Guilford County SciVisV202.02

Applying Pixel Values to Digital

Images

Digital Images Gather Data by Remote Sensing Remote Sensing is the

process of gathering information without touching it.

Satellites use a number of different sensors (IR, UV, Visible light, Radio) to record information

Digital Images Gather Data by Remote Sensing Example of remote sensing

include: Microscopes and

Telescopes Echolocation Infrared Radiation (Heat..

Heat sensors) Sounds waves used in

medical Imaging (MRI) X-rays used to detect to

detect broken bone

What are Digital Images? Digital images are

composed of pixels arranged in rows and columns.

Each pixel carries a numerical values or digital number (DN).

Colors or shade of gray (brightness) are assigned to each DN.

What are Digital Images? A LUT (Look-Up table) is

used to show the scale relationship between each pixel’s DN and its assigned color or gray brightness value.

Changing the LUT scale controls the appearance of the image.

What are Digital Images? Digital data can be manipulated Pseudocolors (false colors) can be assigned to

an image using the LUT. Uses would include:

Enhance weather images to see moisture, wind patterns, solar energy, etc.

Color coding Medical Images Enhancing satellite images to see fire, glacier

movement, forest depletion, etc.

Multi-spectral Remote Sensing Recording energy in the red, green, blue, IR, UV,

or other parts of the electromagnetic spectrum.

Multi-spectral Remote Sensing Multi-spectral remote

sensing measures the amount of energy reflected in bands that correspond to specific colors.

Scientists can obtain information from these wavelengths (color).

For example, scientists can pick out the range of color of marijuana plants grown.

Contrast and Brightness Levels The BRIGHTNESS is the intensity of white in

an image. The CONTRAST or Value is the difference

between the lightness and darkness of an image.

Measuring in Area Renderings The portion of the earth

is dependent on the height of the satellite. Most weather satellites use the scale of 16 square miles equals 1 pixel. Programs like Scion Image allow you to set these scales.

The curve of the earth may add variation to these renderings.

Histograms in Area Renderings Histograms are displayed as a

bar graph. The height of the bar displays the number of pixels.

Density Slicing Density slicing allows you to

highlight a range of pixel values in the LUT.

The highlighted pixels help visualize areas of interest.

Digital Elevation Models (DEM’s) DEM’s are images

where DN (digital number) or grayscale values represent elevation.

A digital image can be converted into a relief map.

Elevation Calibration (Calibrated DEM’s) Take the data from a

DEM to apply known elevation to calculate other elevations.

Mapping out the sea surface floor is an example of using this method.

The End