The GeoBase Orthoimages 2005-2010 are Spot 4 and Spot 5 raster data and comprise five spectral bands: one panchromatic band with a pixel size of 10 m, and four multispectral bands with a pixel size of 20 m. The orthoimages are produced in accordance with the 1983 North American Reference System (NAD83SCRS) using the Universal Transverse Mercator (UTM) and Lambert Conformal Conic (LCC) projections. Each GeoBase Orthoimage 2005-2010 covers an area of approximately 3 600 km2, or 60 km x 60 km of the Earth's surface.
All orthoimages are created with the most accurate control data available at the time. Various sources of planimetric data are used to rectify the images, and priority is given to the most accurate sources. The priority of sources used is established according to the following order: The Control Points for Landsat 7 Imagery, Canada, Level 1 (PCILC1), the National Road Network (NRN) and lastly, the Landsat 7 Orthorectified Imagery over Canada.
The CDED (Canadian Digital Elevation Data) was also used to orthorectify the images. The most precise CDED are given priority. The majority of the data is extracted from the GeoBase portal, except for those areas of Quebec that are south of the 49th parallel, for which provincial data was used.
The accuracy is evaluated for each data set of orthoimages. The control data, which is extracted from the aforementioned sources, is comprised of road intersection vector data and lake/island centroids. In some cases, the intersection of the centre line of a surficial river is used. The control points are evenly distributed within the image in specific sectors.
The GeoBase Orthoimages 2005-2010 are made available to the public as soon as they are produced. The production of orthoimages depends on the availability of control information at the origin and the ability of the producing organization to generate them.
