Friday 2 May 2014

Background Images

Often researches have a map or satellite image, a jpeg or bitmap, of the area that the tracked animal has travelled over. In this case, it is extremely useful to be able use this image as background for visual analysis and for figures in reports.

Ranges 8 allows background images but the alignment implementation is very basic. It insists only on two coordinates, the top right and bottom left corners of the image, which is not enough to allow for all the possible distortions:  rotation, shear, scale, and translation. This can be handled by applying an affine transform to the image and for this we need four coordinates.

Ranges 9 gathers these coordinates with a clever new interface. The user loads the image and it is displayed with four markers defining the points on the image. He moves the markers by dragging them into a position on the image that he know the real world coordinate of, then enters these coordinates into the panel against the marker.

The image alignment dialog

Users can drag to scroll and select areas to zoom as well as panning and zooming with the familiar controls, just as they can with the new graphics screen.

Zoomed in to the second alignment marker
Aligned images are saved along with the alignment points in a new file type .ima.These can then be loaded as the background to a location or edge file.

The image as background for an edge file

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