Armand LaRocque

Surficial materials mapping in Nunavut, Canada with multibeam RADARSAT-2 dual-polarization C-HH and C-HV, LANDSAT-7 ETM, and DEM data

Our study assesses the use of multibeam RADARSAT-2 dual-polarization C-HH and C-HV, LANDSAT-7 ETM+, and Digital Elevation Model (DEM) data for mapping surficial materials in Nunavut, Canada. The RADARSAT-2 images were acquired using standard beam 1 and 7 modes in both ascending and descending orbits. RADARSAT-2 images were filtered to reduce speckle and then orthorectified. Representative training areas of distinct surficial deposits (bedrock, boulders, organic deposits, sand and gravel, thick till with dense vegetation, thick till with sparse vegetation, and thin till) were identified from field information and by interpreting panchromatic aerial photographs and LANDSAT-7 ETM+ images. Maximum likelihood supervised classifications were conducted on the RADARSAT-2 C-HH and C-HV images, individually and combined with LANDSAT-7 ETM+ and (or) DEM data. The best overall classification accuracy was obtained by combining RADARSAT-2 C-HH and C-HV images with LANDSAT-7 ETM+ and DEM data. Confusion between several surface materials was reduced, but confusion between “bedrock” and “boulders” and between “sand and gravel” and “organic deposits” or “thin till” class still remains. Another limitation of the study includes the lack of a field survey to validate training areas for three of the four detailed analysis areas. Nonetheless, this study produced surficial materials maps covering eight 1:250000 scale National Topographic System of Canada sheets that provide important geological information about this remote area.

Characteristics of late-glacial ice-dammed lakes reconstructed in the Appalachians of southern Québec

Abstract During deglaciation, several valleys of the Appalachians of southern Quebec were affected by the pounding of ice-dammed lakes. More than 300 water planes were reconstructed in the southeastern part of the region with the methodology presented elsewhere in this volume (Quat. Int. (2002) this volume). Their characteristics during deglaciation gradually changed, following four main steps: (1) ice-dammed ponds; (2) ice-dammed lakelets; (3) intermediate lakes; and (4) large ice-dammed lake. These various lake types differed by the size, the shape, the position of the spillway and the depth of the former ice-dammed lake as well as by the relative duration and by the stability degree of each lake level. In this study, a relative duration of each reconstructed lake level was determined using the distance covered by the retreating ice margin during the former existence of the water body. The stability of the water level also explained the difference in the degree of development of shoreline features among water bodies with relatively similar sizes.

Effects of incidence angles and image combinations on mapping accuracy of surficial materials in the Umiujalik Lake area, Nunavut, using RADARSAT-2 polarimetric and LANDSAT-7 images, and DEM data. Part 1. Nonpolarimetric analysis

This study assesses the use of multibeam RADARSAT-2 multipolarized synthetic aperture radar images (hereafter termed “RADARSAT-2 images”), in combination with LANDSAT-7 Enhanced Thematic Mapper (ETM +) and digital elevation model (DEM) data for mapping surficial materials (bedrock, boulders, organic material, sand and gravel, thick till, and thin till) in Arctic Canada. In particular we tested the effects of RADARSAT-2 incidence angles on classification accuracy. This research contributes to the geoscience framework for mineral exploration in Archean to Paleoproterozoic rocks of the northeast Thelon region of Nunavut. The RADARSAT-2 images were acquired in three west-looking descending beam modes (FQ1, FQ12, and FQ20) with increasing respective incidence angles. A maximum likelihood classification (MLC) was applied to different combinations of RADARSAT-2 and LANDSAT-7 ETM+ images, and DEM data. The incidence angle effect on classification overall accuracies is greatest when only the HH polarized images are used, but is reduced when the HV and (or) VV polarized images are added to the classifier. The best MLC overall accuracy of 85.1% is achieved by combining all polarizations and all incidence angles (beam modes) with LANDSAT-7 ETM+ images and DEM data. The influences of variable environmental conditions (moisture and temperature) on mapping accuracy require further research.

Modelling and mapping permafrost at high spatial resolution using Landsat and Radarsat-2 images in Northern Ontario, Canada: Part 2 – regional mapping

Permafrost occurs mainly at high latitudes and is currently subjected to widespread thawing due to global warming, which has significant ecological and socio-economic impacts. One way to map permafrost condition and its change at high spatial resolution is to calculate soil temperatures using a process-based permafrost model, such as the Northern Ecosystem Soil Temperature (NEST) model, based on remote-sensing data. In a previous paper (Ou et al. 2015), we showed that the NEST model can be used to model soil temperatures, frozen depth, and active layer thickness in a warm and discontinuous permafrost area that is located in the Hudson Bay Lowlands in northern Ontario, Canada. In this article, we applied the model over the whole study area to map the distribution of permafrost conditions and their changes from the 1960s to the 2000s at high spatial resolution. Some of the model inputs were estimated based on land-cover and surficial material maps derived from Landsat-5 TM and Radarsat-2 SAR C-HH and C-HV images. By comparison to field observations, we were able to achieve an average mapping accuracy of 99% for both the land-cover and surficial material maps, when both Landsat and Radarsat-2 images were used. In addition, all the 49 field-observed treed and shrub permafrost landform sites found in the study area were correctly identified on the classified image. This spatial modelling study shows that permafrost currently underlies about 9.4% of the land in this area, and varies significantly among land-cover types. With the increases in mean annual air temperature (1.9°C) and precipitation (2.4%) from the 1960s to the 2000s, the model results show a deepening of active layer by 20.5%. However, the permafrost has persisted in most of the area due to the protection of thick peat. The modelled permafrost extent reduced only from 9.8% to 9.4%.

Modelling and mapping permafrost at high spatial resolution using Landsat and Radarsat images in northern Ontario, Canada: part 1 – model calibration

Permafrost is an important ground thermal condition that has significant biophysical and socio-economic impacts. In order to better understand the distribution and dynamics of permafrost, there is a need to map permafrost at high spatial resolution. This study is part of a research project that aims to model and map permafrost using remote sensing images and the Northern Ecosystem Soil Temperature (NEST) model in the central part of the Hudson Bay Lowland in northern Ontario, Canada. The study area is near the southern margin of permafrost region where permafrost exists only in isolated patches. In this study, we ran the NEST model from 1932 to 2012 using a climate data set compiled from station observations and grid data sources. The model outputs were then compared to field observations acquired during 2009–2012 at seven peat monitoring stations and two flux towers, which represent three major types of peatland in the study area (bog, fen, and palsa). The simulated soil temperatures at various depths show good agreement with the observations, and the simulated latent and sensible heat fluxes and net radiation are similar to the observations at the two flux towers. The model accurately shows the existence of permafrost only at palsa sites. Based on the general range of climate and ground conditions in this area, sensitivity tests indicate that the modelled permafrost conditions are sensitive to leaf area index, air temperature, precipitation, and soil texture. Therefore, the NEST model is capable of simulating ground temperature and permafrost conditions in where permafrost occurs only sporadically. A companion paper (part 2) uses the model with Landsat and Radarsat imagery to map the distribution and dynamics of permafrost in this area.

A methodology to reconstruct small and short-lived ice-dammed lakes in the Appalachians of Southern Québec

Abstract Previous studies on the deglaciation of the Appalachians of southern Quebec reconstructed only the most extensive ice-dammed lakes and the most stable glaciolacustrine water levels. They only used the best developed shoreline features, and thus were not able to reconstruct small or short-lived ice-dammed lakes, both being characterized by a weak development of their features. We propose a methodology to reconstruct glacial lakes which follows three main steps: (1) the mapping of shoreline features, generally the best developed ones, as in previous studies; (2) the delineation of the former shoreline for each water level, by also considering the less well-developed shoreline features which were found during field surveys designed as a function of the presumed shoreline position; and (3) the mapping of the maximum extension of the water plane, which includes the location of the former ice dam and of the former glacial lake spillway. In southern Quebec, small ice-dammed lakes were numerous and important because they shaped the geomorphology of the region during the deglaciation. They are thus among the key components of a deglaciation model for this area.

Effects of incidence angles on mapping accuracy of surficial materials in the Umiujalik Lake area, Nunavut, using RADARSAT-2 polarimetric SAR images. Part 2. Polarimetric analysis

Our study assesses the effect of incidence angle on classifications obtained using various polarimetric classifiers applied to polarimetric RADARSAT-2 synthetic aperature radar (SAR) images for mapping surficial materials in Arctic Canada. The RADARSAT-2 polarimetric SAR images were acquired over the Umiujalik Lake test area of Nunavut in three west-looking descending beam modes (FQ1, FQ12, and FQ20) with increasing respective incidence angles. Polarimetric analyses included computation of polarimetric signatures, Wishart supervised classification, as well as Wishart–H/ , Wishart–H/ /A, and Freeman–Wishart unsupervised classifications. Polarimetric signatures helped to understand class separability as a function of the scattering mechanisms of the surficial materials considered in this study. The medium incidence angle (FQ12) image produced the best overall classification accuracy (48.7%) for the Wishart supervised classification. In general, the Freeman–Wishart unsupervised classification produced better areal distribution of surficial materials with the FQ12 and FQ20 images than with the steep angle FQ1 image. More sophisticated classification algorithms are required to combine the multibeam RADARSAT-2 polarimetric SAR images with other geospatial data such as optical images and digital elevation model data. The influences of variable environmental conditions (moisture and temperature) on mapping accuracy of surficial materials also require further research.

Use of Radarsat-2 and ALOS-PALSAR SAR images for wetland mapping in New Brunswick

Our study tests the use of dual-polarized (HH, HV) RADARSAT-2 C-band and ALOS-PALSAR L-band SAR images for mapping wetland areas in New Brunswick. The study also uses LANDSAT-5 TM and DEM data. The resulting maps were compared to GPS field data as well as to two wetland maps currently in use by the Province of New Brunswick. Overall the Random Forests classifier gave better classification accuracies than the maximum likelihood classifier. The comparison with the 146 wetland truth sites shows that 73.3% are correctly identified over the LANDSAT-5 TM classified image. For the SAR-based classified images, the number of correctly identified wetland ground truth sites is higher when the image acquired during the flooding is considered, the difference being higher with the ALOS-PALSAR images than with the RADARSAT-2 images. The number of correctly identified sites is the highest when both the ALOS-PALSAR images and RADARSAT-2 images are used (98.6%). These percentages of correctly identified wetland sites are well above of those computed using the DNR wetland and forested wetland maps (44.5 %).

Model calibration for mapping permafrost using Landsat-5 TM and RADARSAT-2 images

Permafrost is an important ground condition in high latitudes. Climate warming may lead to thickening of active layer, reducing permafrost thickness and extent, melting ground ice, causing ground subsidence and thermokarst erosions. In order to better map the distribution and dynamics of permafrost, there is a need to develop and test permafrost models that can be used with high spatial resolution remote sensing data. The purpose of this study is to calibrate the Northern Ecosystem Soil Temperature (NEST) model over the Victor Mine area located in the Hudson Bay Lowlands, Northern Ontario, Canada. The area is near the southern margin of permafrost region where permafrost exists only in isolated patches. We estimated and calibrated model input parameters using data from 1932 to 2012. The outputs were compared to field observations acquired between 2009 and 2012 at seven peat monitoring stations and two flux towers. Simulated soil temperatures show good agreement with observations at various depths for the different peatland types. The model shows the existence of permafrost only at palsa sites, which is in agreement with field observations. The calibrated model will be used to map permafrost over the whole area using remote sensing images.

New ways of teaching remote sensing and high school curricula: Online delivery of courses

Our study compared the traditional method of teaching remote sensing with a new method that use teaching platform and Internet. We showed that the new teaching method has more advantages than the traditional one. In addition, the paper presented three lectures that can be used to teach not only geography but also mathematics high school curricula.