1. Change Analysis of Glacial Retreat Using Landsat Data and GIS Image Processing: Lloyd George Icefield, Northeast British Columbia, Canada. Chad Seigel, Oil and Gas Commission, Mile 301 Alaska Highway, Fort Nelson, British Columbia, Canada V0C 1R0 (chad.seigel@gov.bc.ca) Abstract Northeast British Columbia is characterized by the low relief Alberta Plateau which is flanked to the west by the Northern Rocky Mountains. The Northern Rockies contain several glaciers and small icefields, of which the Lloyd George Icefield is the largest. Recent changes in global climate have caused glaciers to advance and retreat over the past several decades at various rates. Landsat imagery is a valuable tool when used to detect change in glacier area cover, and even more valuable in extremely remote areas which are difficult to access such as The Northern Rockies. This poster presents a comparison of Landsat MSS and ETM+ images from 1975 and 2001, of the Lloyd George Icefield in NortheastBritish Columbia. These two images were analysed to determine if there had been any change in area covered by the icefield over the 26 years spanned by the datasets. Landsat data has proven to be far superior to conventional maps and aerial photography for accurately identifying and mapping change in terms of glacial cover. This technology will become more valuable in the future, as the library of satellite images keeps growing, and more data becomes available to study glacial change giving scientists more insight into problems associated with global climate change. Overview Map Surface area of the Lloyd George Icefield was 69km2 in 2001. Surface area of the Lloyd George Icefield was 75km2 in 1975. Surface Area Maps Landsat 7 ETM+ 3,4,5 composite of the Lloyd George Icefield. Landsat 2 MSS 1,3,4 composite of the Lloyd George Icefield. False Colour Composite Images Ratio Images 2/3 ratio provides best ice delineation with the MSS image. 3/5 ratio provides best ice delineation with the ETM+ image. Summary of processing procedures Both datasets were first looked at to determine if haze correction was necessary, which was not required as the scenes were very clear with minimum values of zero. Georeferencing of the dataset had already been completed by the Global Land Cover Facility at the University of Maryland from where the images were acquired. Next a sub scene was WINDOWed out of the original scene using UTM coordinates for the corners of the new sub scene. The 1975 data set which was acquired by Landsat 2 first had to be resampled to match the resolution of the 2001 Landsat 7 dataset. Once this was completed OVERLAY images were created for each dataset. From the overlay images RECLASS was run to create Boolean images with the value one for ice and zero for surrounding areas. GROUP was then run to group cells of the same value into contiguous groups with unique identification numbers. Groups which made up the Lloyd George Icefield were selected and placed into an attribute values file. Care was taken when selecting these groups so the same groups were used in creating both the 1975 and 2001 images to avoid introduction of bias. ASSIGN was then run with the attribute values files in order to give values of one for ice, and a value of zero for surrounding areas. This image was then run through AREA to determine the area of the icefield. The area of the icefield in 1975 was 75 Km2, and in 2001 it was 69 Km2.