chapter 2 vector layers
本章教学要求：有关专业英语单词
introduction
erdas imagine ** designed to integrate two data types,raster and vector,into one system.the vector data structure in erdas imagine ** based on the arc** data model(developed by esri,inc.).th** chapter describes vector data,attribute **rmation,and symbolization.
you can use arc** coverages directly without importing them.
记住 figure 2-1:vector elements 中的英文词。arcg** integration
arcg** integration ** the method you use to access the data in a geodatabase.erdas imagine has always supported esri data formats such as coverages and shapefiles,and now,using arcg** vector integration,erdas imagine can also access cad and vpf data on the internet.
chapter 3
raster and vector data sources
本章教学要求：1、重点：satellite data部分
2其余部分，仅要求标题有关专业英语单词
introduction
th** chapter ** an introduction to the most common raster and vector data types that can be used with the erdas imagine software package.
the raster data types covered include:（see text，
importing and exporting（不用理会)
satellite data
there are several data acqu**ition options **ailable including photography,aerial sensors,and soph**ticated satellite scanners.however,a satellite system offers these advantages:
easily processed and analyzed by a computer.
many satellites orbit the earth,so the same area can be covered on a regular bas** for change detection.
once the satellite ** launched,the cost for data acqu**ition ** less than that for aircraft data.
satellites h**e very stable geometry,meaning that there ** less chance for d**tortion or skew in the final image.
satellite system
a satellite system ** composed of a scanner with sensors and a satellite platform.the sensors are made up of detectors.
（see the detailed in text）
satellite character**tics
the u.s.landsat and the french spot satellites are two important data acqu**ition satellites.they h**e several character**tics in common:
both scanners can produce nadir views.
they h**e sun-synchronous orbits,meaning that they rotate around the earth at the same rate as the earth rotates on its ax**,so data are always collected at the same local time of day over the same region.
they both record electromagnetic radiation in one or bands.multiband data are referred to as mult**pectral imagery.single band,or monochrome,imagery ** called panchromatic.
figure 3-1 mult**pectral imagery compar**on
ikonos（was launched in september of 1999）
the resolution of the panchromatic sensor ** 1 m.the resolution of the mult**pectral scanner ** 4 m.the swath width ** 13 km at nadir.
table 3-4:ikonos bands and w**elengths
补：美digitalglobel(earthwatch)公司的quickbird（快鸟）图像，波段分布与ikonos同，但pan和mult**pectral分辨率分别达0.6和2.4米，为民用卫星之最。irs(indian remote sensing satellite)
landsat 1-5(see the h**toty in text)
landsats 1,2,and 3 are no longer operating,but landsats 4 and 5 are still in orbit gathering data.
landsats 1,2,and 3 gathered mult**pectral scanner(mss)data and landsats 4 and 5 collect mss and tm data.
mss(mult**pectral scanner)
mss data are widely used for general geologic studies as well as vegetation inventories.
table 3-8:mss bands and w**elengths
tm（thematic mapper）
the tm scanner ** a mult**pectral scanning system much like the mss.tm has higher spatial,spectral,and radiometric resolution than mss.
the spatial resolution of tm ** 28.5×28.5 m for all bands except the thermal(band 6),which has a spatial resolution of 120×120 m.
table 3-9:tm bands and w**elengths
landsat 7
launched in 1999,uses enhanced thematic mapper plus(etm+)to observe the earth.
table 3-10:landsat 7 character**tics
nlaps
noaa polar orbiter data
**hrr
see table 3-11:**hrr bands and w**elengths,also figure 3-1.
orbview-3(us)类似 ikonos.
seawifs（sea-viewing wide field-of-view sensor）
spot
the sensors operate in two modes,mult**pectral（20m）and panchromatic(10m).
also see figure 3-1.
panchromatic
xs(see table 3-14:spot xs bands and w**elengths)
spot 4(was launched in 1998)
增加一个1.58 to 1.75 μm的近红外波段；see table 3-15.
补：spot 5—panchromatic 波段达2.5米分辨率。补：我国资源一号卫星cbers
radar data
researchers are finding that a combination of the character**tics of radar data and v**ible/infrared data ** providing a complete picture of the earth.in the last decade,the importance and applications of radar h**e grown rapidly.
advantages of using radar data
radar microw**es can penetrate the atmosphere day or night under virtually all weather conditions.全天候
under certain circumstances,radar can partially penetrate arid and hyperarid surfaces,revealing subsurface features of the earth.
for research on bodies of water.
radar sensors
radar images are generated by two different types of sensors:
slar(figure 3-4)
sar—uses a side-looking,fixed antenna to create a synthetic aperture.
active and passive sensors
an active radar sensor gives off a burst of coherent radiation that reflects from the target,unlike a passive microw**e sensor which simply receives the low-level radiation naturally emitted by targets.
applications for radar data
geology
classification
glaciology
oceanography
hydrology
ship monitoring
offshore oil activities
pollution monitoring
image data from aircraft
th** ** useful if there ** not time to wait for the next satellite to pass over a particular area,or if it ** necessary to achieve a specific spatial or spectral resolution that cannot be attained with satellite sensors.
gps data
chapter 4 image d**play
本章教学要求：1、重点：rgb&d**playing raster layers 部分
2、using the viewer 部分，结合实习1
introduction
th** section defines some important terms that are relevant to image d**play.th** may differ from other systems,such as microsoft windows nt.
the d**play hardware contains the memory that ** used to produce the image.th** hardware determines which types of d**plays are **ailable(e.g.,true color or pseudo color)and the pixel depth(e.g.,8-bit or 24-bit).
d**play memory size
d**play resolution—the number of pixels that can be viewed on the d**play screen.
the number of bits for each pixel or pixel depth.
pixel（file pixel&d**play pixel）
the data file value(s)for one data unit in an image
one grid location on a d**play or printout
to d**play an image,a file pixel that cons**ts of one or numbers must be transformed into a d**play pixel with properties that can be seen,such as brightness and color.
colors（rgb）
red,green,and blue can be added together to produce a wide variety of colors,are therefore the additive primary colors.
（三原色和三补色，及其它颜色特性，推荐阅读彭书 58-66页）
color guns
on a d**play,color guns direct electron beams that fall on red,green,and blue phosphors.the phosphors glow at certain frequencies to produce different colors.
the combination of the three color guns,each with 28 possible brightness values,yields 224 or 16,777,216 possible colors for each pixel on a 24-bit d**play.(line 7-9,page 110)
colormap and colorcells
a colormap ** an ordered set of colorcells,which ** used to perform a function on a set of input values.to d**play or print an image,the colormap translates data file values in memory into brightness values for each color gun.
（see table 4-1）
colorcells
there ** a colorcell in the colormap for each data file value.he red,green,and blue values assigned to the colorcell control the brightness of the color guns for the d**played pixel.
colormap vs.lookup table
the colormap ** a function of the d**play hardware,whereas a lookup table ** a function of erdas imagine.
d**play types
8-bit pseudocolor
24-bit directcolor
24-bit truecolor
32-bit d**plays
a 32-bit d**play ** a combination of an 8-bit pseudocolor and 24-bit directcolor,or truecolor d**play.
8-bit pseudocolor：a colormap with 256 colorcells.
th** d**play grants a small number of colors to erdas imagine.it works well with thematic raster layers containing less than 200 colors and with gray scale continuous raster layers.for image files with three continuous raster layers(bands),the colors are severely limited.
24-bit directcolor or 24-bit truecolor
两种方式（colorcell or color gun）达到24位彩色实时显示的目的：
enables you to view up to three continuous raster layers(bands)of data at one time,creating d**played pixels that represent the relationships between the bands by their colors.
pc d**plays
erdas imagine for microsoft windows nt supports the following v**ual type and pixeldepths:
8-bit pseudocolor
24-bit truecolor
8-bit pseudocolor
an 8-bit pseudocolor d**play for the pc uses the same type of colormap as the x windows 8-bit pseudocolor d**play.
24-bit truecolor
a 24-bit truecolor d**play for the pc assigns colors the same way as the x windows 24-bit truecolor d**play.
d**playing raster layers
continuous raster layers
an image file(.img)can contain>3 continuous raster layers;therefore,when d**playing an image file with continuous raster layers,it ** possible to assign which layers(bands)are to be d**played with each of the three color guns.
band assignments are often expressed in r,g,b order.e.g.
landsat tm—natural color:3,2,1
landsat tm—color-infrared:4,3,2
spot mult**pectral—color-infrared:3,2,1