Satellite Imagery - Definition of terms used


Image ID is a unique number for each image in this catalogue. It is handy to know this number if you want someone else to view the details for an image.

Geographic area is the name of the area or one of the feature in the area of the image. All names are approved names for the gazetteer

Capture date is the date the image was captured. Not to be confused with the date processed.

Satellite position uses a grid reference system to describe where a satellite was when an image was taken. It is only used for Landsat and SPOT imagery. For Landsat imagery the position is referred to by path and row. For SPOT imagery it is referred to by k and j.

Sensor is the name of the instrument capturing the image.

Spatial coverage is the geographical extents of the image.

Output format determines how your results will be delivered to you. Output options include files suitable for opening in other applications; HTML for any web browser, KML for GoogleEarth, Excel for Microsoft Excel and Word for Microsoft Word.

Stored format is how the image is being held in the Data Centre. This includes digital as well as hard copy.

Cloud Cover is the percentage of cloud that obscures your image.

Georeferenced The original image has been aligned to a known coordinate system so it can be viewed, queried, and analysed with other geographic data. The georeferencing may haveinvolved shifting, rotating, scaling, skewing, and in some cases warping, rubber sheeting, or orthorectifying the data.

Orthorectified The process of correcting the geometry of an image so that it appears as though each pixel were acquired from directly overhead. Orthorectification uses elevation data to correct terrain distortion in satellite imagery.

Subsetted Only part of the original image is saved. Working with only the region of interest (ROI) allows for faster processing rather than dealing with the full image.

Mosaic an assembly of multiple images matched in such a way as to show a continuous representation of an area.

Diapositive is a positive image stored on a glass plate or transparent plastic film.

Thematic data that has been derived from an image. e.g. vector layers.

Pan sharpened Pan-sharpening algorithms are used to sharpen multispectral data using high spatial resolution panchromatic data. An underlying assumption of these algorithms is that you can accurately estimate what the panchromatic data would look like using lower spatial resolution multispectral data.

Image Enhancement The original image has had operations applied to improve the appearance or usability by making specific features more detectable. Such operations can include contrast stretching, edge enhancement, filtering, smoothing, and sharpening.

Additional fields exist for the Russian Imagery

Film is an ID given to the film used for the image.

Run is the number of the run along which photos were taken. There are usually multiple runs for each film.

Height is the flying height above sea level.

Frame is the frame number of a photo. There are multiple frames associated with each run.

Focal length right is the focal length of the camera used for the oblique image to the right.