brings. The study area for this paper is the Tinker's Creek watershed in northeast Ohio, USA. Tinker's Creek is one of the largest and most varied watersheds in the area, and it is subject to significant urbanization stress. Urbanization in the watershed is reflected in four TM images of northeast Ohio over a 15-year period (1984-1999). Quantitative classification provides a rich and detailed picture of urbanization over the time period of the study.     

Improving interface quality: an investigation of human-computer interaction task learning

Abstract

User learning is of critical importance in evaluating interface usability (and in turn interface quality). The focus of this research in on interface leamability, where a stochastic model represents the learning process required for successful completion of human-computer interaction tasks. The parameter used to quantify learning is a learning rale. Of interest here is the validation of learning rate as a measure of interface quality. Learning rate was validated against two traditional measures of interface quality: task completion time, and error frequency. SuperCard(tm), a Macintosh project utility, provided an empirical learning environment in which 32 participants learned 16 fundamental SuperCard tasks. Results of correlation analyses suggested the usefulness of learning rate as an indicator of interfacequality. Our learning rate analysis identified four tasks presenting learning difficulties. (Analysis of task completion times identified two of these four tasks, and error frequency analysis identified one). Learning rate data captured all of the information available from the two traditional interface quality measures and identified two tasks disregarded by them. Incorporating learning rates in the interface evaluation process precludes time-intensive video tape analysis typically required by more traditional interface quality measures.     

Comparison of a new algorithm with the supervised classifications

In this study, a new classification algorithm in which only the selected pixels have been attempted to be classified (selected pixels classification: SPC) has been introduced and compared with the well known supervised classification methods such as maximum likelihood, minimum distance, nearest neighbour and condensed nearest neighbour. To examine the algorithm, Landsat Thematic Mapper (TM) data have been used to classify the crop cover in the selected region. It is clearly demonstrated that the SPC method has the higher accuracy with comparable CPU times.     

Classification automatique assistée par une analyse de texture,des paysages de la Pointe d'Arçay d'après des données Thematic Mapper

Abstract

Cet article présente une classification automatique des unités de paysages de la Pointe d'Arçay d'aprés des données Thematic Mapper (TM), avec un algorithme de classification non supervisée d'agrégation autour de centres mobiles, en utilisant non seulement des informations radiométriques du TM mais aussi un certain nombre de caractéristiques texturales des paysages. La qualité de la classification multispectrale est améliorée par l'introduction d'une analyse de texture

An approach to automatic classification of landscape using LANDSAT-5 Thematic Mapper (TM) data is presented with an example of application for the Arçay spit (Véndee, France). First of all, using unsupervised classification of aggregation round mobile centres (the dynamic-cluster algorithm), a multispectral classification is realized withTM bands 1,2,3,4, 5 and 7, and then a texture analysis is introduced to eliminate classification confusion between certain classes. The classification quality is improved owing to the texture analysis.     

Caractérisation de formations végétales mediterranéennes à partir de données ‘Thematic Mapper’ Une étude de cas en Andalousie (Espagne)

Abstract

The study is focused on the characterization of vegetation formations in a Mediterranean area (943 km²) located in southern Spain: herbaceous canopies (rangelands), shrubby vegetation (‘matorral’) and complex woody/herbaceous formations (‘dehesa’). Vegetation formations (physiognomical units) have been characterized by their spectral responses in the six reflective TM channels and by vegetation indices. From the ratio index TM4/TM3 there has been derived a map displaying seven classes (water, bare soil and five biomass levels reflecting the hierarchy of vegetation formations). Channels TM3, TM4 and TM5 have been considered for a supervised classification into nine land-cover categories (seven vegetation formations, bare soil and water). The proportion of correct classification of vegetation formations is about 78 per cent when considering test areas. Classification made from three principal components gives similar results.