Multispectral Scanner Scenes Research Articles

Mapping lichen changes in the summer range of the George River Caribou Herd (Québec-Labrador, Canada) using Landsat imagery (1976-1998)

Habitat studies are essential in order to understand the dynamics of migratory caribou herds and to better define management strategies. In this paper, multi-date Landsat images are used to map lichen in the summer range of the George River Caribou Herd (GRCH), Québec-Labrador (Canada), over the period from 1976 to 1998. Multi-Spectral Scanner scenes from the seventies and Thematic Mapper scenes from the eighties and nineties were radiometrically normalized and processed using spectral mixture analysis to produce lichen fraction maps and lichen change maps. Field sites, surveyed during summer campaigns in 2000 and 2001, are used to validate the lichen maps. Results show a good agreement between field data and the lichen results obtained from image analysis. Maps are then interpreted in the context of previous caribou dynamics and habitat studies conducted in the study area over the last three decades. The remote-sensing results confirm the habitat degradation and herd distribution patterns described by other investigators. The period between 1976-1979 and 1985-1986 is characterized by a localized decrease in lichen cover in the southern part of the study area, whereas from 1985-1986 to 1998 the decrease in lichen cover extends northward and westward. This period coincides with the widest extent of the GRCH summer range and activity. The approach presented in this paper provides a valuable means for better understanding the spatio-temporal relation between herd dynamics and distribution, as well as habitat use. Satellite remote sensing imagery is a useful data source, providing timely information over vast and remote territories where caribou populations cannot be surveyed and managed on a frequent basis.

An analysis of land cover changes in the Northern Forest of New England using multitemporal Landsat MSS data

Landsat Multispectral Scanner (MSS) data were used to characterize land cover types, land cover changes, and landscape patterns in the Northern Forest region of Vermont, New Hampshire, and western Maine, USA. Eight Landsat MSS scenes from 1973, 1978, 1984/85, and 1990/91 were used to cover the regional study area and 18-year time period. Four watershed segments within the Northern Forest area were analysed: the Lamoille River watershed (151814 ha), the Connecticut River watershed (706880 ha), the Androscoggin River watershed (655445 ha), and the Kennebec River watershed (457168 ha). Multitemporal analysis indicates that the percentage of forested land that was converted to open land in each watershed over the 18-year period is similar, and is estimated to be approximately 10% of the forested land in each watershed segment.

Subpixel forest cover in central Africa from multisensor, multitemporal data

Seven Landsat Multispectral Scanner (MSS) scenes in central Africa were coregistered with 8 km resolution data from the 1987 AVHRR Pathfinder Land data set. Percent forest cover in each 8 km grid cell was derived from the classified MSS scenes. Linear relationships between percent forest cover and 30 multitemporal metrics derived from all AVHRR optical and thermal channels were determined. Correlations were strongest for the mean annual normalized difference vegetation index (NDVI) and mean annual brightness temperature (AVHRR Channel 3) and weakest for those metrics, besides NDVI, based on near-infrared reflectances (AVHRR Channel 2). The relationships were used to estimate percent forest cover in various locations in the study area using multiple linear regression and regression trees. Overall, the multiple linear regression provided more accurate results. Predicted percent forest cover estimates were within 20% of the “actual” percent forest cover (derived from the MSS data) for approximately 90% of the grid cells. The RMS error for the prediction was 12% forest cover. RMS errors above 18% forest cover were obtained when using AVHRR data from a single month to derive predictive relationships. The results demonstrate that multitemporal data reflecting vegetation phenology can be used to estimate subpixel forest cover at coarse spatial resolutions.

Techniques for Computer-Assisted Mapping of Rangeland Change

Management of grasslands subject to replacement by woody species requires an understanding of the scales and patterns of change and how to detect and express them. We used the Jornada del Muerto Basin of southern New Mexico as a case study, testing the suitability of Landsat Multi-Spectral Scanner (MSS) data for detecting vegetation changes. Cycles of drought and heavy grazing have apparently changed the once extensive grasslands of the upland Jornada and surrounding areas gradually into a patchwork of shrublands and relict grasslands. Integrated remote sensing and geographic information system (GIS) techniques can facilitate automated detection of these rangeland changes. A GIS was used to store and process two 4-band, co-registered multi-temporal Landsat MSS scenes collected in July 1983 and August 1992. Scene-to-scene radiometric calibration was performed using a regression technique. The data were then evaluated for changes 3 different ways using algorithms based on differences between the 'red' (chlorophyll absorption) bands for the 2 scenes; the Euclidean distances between the 'red' and 'near-infrared' bands for the 2 scenes; and a standardized principal components analysis using all 8 MSS bands. A threshold of 3 standard deviations above the mean was applied to each of the 3 resulting 'change' images to represent areas of extreme change. Correlations among these images ranged between 0.83 and 0.95. We conclude these techniques can identify successfully the patterns and extent of extreme change, and thus have potential value for management of our rangelands resources.

Using landsat multispectral scanner data to estimate suspended sediments in Moon Lake, Mississippi

Suspended sediments are a major factor affecting water quality in many aquatic ecosystems. Research was undertaken to determine the application of digital spectral data collected by the multispectral scanner (MSS) on the Landsat satellite for estimating suspended sediments in aquatic ecosystems where mean annual concentrations of suspended sediments are greater than 50 mg L −1. Digital spectral data from 14 Landsat MSS scenes of Moon Lake in Coahoma County, Mississippi were analyzed and compared with ground measurements of total solids and suspended sediments in the lake surface water for the period between January 1983 and May 1985. Coefficients of determination ( R 2) greater than 0.81 were calculated between MSS Band 2 (0.6–0.7 μm) or Band 3 (0.7–0.8 μm) and suspended sediments or total solids. Coefficients of determination for multiple regression using three or four MSS bands were greater than 0.90. This study showed that digital spectral data from the Landsat satellites can be used to locate and monitor surface-suspended sediments in aquatic ecosystems. With such a digital computer technique, entire regions can be surveyed quickly to locate aquatic ecosystems with suspended sediment problems. Conservation efforts can then be concentrated on those aquatic ecosystems with the most serious suspended sediment problems and soil conservation strategies developed in their watersheds to control erosion and sediment yield and thus to improve water quality.

Comparison of Landsat Multispectral Scanner and Thematic Mapper Radiometric and Spatial Characteristics Over Glaciers (Abstract)

For more than 10 years, images obtained from the four Landsat Multispectral Scanner (MSS) bands have provided important data for mapping and glaciological studies in the inaccessible polar regions. During this period, the specifications of the MSS have remained little altered, to allow data comparability. More recently, satellites 4 and 5 of the Landsat series have been equipped additionally with Thematic Mapper (TM) sensors. The TM has 7 bands in the visible, near infra-red, mid infra-red, and thermal infra-red, together with a larger dynamic range and improved spatial resolution relative to the MSS. The aim of this paper is to compare MSS and TM computer-compatible tapes (CCTs) from a glacierized area in order to demonstrate the advantages of using TM data in glaciological applications. The digital MSS and TM scenes compared were imaged simultaneously from Landsat 5 on 5 May 1984 over the north-west part of Spitsbergen, Svalbard (path 218, row 3). This location was selected because of the range of glaciological features present: numerous valley glaciers, the ice field of Holtedahlfonna, fast ice, and ice floes. Partially cloud-covered imagery was preferred, to allow comparison of the two sensors in terms of their ability to distinguish between clouds and snow. The time of year is also advantageous, in that Sun elevation (27°) is high enough for detector saturation to occur in MSS band 2 (Dowdeswell and McIntyre 1986). Surface-elevation data from airborne radio echo-sounding, and other ancilliary glaciological information, are also available for this part of Svalbard. Differences in the dynamic range and the wavelengths over which TM and MSS data are collected have two main implications for glaciological studies. First, snow and snow-covered ice masses can be distinguished easily from cloud cover in TM band 5 (1.57 to 1.78 μm). Snow appears dark whereas clouds are light at this wavelength. For example, thin clouds over part of Oscar II Land in Spitsbergen became apparent. In many MSS scenes of the Antarctic, the cloud-free ice-sheet surface has been misidentified as cloud-covered during quality-control analysis. Secondly, the wider dynamic range of the TM sensors means that saturation occurs less frequently over snow than was the case with MSS imagery. Digital analysis of MSS and TM scene radiance over Spitsbergen demonstrates this fact and implies that ice-surface topographic information will only rarely be degraded in TM imagery, although TM band 1 (0.45 to 0.52 μm) is most often saturated. The nominal spatial resolution of TM sensors is 30 m, except for the thermal infra-red band. This is a significant improvement over the 79 m by 56 m resolution of the MSS. A major advantage of this is that ice margins and ice-surface features can be more precisely identified. More accurate glacier maps can be made, and smaller variations in termini positions of outlet glaciers can be monitored. Ice-surface features, such as crevasses, are more likely to be recorded on TM imagery, and examples are shown from Spitsbergen glaciers. The identification of such features is of major importance in studies of ice-surface velocities from Landsat imagery. For sea-ice applications, the ability to identify smaller floes is also important; for example, in the analysis of floe-size distributions. The only significant drawbacks to the use of Landsat TM data in glaciological studies are the expense, particularly in the more useful digital format, and the small amount of coverage yet available for the polar regions.

Comparison of Landsat Multispectral Scanner and Thematic Mapper Radiometric and Spatial Characteristics Over Glaciers (Abstract)

For more than 10 years, images obtained from the four Landsat Multispectral Scanner (MSS) bands have provided important data for mapping and glaciological studies in the inaccessible polar regions. During this period, the specifications of the MSS have remained little altered, to allow data comparability. More recently, satellites 4 and 5 of the Landsat series have been equipped additionally with Thematic Mapper (TM) sensors. The TM has 7 bands in the visible, near infra-red, mid infra-red, and thermal infra-red, together with a larger dynamic range and improved spatial resolution relative to the MSS. The aim of this paper is to compare MSS and TM computer-compatible tapes (CCTs) from a glacierized area in order to demonstrate the advantages of using TM data in glaciological applications.The digital MSS and TM scenes compared were imaged simultaneously from Landsat 5 on 5 May 1984 over the north-west part of Spitsbergen, Svalbard (path 218, row 3). This location was selected because of the range of glaciological features present: numerous valley glaciers, the ice field of Holtedahlfonna, fast ice, and ice floes. Partially cloud-covered imagery was preferred, to allow comparison of the two sensors in terms of their ability to distinguish between clouds and snow. The time of year is also advantageous, in that Sun elevation (27°) is high enough for detector saturation to occur in MSS band 2 (Dowdeswell and McIntyre 1986). Surface-elevation data from airborne radio echo-sounding, and other ancilliary glaciological information, are also available for this part of Svalbard.Differences in the dynamic range and the wavelengths over which TM and MSS data are collected have two main implications for glaciological studies. First, snow and snow-covered ice masses can be distinguished easily from cloud cover in TM band 5 (1.57 to 1.78 μm). Snow appears dark whereas clouds are light at this wavelength. For example, thin clouds over part of Oscar II Land in Spitsbergen became apparent. In many MSS scenes of the Antarctic, the cloud-free ice-sheet surface has been misidentified as cloud-covered during quality-control analysis. Secondly, the wider dynamic range of the TM sensors means that saturation occurs less frequently over snow than was the case with MSS imagery. Digital analysis of MSS and TM scene radiance over Spitsbergen demonstrates this fact and implies that ice-surface topographic information will only rarely be degraded in TM imagery, although TM band 1 (0.45 to 0.52 μm) is most often saturated.The nominal spatial resolution of TM sensors is 30 m, except for the thermal infra-red band. This is a significant improvement over the 79 m by 56 m resolution of the MSS. A major advantage of this is that ice margins and ice-surface features can be more precisely identified. More accurate glacier maps can be made, and smaller variations in termini positions of outlet glaciers can be monitored. Ice-surface features, such as crevasses, are more likely to be recorded on TM imagery, and examples are shown from Spitsbergen glaciers. The identification of such features is of major importance in studies of ice-surface velocities from Landsat imagery. For sea-ice applications, the ability to identify smaller floes is also important; for example, in the analysis of floe-size distributions.The only significant drawbacks to the use of Landsat TM data in glaciological studies are the expense, particularly in the more useful digital format, and the small amount of coverage yet available for the polar regions.

The Surface Topography of Large Ice Masses from Landsat Imagery

AbstractApparent ice-surface topography is observed at several scales on Landsat multi-spectral scanner (MSS) imagery. Digitally enhanced MSS scenes from Antarctica and Nordaustlandet, Svalbard, are compared with ice-surface elevations from aircraft altimetry (relative accuracy 2–3 m) to show that this apparent topography is real. Apparent ice divides on Landsat images fit closely with divides on altimetric records. Ice-surface irregularities within drainage basins are also shown to be real. On Byrd Glacier, Antarctica, apparent “flow lines” coincide with ridges on altimetric records. Synoptic Landsat data, calibrated by information from aircraft altimetric flight lines, are used to classify the surface roughness of the ice caps on Nordaustlandet and 40% of the Antarctic ice sheet. On Nordaustlandet, the roughest ice is of amplitude 15–25 m and wavelength 3–4.5 km. Drainage basins with such rough surface characteristics may be associated with ice streams or possibly past surge activity. The most rough Antarctic terrain is up to 60 m in amplitude, with wavelengths of <10 km. The roughness of the Antarctic ice sheet increases with distance from ice divides, reflecting changes in the parameters affecting the transfer of basal stresses to the ice surface.

The Surface Topography of Large Ice Masses from Landsat Imagery

AbstractApparent ice-surface topography is observed at several scales on Landsat multi-spectral scanner (MSS) imagery. Digitally enhanced MSS scenes from Antarctica and Nordaustlandet, Svalbard, are compared with ice-surface elevations from aircraft altimetry (relative accuracy 2–3 m) to show that this apparent topography is real. Apparent ice divides on Landsat images fit closely with divides on altimetric records. Ice-surface irregularities within drainage basins are also shown to be real. On Byrd Glacier, Antarctica, apparent “flow lines” coincide with ridges on altimetric records. Synoptic Landsat data, calibrated by information from aircraft altimetric flight lines, are used to classify the surface roughness of the ice caps on Nordaustlandet and 40% of the Antarctic ice sheet. On Nordaustlandet, the roughest ice is of amplitude 15–25 m and wavelength 3–4.5 km. Drainage basins with such rough surface characteristics may be associated with ice streams or possibly past surge activity. The most rough Antarctic terrain is up to 60 m in amplitude, with wavelengths of <10 km. The roughness of the Antarctic ice sheet increases with distance from ice divides, reflecting changes in the parameters affecting the transfer of basal stresses to the ice surface.

Assessment of Landsat Multispectral Scanner spectral indexes for monitoring arid rangeland

The utility of Landsat Multispectral Scanner (MSS) spectral indexes for monitoring arid range land was tested in south-central New Mexico by determining correlations between spectral indexes and vegetation parameters. Also, spectral index change from 1976 to 1980 was calculated from retrospective MSS data and compared with qualitative ground truth to determine if vegetation change could be detected using spectral indexes. MSS band 5, albedo, and the Kauth-Thomas Brightness component were correlated with total vegetation cover, with maximum r = −0.844. Dry season green vegetation indexes were the best estimators of combined cover of mesquite plus snakeweed, two shrub invaders of degraded grassland. The dry season-wet season difference in green vegetation indexes gave rough estimates of grass cover. In retrospective monitoring, cover change in response to shrub control and changes in grating intensity and rainfall was detected by change in brightness indexes. Brightness index change consistently differentiated between cover increase and decrease, but Index change was apparently offset from true cover change. The offset was attributed, at least in part, to failure of the methods used to standardize MSS scenes for differences in sensor response. In contrast to brightness indexes, green vegetation indexes failed to consistently differentiate between cover increase and decrease.