新：求The ERDAS Field Guide第一章内容上次那个不太对,

新：求The ERDAS Field Guide第一章内容上次那个不太对,
新：求The ERDAS Field Guide第一章内容
上次那个不太对,

新：求The ERDAS Field Guide第一章内容上次那个不太对,
Chapter 1 Raster Data
本章主要教学目标：熟悉遥感基础概念和专业词语
Introduction
The ERDAS IMAGINE system incorporates the functions of both image processing and GIS.
Image Data
Image data are digital representations of the Earth. Image data are stored in data files, also called image files. The data consist only of numbers. These representations form images when they are displayed on a screen or are output to hardcopy.
Each number in an image file is a data file value. Data file values are sometimes referred to as pixels. The term pixel is abbreviated from picture element. A pixel is the smallest part of a picture (the area being scanned) with a single value. The data file value is the measured brightness value of the pixel at a specific wavelength.
Raster image data are laid out in a grid similar to the squares on a checkerboard. Each cell of the grid is represented by a pixel, also known as a grid cell.
In remotely sensed image data, each pixel represents an area of the Earth at a specific location. The data file value assigned to that pixel is the record of reflected radiation or emitted heat from the Earth’s surface at that location.
Bands
Image data may include several bands of information. Each band is a set of data file values for a specific portion of the electromagnetic spectrum of reflected light or emitted heat or some other user-defined information created by combining or enhancing the original bands, or creating new bands from other sources.
Coordinate Systems
File coordinates refer to the location of the pixels within the image (data) file. File coordinates for the pixel in the upper left corner of the image always begin at 0, 0.
Map coordinates may be expressed in one of a number of map coordinate or projection systems.
Remote Sensing
Remote sensing is the acquisition of data about an object or scene by a sensor that is far from the object (Colwell, 1983). Usually, remotely sensed data refer to data of the Earth collected from sensors on satellites or aircraft.
Electromagnetic Radiation Spectrum
（Figure 1-3）
EMR,SWIR and LWIR
Absorption /Reflection Spectra
It is necessary to understand how vegetation, soils, water, and other land covers reflect and absorb radiation. The study of the absorption and reflection of EMR waves is called spectroscopy. To fully utilize a visible/infrared (VIS/IR) multispectral data set and properly apply enhancement algorithms, it is necessary to understand the basic principles.
Solar radiation must travel through the Earth’s atmosphere before it reaches the Earth’s surface.
Figure 1-4 (Solar irradiation AND Atmospheric Absorption)
When an electromagnetic wave (solar illumination in this case) strikes a target surface, three interactions are possible (Elachi, 1987):
• reflection
• transmission
• scattering
重要的是：Reflectance Spectra. Anyway:
It is the reflected radiation that is measured by the remote sensor. Remotely sensed data are made up of reflectance values. The resulting reflectance values translate into discrete digital numbers (or values) recorded by the sensing device. These gray scale values fit within a certain bit range (such as 0 to 255, which is 8-bit data) depending on the characteristics of the sensor. Each satellite sensor detector is designed to record a specific portion of the electromagnetic spectrum. For example, Landsat Thematic Mapper (TM) band 1 records the 0.45 to 0.52 mm portion of the spectrum and is designed for water body penetration, making it useful for coastal water mapping.
The use of VIS/IR imagery for target discrimination is based on the reflectance spectrum of the material of interest (see Figure 1-6,加上可见光波段微弱的水体反射曲线). Every material has a characteristic spectrum based on the chemical composition of the material. When sunlight strikes a target, certain wavelengths are absorbed by the chemical bonds; the rest are reflected back to the sensor. It is, in fact, the wavelengths that are not returned to the sensor that provide information about the imaged area.
Specific wavelengths are also absorbed by gases in the atmosphere (H2O vapor, CO2, O2, etc.). If the atmosphere absorbs a large percentage of the radiation, it becomes difficult or impossible to use that particular wavelength(s) to study the Earth. Figure 1-6 shows how Landsat TM bands 5 and 7 were carefully placed to avoid these regions.
Hyperspectral Data
As remote sensing moves toward the use of more and narrower bands (for example, AVIRIS with 224 bands only 10 nm wide), absorption by specific atmospheric gases must be considered. These multiband sensors are called hyperspectral sensors.
Figure 1-7 shows detail of the absorption spectra of three clay minerals. Because of the wide bandpass (2080 to 2350 nm) of TM band 7, it is not possible to discern between these three minerals with the Landsat sensor. As mentioned, the AVIRIS hyperspectral sensor has a large number of approximately 10 nm wide bands. With the proper selection of band ratios, mineral identification becomes possible.
Imaging Radar Data
Radar remote sensors can be broken into two broad categories: passive and active. The passive sensors record the very low intensity, microwave radiation naturally emitted by the Earth. Because of the very low intensity, these images have low spatial resolution (i.e., large pixel size).
It is the active sensors, termed imaging radar, that are introducing a new generation of satellite imagery to remote sensing. To produce an image, these satellites emit a directed beam of microwave energy at the target, and then collect the backscattered (reflected) radiation from the target scene.
Resolution
Spectral Resolution
refers to the specific wavelength intervals in electro- magnetic spectrum that a sensor can record.
Spatial Resolution：
a measure of the smallest object that can be resolved by the sensor, or the area on the ground represented by each pixel.
Scale & Spatial Resolution
Instantaneous Field of View
Radiometric Resolution：
is referred to by the number of bits into which the recorded energy is divided.
Temporal Resolution：
refers to how often a sensor obtains imagery of a particular area.
Data Correction
注意： it ≠ Rectification of Chapter 10
There are several types of errors that can be manifested in remotely sensed data. Among these are line dropout and striping. These errors can be corrected to an extent in GIS by radiometric and geometric correction functions.
Data Storage
Storage Formats
BIL (band interleaved by line)
BSQ (band sequential) format
（参照GIS§2.3.3.4多层栅格数据结构的文件格式）
Storage Media
Calculating Disk Space
（参照GIS第二章§2.3.3.1）
ERDAS IMAGINE Format (.img) Figure 1-13
Thematic & Continuous Raster Layers
（参照GIS§2.3.3.2:表达点线面地物的栅格数据和实录型栅格数据）
Image File Organization
Consistent Naming Convention
Keeping Track of Image Files