Guilford County SciVis V 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