viernes, 28 de noviembre de 2008

Colors Definitions and Models


Colors Definitions and Models



William Benigno Barragan Zaque
University of applied sciences stuttgart
Department of surveying and geoinformatic



Nabila Ibrahim Abd El – Hamed

National Authority for Remote Sensing and Space Sciences (NARRS),
CAIRO


December 2004


1 Abstract
Colors have importance in live. The history of the concept of the colors started in 1666, when Isaac Newton presented his color circle. He demonstrated that light contains all wavelengths of the visible spectrum. The human eyes can perceive wavelengths, between 350 and 780 nanometers. We can define the color as a sensation, which occurs when light energy, incident on the retina and is interpreted by the brain. The principal models that define the colors are: RGB, it is the most common model which is used in television and computers. It creates the colors by combining different percentages of three primary colors (red, green and blue). The other model for the presentation of colors is called CMYK; printing is based on this, which works with the colors Cyan, Magenta, Yellow and Black. On the other hand HSB model defines the colors by Hue, Saturation and Brightness in percentages.
Using of the colors has a loot advantages in different fields. In education it is important as a tool for memorizing and easy reading. The same form is used for abstraction of the important information and presentation of results.


Keywords:
Color, Newton color circle, wavelength, visual spectrum range, RGB Model, CMY(K) Model, HSB Model, Primary colors.


Table of contents

1 Abstract 2
2 Table of Figures 4
3 Introduction 5
4 Color definition 5
5 The human color perception 5
5.1 Observation of the colors 6
6 Models that defined colors 7
6.1 RGB Model 8
6.2 CMYK Model 8
6.3 HSB Model 10
7 Applications of the colors 11
7.1 Satellite Images 11
7.2 Education 11
7.3 Information 11
7.4 Presentation 11
7.5 To improve abilities: 12
8 Conclusions 13
9 References 14
10 Glossary of terms 15
11 Index 16


2 Table of Figures


Figure 1: Process in the human color perception 7
Figure 2: RGB Model 8
Figure 3: CMYK Model 9
Figure 4: HSB Model 10


3 Introduction
In many areas of the knowledge and in the sciences, the colors are very important. Sensations, animate status, symbols, emotions … and many situations that are too difficult to understand when doesn’t any have help of the colors. For example can be used, in communication, smile, gesture and laugh, but if these expressions are integrate with appropriate color, it is possible that the interpretation of this expression can be are more real.
It is true that the use of colors is continue. The colors are used in every minute of the normal live of people.
In the following pages are given description about the physical formation of the colors in the human vision and the principal models used for the formation the Them.

4 Color definition

When we speak about colors it is necessary to speak about Isaac Newton who made a study of color starting at the age of 23 in 1666 and developed the useful Newton color circle which gives the insight about complementary colors and additive color Theory. We can consider that his contribution was the idea that white light contains all wavelengths of the visible spectrum. He demonstrated this fact with experiments on the dispersion of light in glass prisms. This is the basis to Know that the light is a form of electromagnetic radiation.

Electromagnetic energy travels as waves characterized by their frequency and their wavelength. The electromagnetic spectrum includes energy that the human eye can not perceive for example: radio waves, or infrared, but there is a part of the electromagnetic spectrum that our eyes can perceive, visible spectrum, between 350 and 780 nanometers (nm) is called light. Distinct frequencies are visible as distinct colors.
We can define color as a sensation, which occurs when the brain interprets light energy, incident on the retina.

5 The human color perception

Our eyes have three sets of sensors, called cones with peak sensitivities at light frequencies that we called red (580 nm), green (540 nm) and blue (450 nm). Light at any wavelength in the visual spectrum range, will excite one or more of these three types of sensors. Our perception of which color we are seeing is determined by which combinations of sensors are excited and by how much. Wherever color can be represented as a combination of the three primary colors.
5.1 Observation of the colors
Figure 1 show 8 steps for the observation of the colors.
1. The most important thing for the formation of the colors in the brain is the light that can be produced of natural form by the sun or the artificial form by the normal lamps.
2. The second step is the transitions of the energy in three different wavelengths, which represent the colors: red, green, and blue.
3. The object that we see absorbs some wavelength, according to the composition of this object.
4. The wavelength that the object doesn’t absorb is reflected.
5. The human eye receives the information of wavelength that is reflected by the object.
6. The retina of the human eye transmits the information to cones.
7. The cones can identify the color of the object.
8. It is possible to see the object according to its color.



















Figure 1: Process in the human color perception

6 Models that defined colors


The are thee different models to define colors:
RGB Model: This model uses the colors red green, and blue, and the colors are defined by percentage of those colors.

CMY(K) Model: This model uses the colors cyan, magenta, yellow, and black, and the colors are defined by percentage of those colors.

HSB Model: The color are defined by their Hue Saturation Brightness: with the HSB model, all colors can be defined by expressing their levels of hue, saturation, and brightness, in percentages.



6.1 RGB Model
This model is the most important for the computers and television because they create the colors based on RGB model. Monitor and television can create millions of colors by combining different percentages of three primaries, red, green and blue. While using the image processing software like “Photoshop” you can see that these RGB colors are added with the help of numerical value, that is possible to identify from 0 to 255 different values. Figure 2. With RGB, mixing of red and green equally gives yellow, mixing of green and blue creates cyan and the mixing of red and blue creates magenta. When all the three colors, red, green and blue are mixed equally they produce white light. Hence it is called Additive color model. Another RGB model based example is the human eye itself and scanners.
The basic advantage of RGB model is that it is useful for full color editing because it has wide range of colors. But at the same time this model is said to be device dependent. It means that the way the colors are displayed on the screen depends on the hardware used to display it.











Figure 2: RGB Model
6.2 CMYK Model
Printing inks are based on this model, CMY is opposite model of RGB. With the full presence of cyan, magenta and yellow we get black. But practically in the printing industry it is impossible to create black with these three colors. The result of the mixture of CMY is muddy brown due to the impurities of the printing inks. Hence black ink is added to get solid black. The outcome of this process CMYK model and k stand for black color, which is also recognized as 'key' color. Since black is a full presence of color, you will have to subtract the levels of cyan, magenta and yellow to produce the lighter colors. This can be explained in different way. When light falls on the green surface or green ink, it absorbs (subtracts) all the colors from light except green. Hence the model is called subtractive model. Print production is based on this model. Figure 3











Figure 3: CMYK Model


6.3 HSB Model
Color can be described conceptually by a three-dimensional HSB model:
Hue (H) refers to the basic color in terms of one or two dominant primary colors (red, or blue-green, for example); it is measured as a position on the standard color wheel, and is described as an angle in degrees, between 0 to 360.
Saturation, sometimes called chroma, is the strength or purity of the color. Saturation represents the amount of gray in proportion to the hue, measured as a percentage from 0% (gray) to 100% (fully saturated). On the standard color wheel, saturation increases from the center to the edge.
Brightness (B) refers to the color’s proximity to white or black, which is a function of the amplitude of the light that stimulates the eye's receptors; it is also measured as a percentage - if any hue has a brightness of 0%, it becomes black, with 100% it becomes fully light. Figure 4. You can use the HSB model in Photoshop to define a color in the Color palette or Color Picker dialog box, but there is no HSB mode available for creating and editing images.












Figure 4: HSB Model




7 Applications of the colors
7.1 Satellite Images

Colors can be used in Satellite Images. It is possible to make different combination between colors and bands of the images, in order to identify, resources, different concentrations of materials, different heights etc. Some commons applications are:

• In Geological applications for Mineral Exploration and Monitoring Miens.
• In Digital Elevation Models, for observations of Slop Aspect.
• In agriculture applications for identify different types of vegetation.
• Marin Applications for Detecting the Bottom of the See & its inhabitance.
• Climate Applications for Real Time Data for Monitoring Hurricanes.

7.2 Education
For more complex tasks like reading, memorizing, drawing conclusions, or deciding the effect of color cannot as easily proven. The color can be used in pedagogical process specially in the primary school, for to teach to the children.

7.3 Information
The use of colors can effectively support human performance in visual image interpretation processing. When colors are used correctly the interpretation of information is easier.


7.4 Presentation
Even if this is not the case, users find colors more pleasant, more aesthetically pleasing, inspiring or useful than a monochromatic presentation. Colors can increase the users' self-assurance to find their way around and to find the information they are searching for.
.
7.5 To improve abilities:
• Separating figure from ground, that is, separating the important from the less important.
• Discerning the inner structure of objects, finding groupings.
• Searching, discovering, and localizing objects.
• Recognizing and remembering.

.



8 Conclusions


Colors have a fundamental physical base in the electromagnetic spectrum. It permits to classify the kind of electromagnetic energy the human eye can identify. The human eyes can identify the colors by sensors called cones. These sensors are sensitive at light frequencies for the three primary colors red, green and blue.

The observation of the colors is a process where there are interactions between factors as: light, wavelengths, object, the retina of the eye and the brain.

There are three models to define colors, each of them use different techniques and methods. The most common model is used in television and computers, and is called RGB, this works with a combination of three primary color (red, green and blue).

There are two models, the first one is CMY(K) that use the colors (Cyan, Magenta, Yellow and Black) and the second one is HSB (Hue, Saturation and Brightness) it woks with saturation and brightness. These models are very important in cartographic, topographic and engineering applications, also is used for software like arc-view and geomedia.

The most important think is that every model define each white color precision, because presents one numerical value for each color to make then unique and unrepeatable.

Color is important in several fields of knowledge and science existing a good integration between high technology and human resource to apply then in real problems and looking for new alternatives for explorations to improve life conditions.

Colors are very important in some areas as education, information and communication, because make easier understand the information around us, also can represent sensations and express sentiments.









9 References

• Theory perceive the color, introduction to graphic of computer
• http://semmix.pl/color
• Remote Sensing Tutorial http://rst.gsfc.nasa.gov
• USGS: Earthshots http://www.usgs.gov/Earthshots
• World of Beams http://cbp-1.lbl.gov
• R.M. Boynton, Human Color Vision, Special Limited Edition, Optical Society of America, Washington D.C., 1992.
• R.W.G. Hunt, Measuring color 3rd Ed., Fountain Press, England, 1998.
• M.D. Fairchild, Color Appearance Models, Addison-Wesley, Reading,



10 Glossary of terms

Brightness -- the perceived intensity of the light. Intensity is the radiant energy emitted per
Chromacity -- the purity and dominant frequency of a light grouped
unit time, per unit solid angle, and per unit projected area of the source.(ex.: light vs. dark red)
Complementary colors -- two colors that when combined produce white light. (ex.: red - cyan, green - magenta, blue - yellow).
Hue -- The "color" of a color specified by the dominant wavelength also called the dominant frequency, (ex.: "red" vs "green"). This is the most obvious dimension of a color and identifies a color by name, i.e., red, yellow, blue. Every color falls into a definite hue category.
Luminance or Value -- the total power of the light determines the "lightness" of a color (ex.: light vs. dark red). Brightness (radiant energy) is related to the luminance of the source
Primary colors -- the two or three colors used to produce other colors in a color model.
Saturation or Purity -- the "colorfulness" of the color (ex.: vivid red vs. dull red). Purity describes how washed-out or "pure" (vivid) the color of the light appears. Pastels and pale colors are described as less pure.




11 Index


Brightness 7
CMYK Model 8
colors 5
HSB Model 10
Hue 7
Information 11
models 7
perception 5
Presentation 11
RGB Model 8
Saturation 7
spectrum 5
To improve abilities 12
To learn 11
wavelength 6

GPS MODERNIZATION

Dip-Ing -William Barragán Zaque
Msc. Photogrammetry and Geoinformatics

University of applied sciences Stuttgart
Department of surveying and geoinformática
wbarragan@gmail.com

Abd-el-Hamed Nabial Ibrahim

Msc. Photogrammetry and Geoinformatics

University of applied sciences Stuttgart
Department of surveying and geoinformática
Nabila_gis@yahoo.com

THE GPS MODERNIZATION PROGRAM: IMPACT IN CIVIL USERS

1. GPS Modernization

United States government wants GPS to be the best Global Navigation Satellite System (GNSS) in the world. The system is more than 25 years old and upgrades are needed. As old satellites are taken out of operation, there is an opportunity to replace them with upgraded satellites.

GPS is being modernized in order to further improve positioning, navigation and timing capabilities for both civil and military users. The modernization initiative will result in substantial improvements in GPS positioning accuracy. Removal of Selective Availability (SA) in May 2000 was the first step in the GPS Modernization initiative.

This immediately increased the accuracy of stand‑alone GPS receivers from 30‑100 meters to about 10 meters. SA removal has also benefited fleet management – making tracking the locations of taxis, buses, tractor trailers and boxcars more efficient, especially in crowded parking lots and railway yards. Removal of SA has increased the safety of GPS for non-precision runway approaches and generally improved pilot situational awareness. Recreational benefits include the ability to more precisely locate favorite fishing holes, boating obstacles, and game left for future retrieval. According to the U.S. government’s 2001 Federal Radionavigation Systems report, “SPS (now) provides a global average predictable positioning accuracy of 13 meters (95 percent) horizontally and 22 meters (95 percent) vertically.”


2. New Signals

In the future, when combined with the current civil signal at 1575.42 MHz, the new signals will significantly improve the robustness and reliability of GPS for civil users. Estimated accuracy is one meter or better in real‑time. This new capability will spur new applications for GPS, further expanding the rapidly growing market for GPS equipment and services worldwide.

The second civil signal (called L2C) will be located at 1227.60 MHz along with the current military signal, and will be available for general use in non‑safety‑critical applications. L2C will include a more sophisticated code and is expected to become the most popular GPS signal used in the future. The new signals will not reach initial operational capability (IOC) until 18 satellites are in orbit (probably 2008).

A third civil signal will meet the needs of critical safety‑of‑life applications such as civil aviation. The third civil signal will be located at 1176.45 MHz, within a portion of the spectrum that is allocated internationally for aeronautical radio navigation services. It will provide a higher power level than other carriers and will use a larger bandwidth, enabling longer codes. As a result, acquiring and tracking weak signals will be much easier. It will be implemented beginning with a satellite scheduled for launch in 2005. IOC should occur for the new civil signal at L5 by 2012.

3. GPS Block III

GPS Block III will be a totally new system, not another variation of GPS II. The idea is to put some of the functionality now provided from the ground into the space segment – advantages are enhanced security, ability to incorporate data from other monitoring stations, and performance improvements brought about by making the constellation self-synchronizing. The overall goal is to provide flexibility and robustness to meet evolving military and civil requirements for the next 30 years.

4. Other Improvements

Several improvements to the operational control segment will improve the capability to monitor all signals broadcast from the constellation, make the control network more robust, improve the positioning accuracy of both the civil and military services, and add new functions that are necessary to control the modernized satellites.

A new military signal (M code) will be added on the L1 and L2 frequencies for the Department of Defense (DoD). In addition, a military spot beam will be added to new satellites. The military spot beam is intended to overcome jamming by increasing the power over a limited area. Satellites with all the enhancements will cost over $80 million each.

The current GPS modernization effort should carry the constellation through approximately the year 2010. A new generation of satellites and ground control facilities will be developed for use beyond 2010 through approximately 2030.

5. Other Global Navigation Satellite Systems (GNSS)

GLONASS is a Russian satellite navigation system which now consists of 10 healthy satellites. Some GPS receiver manufacturers have incorporated the capability to receive both GPS and GLONASS signals; this increases the availability of satellites and the integrity of the combined system.

Galileo is Europe's contribution to the next generation Global Navigation Satellite System (GNSS). Unlike GPS, which is funded by the public sector and operated by the U.S. Air Force, Galileo will be a civil‑controlled system that draws on both public and private sectors for funding. The service will be free at the point of use, but a range of chargeable services with additional features will also be offered. These additional features would include improved reception, accuracy and availability.

6. The Future of GPS

Look for autonomous GPS accuracy at the centimeter level within 10 years. GPS equipment capabilities are continually improving, and GPS receivers are being integrated into many other kinds of equipment (ex: cell phones, PDAs)

Receiver sizes and prices continue to decrease Budget problems seem to be an ever-present reality. For now, the U.S. and other countries are cooperating on development and operation of global navigation satellite systems (GNSSs) this cooperation has many benefits for users, including increased accuracy when using receivers that can process signals from more than one system.