Engineering topics

Davis, L. S.

Publications and source records attributed to Davis, L. S..

7 records

NASA NTRS1985

Texture classification by local rank correlation

A new approach to texture classification based on local rank correlation is proposed here. Its performance is compared with Laws' method which uses local convolution with feature masks. In the experiments, texture samples are classified based on their distribution of local statistics, either rank correlations or convolutions. The new method achieves generally optimal classification rates. It appears to be more robust because local order statistics are unaffected by local sample differences due to monotonic shifts of texture gray values and are less sensitive to noise.

Harwood, D.↗

NASA NTRS1984

Evidence accumulation for spatial reasoning

The evidence accumulation proces of an image understanding system is described enabling the system to perform top-down(goal-oriented) picture processing as well as bottom-up verification of consistent spatial relations among objects.

Matsuyama, T.↗

NASA NTRS1983

An experiment in multispectral, multitemporal crop classification using relaxation techniques

The paper describes the result of an experimental study concerning the use of probabilistic relaxation for improving pixel classification rates. Two LACIE sites were used in the study and in both cases, relaxation resulted in a marked improvement in classification rates.

Davis, L. S.↗

NASA NTRS1983

Image matching using Hough transforms

Image matching using Hough transforms is discussed. Known objects in imagery are used as input to the transforms which allow prediction of similar objects in the imagery.

Davis, L. S.↗

NASA NTRS1983

Image Matching Using Generalized Hough Transforms

An image matching system specifically designed to match dissimilar images is described. A set of blobs and ribbons is first extracted from each image, and then generalized Hough transform techniques are used to match these sets and compute the transformation that best registers the image. An example of the application of the approach to one pair of remotely sensed images is presented.

Davis, L. S.↗

NASA NTRS1982

Cooperative processes in image segmentation

Research into the role of cooperative, or relaxation, processes in image segmentation is surveyed. Cooperative processes can be employed at several levels of the segmentation process as a preprocessing enhancement step, during supervised or unsupervised pixel classification and, finally, for the interpretation of image segments based on segment properties and relations.

Davis, L. S.↗

NASA NTRS1974

Edge and line detection in ERTS imagery: A comparative study

Several local edge detection operators were applied to a set of ERTS pictures of the Monterey, Calif. area. Gradient operators performed consistently better than laplacian operators in detecting edges. It was also found that if a grayscale normalization operation, histogram flattening, was applied to the pictures first, the edge detector outputs were greatly enhanced. The use of interpolation for more accurate location of edges on a digital picture was also briefly investigated. Curve detection operators were applied to the edge detector outputs; this had the effect of enhancing the edges while suppressing noise.

Eberlein, R.↗