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.     

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.     

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.     

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     

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.     

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.

     

Development of principal component analysis applied to multitemporal Landsat TM data

Abstract

A method of extracting different crop information more effectively, by applying principal component analysis to a three-dimensional three-date Landsat TM data space, has been developed. Landsat TM data obtained on 7 June, 9 July and 26 August 1984 were used to examine the approach, and the results fully demonstrated its advantages over other methods of keeping classification accuracy without any calibrations for multitemporal Landsat data.     

Application of thematic mapper short wavelength infrared data for the detection and monitoring of high temperature related geoenvironmental features

Abstract

The short wavelength infrared region (0·7-3·0μm) has manifold applications in the detection and monitoring of geoenvironmental features, such as coal mine fire, oil well fire, active volcanoes, industrial hot spots, etc. These features are essentially characterized by high temperatures and often release aerosols and greenhouse gases into the atmosphere. In the present article, an attempt has been made to study the applications of Thematic Mapper (TM) Short Wavelength Infrared (SWIR) bands (4, 5 and 7) data for the detection and monitoring of these high temperature related geoenvironmental features. The rationale of using the SWIR data for temperature related studies is also discussed in brief. The pixel-integrated and sub-pixel temperatures have been calculated using the TM SWIR bands data for an active volcano (Barren Island volcano), coal mine fire (Jharia Coal Field) and industrial hot spots (Bokaro Steel Plant).     

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.     

Tropical forest typo mapping and monitoring using remote sensing

Abstract

The Andaman Nicobar group of islands in the Andaman Sea are blessed with luxuriant tropical vegetation. During recent years, vegetation in these islands has been under tremendous pressure due to increased settlement and commercial extraction, Landsat TM data of the Baratang forest division of the Andaman group of islands has been used to prepare forest type maps using visual and digital methods. Digital enhancement techniques have been evaluated to discriminate forest types in a typical environmental set-up. The mapping techniques have been compared with respect to classification and accuracy levels. Finally, the land transformation in the forest division has been studied using past aerial photographs. The study highlights the appropriate methodology required to map forest types.     

Evaluation of the potential of the Thematic Mapper for marine application

Abstract

The potential of the Thematic Mapper (TM) on board Landsal-5 for marine applications has been investigated with reference to the well-known performance of the Coastal Zone Color Scanner of Nimbus-7. The study consisted of (a) a sensitivity analysis, considering such fundamental error sources as retrieval algorithm sensitivity, atmospheric correclion, instrument noise and signal digitization and (b) the interpretation of a TM scene by the procedure suggested in (a). The evidence provided by the experimental test validated the positive conclusions of the theoretical work, indicating that the analysis of TM bands 1 to 4 data should be capable of yielding quantitative information of satisfactory quality on fundamental water quality parameters, such as chlorophyll (i.e. phytoplankion) and suspended sediment concentrations.     

Monitoring snow area and depth with integration of remote sensing and GIS

Abstract

This article reports recent progress in monitoring snow area and snow depth over the U.K. using NOAA AVHRR data. A series of transportable programmes have been developed and updated for data calibration and navigation. The establishment of a database registered to the British National Grid enables the generation of subsequent thematic overlays for any selected area. Results of snow area mapping and estimation have been validated by means of high-resolution Landsal TM data and data from U.K. Meteorological Office Snow Survey Reports. Assignment of snow depth values has also been attempted. The integration of remote sensing and GIS has facilitated the work, and will be further deployed.     

Technical note Evaluation of Rajas than desertic terrain,India, for logistic support in oil exploration using Landsat Thematic Mapper data

Abstract

The desertic terrain of Rajaslhan, India, has been evaluated to work out the logistics relevant to planning a hydrocarbon exploration programme. The digitally enhanced, high-resolution Landsat-5 Thematic Mapper (TM) and SPOT data has helped in identifying various aeolian landforms. Sand dunes are most conspicuous. On the basis of sand-dune abundance, their amplitude, wavelength and direction, three land systems have been identified in the area. The gcomor-phic information extracted from the aforesaid satellite data has been used to assess each land sysem for its feasibility for seismic profiling, drill-site construction and groundwater location.     

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.     

Remote sensing of phytoplankton An attempt from the Landsat Thematic Mapper

Abstract

An atmospheric correction scheme using Landsat Thematic Mapper (TM) bands 1, 2 and 4 was developed and the data corrected for atmospheric effects due to Rayleigh scattering and aerosols. Secondly phytoplankton pigment mapping was achieved through substitution of corrected radiances in TM bands 1 and 2 into a bio-optical algorithm developed for the study area off Azhikal in the Arabian Sea. A C map showing near-surface concentrations of phytoplankton pigments (mgm_?3)and a K map showing the pigment distribution (m?1) in one attenuation length were generated.     

Capabilities of Landsat-5 Thematic Mapper (TM) data in regional mapping and characterization of inland valley agroecosystems in West Africa

This study demonstrated the capabilities of Landsat-5 Thematic Mapper (TM) data in regional mapping and characterization of inland valley (valley bottoms plus valley slopes or fringes) agroecosystems. A methodology was developed involving image enhancement, display and digitizing, as well as image and Geographical Information System (GIS) manipulation techniques for rapid studies of inland valley characteristics over large areas. A case study was conducted using Landsat-5 TM data over the regions of Save and Parakou in the Republic of Benin (path: 192, row:54 of Landsat TM World Reference System) encompassing about 3.12 × 10⁶ha (study area) to highlight the strengths of the methodology. The results showed the ability of TM data, using the espoused methodology, to map inland valley characteristics: (a) as well as or better than 1 : 200000 topographic maps; and (b) to a significantly similar level to that of 1 : 50000 topographic maps. The technique involving a ratio image of TM4/TM7 (red), TM4/TM3 (green) and TM4/TM2 (blue) when displayed in a magnifying factor of one or greater provided the single best enhancement and display technique for mapping inland valley bottoms (see illustrations in figures 4, 5 and 11). A combination of this technique with two other image enhancement techniques, involving a false colour composite (FCC) of TM4 (red), TM3 (green) and TM5 (blue) and a ratio RGB (red-green-blue) image of TM4/TM5, TM4/TM3 and TM4/TM1, improved the results significantly. Relative to 1 : 200000 topographic maps TM data mapped up to 118 per cent stream frequencies (number of streams km^?2) and 99 per cent stream densities (length of streams km^?2). However, relative to 1 : 50000 topographic maps TM data mapped only 74 per cent stream frequencies and 77 per cent stream densities. The ability of TM data to provide the shape, size, area, spatial distribution and land use characteristics of inland valleys (see figure 11, for example), unlike other data sources, such as topographic maps, have been highlighted in this paper. TM-derived valley bottom widths and vegetation characteristics (e.g., Ratio Vegetation Index; RVI) of valley bottoms and valley fringes provided highly positive correlations or formed statistically significant relationships with the corresponding ground-measured information. In the total study area of 3.12 × 10⁶ha, covered by a full Landsat-5 TM scene (image), there were 9 per cent valley bottoms (see figure 11) and 192 per cent valley fringes as mapped using the espoused methodology. Of this, 7.9 per cent of the valley bottoms and 159 per cent of the valley fringes were cultivated. The percentage of inland valleys and their cultivation intensities relative to their distance from the road network and settlements were established. The major road network and a significant proportion of the settlements were also mapped directly from the TM data. These results indicate the strength of the methodology to rapidly map and characterize inland valley agroecosystems at regional level using high-resolution remotely sensed data.     

Assessment of atmospheric correction methods for Landsat TM data applicable to Amazon basin LBA research

Atmospheric correction is an important preprocessing step required in many remote sensing applications. The authors are engaged in the project 'Human Dimensions of Amazonia: Forest Regeneration and Landscape Structure' in NASA/INPE's Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) programme. This project requires use of corrected Landsat TM data since research foci integrate ground-based data and TM to: (1) measure and model biomass; (2) classify multiple stages of secondary succession; (3) model land cover/land use changes; and (4) derive spectral signatures consistent across different study areas. The 30+ scenes of TM data are historic and lack detailed atmospheric data needed by physically-based atmospheric correction models such as 6S (Second Simulation of the Satellite Signal in the Solar Spectrum). Imagebased DOS models are based on image measurements and explored in this article for application to LBA study areas. Two methods using theoretical spectral radiance and image acquisition date respectively were used to convert TM DN values to at-satellite radiance. Three image-based models were employed using each method to convert at-satellite radiance to surface reflectance. Analyses of these six different image-based models were conducted. The Improved Imagebased DOS was the best technique for correcting atmospheric effects in this LBA research with results similar to those obtained from physically-based approaches.     

A comparison of SPOT and Landsat-TM data for use in conducting inventories of forest resources

Abstract

SPOT multispectral (XS) and Landsat Thematic Mapper (TM) digital data were studied in an attempt to evaluate the use of this data in detailed assessments of forest conditions. Forest type, basal area, and age class information were collected from 256 sample sites within an intensively managed 80000acre experimental forest in North Carolina, U.S.A. A comparison of the SPOT and TM data with the sample site information showed that XS3, the near-infrared waveband, and TM bands 2, 3, 4, 5, and 7 were significantly correlated with basal area. Age class was not found to be significantly correlated with any of the three SPOT XS wavebands. TM bands 2, 3, 4, 5, and 7 were, however, shown to be significantly correlated with age class. Although significant, the correlation coefficients between the TM or SPOT waveband data and basal area or age class were low (<0.65).

Six forest cover types, and an additional water category, were selected as the basis of a land cover classification system for use with the TM and SPOT data. Verification of the classification of the seven cover types using the SPOT XS waveband data resulted in an estimated accuracy of 74.4 per cent. Classification accuracy was slightly reduced (70.8 per cent) when the TM wavebands corresponding to the SPOT XS bands were used as inputs to the classifier. When each of the six visible and reflective infrared TM wavebands were included in the classification process overall accuracy increased to 885 per cent.     

Optimal Landsat TM band combinations and vegetation indices for discrimination of six grassland types in eastern Kansas

Hyperspectral sensors can make narrow-band measurements for several hundred regions of the electromagnetic spectrum, and with increasing frequency, multi-dates of remotely sensed data are being used for Earth observation purposes. The use of more spectral bands is creating greater demand for larger computer storage capacity and faster data processors. This study evaluates the use of raw Thematic Mapper (TM) band combinations and several derived vegetation indices to determine optimal vegetation indices and band combinations for discriminating among six grassland management practices in eastern Kansas. Results showed that among the transformed dataset, the Greenness Vegetation Index was found to be the best for discriminating among grassland management types. When evaluating the raw TM bands, TM4 (NIR) was always selected in Discriminate Analysis as the best discriminating variable. There is no significant improvement in grassland discrimination by using a combination of the raw TM bands and the vegetation indices. Increasing the number of TM bands by using multiple dates of imagery will improve discrimination accuracy up to a point, but the use of too many bands (greater than 10 or 12) can actually decrease discrimination accuracy.     

Multi-temporal remote sensing study of spectral signatures of crops in the Thessaloniki test site

Abstract

In the framework of a pilot project of the Commission of the European Community concerning the application of remote sensing techniques for agricultural statistics, a specific study of an area in Northern Greece is being carried out at the Joint Research Centre, Ispra. This study involves the use of multi-temporal TM and SPOT data, in order to combine the spatial resolution of SPOT with the spectral resolution of TM and to gain in flexibility for the choice of dates. This approach is expected to overcome ambiguities in the spectral definition of crops, but significant problems are introduced, due mainly to the different atmospheric conditions present at the various dates. A study of the effect of the various factors on the spectral response of the crops will help to define a classification criterion based on their phenological variation.