USGS MIPS Grad Documentation

USGS MIPS Grad Documentation

This program applies a convolution filter to an

Files

This program requires as input an unsigned 16-bit image file and will produce the same type image file. The following information is transferred from the input file to the output file(if appropriate):

Image labels
Mosaic labels
Projection labels
Sonar labels
Navigation file
History file

Parameters

ROBERTS, SOBEL or MODIFIED: These options are used to select the type of gradient filter, either the Roberts 2x2, Sobel 3x3, or Modified 4x4. The default is the Modified 4x4 gradient filter.

Uses

This program is useful for enhancing or detecting edges in an image. Unlike the program DERIVE, it detects edges in all directions with equal sensitvity. The resultant image can be thresholded using the program Stretch to produce an edge image. For example,

0;0 X-1;0 X;255 255;255

Where,

X = threshold DN

Note that too high a threshold does not permit detection of subtle edges and too low a threshold can cause noise to be detected. The only difference between the gradient filters is the size of the window. As the window size increases the thickness of the edges increases and there are fewer discontinuities in the edges.

Examples

From left to right, original Landsat MSS Band 6, Roberts gradient filter, and Modified gradient filter.

[Example Image]