Terrascope is a Google Earth implementation of the LANDSAT MSS, TM and ETM+ ortho mosaics for the 1970s, circa 1990 and circa 2000. It is designed to allow rapid comparison of LANDSAT imagery between these periods for any view in Google Earth. The imagery is provided as superoverlays in which resolution (level of detail) increase as you zoom in on an area. Full resolution is 57 metres/pixel for the 1970's (MSS), 28.5 metres/pixel for the circa 1990 (TM) and 14.25 metres/pixel for circa 2000 (ETM+). The rationale for terrascope is to provide an easy mechanism for visual change detection for non remote-sensing specialists who may be interested in environmental change research (desertification, land use change, urbanisation, coastal fluvial and water body change), awareness raising (of hotspots for habitat loss for example), and conservation monitoring or prioritisation uses. <P>
Terrascope in Google Earth
Terrascope brings some history to Google Earth. Google Earth imagery is largely made up of the NASA Circa 2000 LANDSAT Mosaic (processed very well by TerraMetrics) with Digital Globe and other higher resolution imagery (largely post-2000 in origin) added for large parts of Europe and the US and for cities and other areas of interest across much of the rest of the world. We have added the public domain LANDSAT MSS Mosaic (circa 1975) and the LANDSAT TM Mosaic (1990) for most of the world. We are also running the LANDSAT 2000 Mosaic and adding that for parts of the world so that - as Google update their imagery - the following history will be visible : (all circa) 1975, 1990, 2000 and Google native (post 2000). The aim is to help visualise land cover change in a simple way. The images have been converted to 'natural' colour. Invariably the data quality and resolution are reduced as we go back in time and some parts of the globe are missing for various reasons, including the degradation of data storage media at the LANDSAT stations, but nevertheless a useful simple visiualisation is possible. Click the link and when Google Earth opens up zoom in to the area of your interest (best to start within the tropics). The 1990 layer will start to load once you get close enough. Zoom in for full resolution. Use the slider to compare with the Google native imagery underneath.
There are also layers for coverage of the different datasets and metadata (image names and dates of capture for the individual LANDSAT images) for the 1990 layer. Activate the 1990 metadata layer and zoom in for the placemarks if you want to see the metadata. This is very much a work in progress.
If you see any interesting land cover history then use the built-in GEOWIKI to tell others about it.
Terrascope in Google Earth