形容秋天的句子-濮阳市人事考试网

GeoTiff格式读取注意事项：
1．GeoKey directory前4个数值为头信息；
2．GeoTiff修正号表示为.；
3．Header={KeyDirectoryVersion, KeyRevision, MinorRevision,
NumberOfKeys}目前DirectoryVersion 号为1,NumberOfKeys表明Key的
个数
4．KeyEntry = { KeyID, TIFFTagLocation, Count, Value_Offset }
其中，TIFFTagLocation表示哪个tag存放值，如果值为0则表示值为
SHORT类型 且包含在Value_Offset元素中；
此外还有GeoTagDoubleParams双精度 型,该域ID号为34736，保存不定
个数的double型GeoKeys，FLOAT要转化成d ouble型才能存在该种Tag
中；
GeoTagASCIIParamsASCII型， 该域ID号为34737，保存不定长度的
ASCII型GeoKeys,每个GeoKey结束的位置 加一个分割字符“|” ，一般只
有Citation的Key才为ASCII型；
5．GeoTiff支持的3种坐标空间（如文章）；
6．GeoTiff中6个GeoTa g域的具体含义（如文章），注意其中对于
KeyEntry内容的详细描述；
7．图像数据地理编码的具体步骤（如文章）；
8．栅格空间向模型空间的转换步骤（如文章）；
9．举例，如下：
GeoKeyDirectoryTag=( 1, 1, 2, 6,
1024, 0, 1, 2,
1026, 34737,12, 0,
2048, 0, 1, 32767,
2049, 34737,14, 12,
2050, 0, 1, 6,
2051, 34736, 1, 0 )

GeoDoubleParamsTag(34736)=(1.5)
Geo AsciiParamsTag(34737)=(
第一行表明这是一个版本号为1的GeoTIFF GeoKey目录，键的版本为Rev.
1.2，在这个标签中定义了6个键。
下一行定义第一个键(ID=1024 = GTModelTypeGeoKey)，值为2(Geo graphic)，
直接放在元素列表中（因为TIFFTagLocation=0）；
下一行键1026(the GTCitationGeoKey)，列在GeoAsciiParam sTag(34737)数组
中开始于偏移0，数到第12个字节，所以其值为（”|”被转换
为结束符了）
再下面一行，键2051(GeogLinearUnitSizeGeoKey) 位于GeoDoubleParamsTag
(34736), 偏移为0所以值为1.5
key2049的值为(GeogCitationGeoKey) is 。
10．怀疑在TIFF中用SamplesPerPixel, PlanarConfiguration, ExtraSamples来表示
多光谱数据,应该从这些地方入手,察看!
11．
以下为地理坐标与投影坐标转换的示意：
Projected_CS = Geographic_CS + Projection
Geographic_CS = Angular_Unit + Geodetic_Datum + Prime_Meridian
Projection = Linear Unit + Coord_Transf_Method + CT_Parameters
Coord_Transf_Method = { TransverseMercator | LambertCC | ...}
CT_Parameters = {OriginLatitude + StandardParallel+...}
12．纬度赤 道以北为正，赤道以南为负；经度本初子午线以东为正，以西为
负；GeoTiff中也包括了不以格林 尼治天文台为零点的经度
13．在用地理坐标系描述一个点时，地球和椭球的关系一定要定义
14．A geographic coordinate system has two axes, latitude and longitude, which are
only unambiguous when both of the related prime meridian and geodetic datum are
given, and in turn the geodetic datum definition includes the definition of an
ellipsoid地理坐标系定义需要的条件：经纬度，本初子午线，大地基准点
15．
ModelPixelScaleTag
ModelTiepointTag
R ------------ OR --------------> M

(I,J,K) ModelTransformationTag (X,Y,Z)
表示将栅格图像空间和模型空间绑在一起，表示模型空间如何将坐标与地球相
应
16 ．ModelPixelScaleTag（在图像发生旋转和剪切时不能使用该Tag）和
TiePo int：通过这两个来表示图像空间和模型空间之间的关系
17．ModelTransformationTag = (a,b,c,d,e....m,n,o,p)：如果ModelTiepointTag和
Mod elPixelScaleTag已经定义，则不定义该标签，在定义一个Tiepoint和
Mode lPixelScale可以计算该转换矩阵
18．下面给出了如何定义一个栅格图像空间坐标所需要的Tag
Here is a 4-step guide to producing a set of Baseline GeoTIFF tags for defining
coordinate transformation information of a raster dataset.
Step 1: Establish the Raster Space coordinate system used:
RasterPixelIsArea or RasterPixelIsPoint.
Step 2: Establishdefine the model space Type in which the image is to be georeferenced.
Usually this will be a Projected Coordinate system (PCS). If you are geocoding this data
set, then the model space is defined to be the corresponding geographic, geocentric or
Projected coordinate system (skip to the
this).
Step 3: Identify the nature of the transformations needed to tie the raster data down to
the model space coordinate system:
注意以下情况分类考虑，读写都要考虑
Case 1: The model-location of a raster point (x,y) is known, but not the scale or
orientations:Use the ModelTiepointTag to define the (X,Y,Z) coordinates of the known
raster point.
Case 2: The location of three non-collinear raster points are known exactly, but
the linearity of the transformation is not known. Use the ModelTiepointTag to define the
(X,Y,Z) coordinates of all three known raster points. Do not compute or define the
ModelPixelScale or ModelTransformation tag.
Case 3: The position and scale of the data is known exactly, and no rotation or
shearing is needed to fit into the model space. Use the ModelTiepointTag to define the
(X,Y,Z) coordinates of the known raster point, and the ModelPixelScaleTag to specify the
scale.

Case 4: The raster data requires rotation andor lateral shearing to fit into the defined
model space: Use the ModelTransformation matrix to define the transformation.
Case 5: The raster data cannot be fit into the model space with a simple affine
transformation (rubber- sheeting required). Use only the ModelTiepoint tag, and specify as
many tiepoints as your application requires. Note, however, that this is not a Baseline
GeoTIFF implementation, and should not be used for interchange; it is recommended that
the image be geometrically rectified first, and put into a standard projected coordinate
system.
Step 4: Install the defined tag values in the TIFF file and close it.
19．Cookbook for Geocoding Data
Geocoding的整个流程
Step 1: Determine the Coordinate system type of the raster data, based on the nature of
the data: pixels derived from scanners or other optical devices represent areas, and most
commonly will use the RasterPixelIsArea coordinate system. Pixel data such as digital
elevation models represent points, and will probably use RasterPixelIsPoint coordinates.
Store in: GTRasterTypeGeoKey保存栅格图像的信息
Step 2: Determine which class of model space coordinates are most natural for this
dataset:Geographic, Geocentric, or Projected Coordinate System. Usually this will be
PCS.
Store in: GTModelTypeGeoKey保存模型空间坐标系类型的信息
Step 3: This step depends on the GTModelType:
case PCS: the PCS projection system. Most of the
PCS's used in standard State Plane and national grid systems
are defined, so check this list first; the EPSG index in
section 6.4 may be useful for this purpose.
察看6.4部分，可以得到非常有用的信息，关于标准的坐标系，保存在以下
Key中
Store in: ProjectedCSTypeGeoKey, ProjectedCSTypeGeoKey
If coded, it will not be necessary to specify the Projection
datum, etc for this case, since all of those parameters
are determined by the ProjectedCSTypeGeoKey code. Skip to
step 4 from here.

If none of the coded PCS's match your system, then this is a
user-defined PCS. Use the Projection code list to check for
standard projection systems.
Store in: ProjectionGeoKey and skip to Geographic CS case.
If none of the Projection codes match your system, then this
is a user-defined projection. Use the ProjCoordTransGeoKey to
specify the coordinate transformation method (e.g. Transverse
Mercator), and all of the associated parameters of that method.
Also define the linear units used in the planar coordinate
system.
Store in: ProjCoordTransGeoKey, ProjLinearUnitsGeoKey


Now continue on to define the Geographic CS, below.

case GEOCENTRIC:
case GEOGRAPHIC: Check the list of standard GCS's and use the
corresponding code. To use a code both the Datum, Prime
Meridian, and angular units must match those of the code.
查找与GCS相应的基准面，本初子午线和角度单位

Store in: GeographicTypeGeoKey and skip to Step 4.

If none of the coded GCS's match exactly, then this is a
user-defined GCS. Check the list of standard datums,
Prime Meridians, and angular units to define your system.

Store in: GeogGeodeticDatumGeoKey, GeogAngularUnitsGeoKey,
GeogPrimeMeridianGeoKey and skip to Step 4.

If none of the datums match your system, you have a
user-defined datum, which is an odd system, indeed. Use
the GeogEllipsoidGeoKey to select the appropriate ellipsoid

or use the GeogSemiMajorAxisGeoKey, GeogInvFlatteningGeoKey to
define, and give a reference using the GeogCitationGeoKey.
Store in: GeogEllipsoidGeoKey, etc. and go to Step 4.
Step 4: Install the GeoKeyscodes into the GeoKeyDirectoryTag, and the
DOUBLE and ASCII key values into the corresponding value- tags.
Step 5: Having completely defined the Raster & Model coordinate system,
go to Cookbook section 2.6.2 and use the Georeferencing Tags
to tie the raster image down onto the Model space.
20．
Common Examples
UTM Projected Aerial Photo
We have an aerial photo which has been orthorectified and resampled to a UTM grid,
zone 60, using WGS84 datum; the coordinates of the upper-left corner of the image is
are given in eastingnorthing, as 350807.4m, 5316081.3m. The scanned map pixel
scale is 100 meterspixels (the actual dpi scanning ratio is irrelevant).
ModelTiepointTag = (0, 0, 0, 350807.4, 5316081.3, 0.0)
ModelPixelScaleTag = (100.0, 100.0, 0.0)
GeoKeyDirectoryTag:
GTModelTypeGeoKey = 1 (ModelTypeProjected)
GTRasterTypeGeoKey = 1 (RasterPixelIsArea)
ProjectedCSTypeGeoKey = 32660 (PCS_WGS84_UTM_zone_60N)
PCSCitationGeoKey =
Notes:
1) We did not need to specify the GCS lat-long, since the
PCS_WGS84_UTM_zone_60N codes implies particular
GCS and units already (WGS_84 and meters). The citation
was added just for documentation.
不需要说明GCS的经纬度，本身已经包含了这些信息
2) The
structure defined above. At the TIFF level the tags look like
this:
GeoKeyDirectoryTag=( 1, 0, 2, 4,
1024, 0, 1, 1,

1025, 0, 1, 1,
3072, 0, 1, 32660,
3073, 34737, 25, 0 )
GeoAsciiParamsTag(34737)=(
For the rest of these examples we will only show the GeoKey-level
dump, with the understanding that the actual TIFF-level tag
representation can be determined from the documentation.

Standard State Plane
We have a USGS State Plane Map of Texas, Central Zone, using NAD83, correctly
oriented. The map resolution is 1000 meterspixel, at origin. There is a grid
intersection line in the image at pixel location (50,100), and corresponds to the
projected coordinate system eastingnorthing of (949465.0, 3070309.1).

ModelTiepointTag = ( 50, 100, 0, 949465.0, 3070309.1, 0)
ModelPixelScaleTag = (1000, 1000, 0)
GeoKeyDirectoryTag:
GTModelTypeGeoKey = 1 (ModelTypeProjected)
GTRasterTypeGeoKey = 1 (RasterPixelIsArea)
ProjectedCSTypeGeoKey = 32139 (PCS_NAD83_Texas_Central)

Notice that in this case, since the PCS is a standard code, we
do not need to define the GCS, datum, etc, since those are implied
by the PCS code. Also, since this is NAD83, meters are used rather
than US Survey feet (as in NAD 27).
Lambert Conformal Conic Aeronautical Chart
We have a 500 x 500 scanned aeronautical chart of Seattle, WA, using Lambert
Conformal Conic projection, correctly oriented. The central meridian is at 120
degrees west. The map resolution is 1000 meterspixel, at origin, and uses NAD27
datum. The standard parallels of the projection are at 41d20m N and 48d40m N. The
latitude of the origin is at 45 degrees North, and occurs in the image at the raster

coordinates (80,100). The origin is given a false easting and northing of 200000m,
1500000m.
ModelTiepointTag = ( 80, 100, 0, 200000, 1500000, 0)
ModelPixelScaleTag = (1000, 1000, 0)
GeoKeyDirectoryTag:
GTModelTypeGeoKey = 1 (ModelTypeProjected)
GTRasterTypeGeoKey = 1 (RasterPixelIsArea)
GeographicTypeGeoKey = 4267 (GCS_NAD27)
ProjectedCSTypeGeoKey = 32767 (user-defined)
ProjectionGeoKey = 32767 (user- defined)
ProjLinearUnitsGeoKey = 9001 (Linear_Meter)
ProjCoordTransGeoKey = 8 (CT_LambertConfConic_2SP)
ProjStdParallel1GeoKey = 41.333
ProjStdParallel2GeoKey = 48.666
ProjCenterLongGeoKey =-120.0
ProjNatOriginLatGeoKey = 45.0
ProjFalseEastingGeoKey, = 200000.0
ProjFalseNorthingGeoKey, = 1500000.0

Notice that the Tiepoint takes the false easting and northing into
account when tying the raster point (50,100) to the projection origin.
DMA ADRG Raster Graphic Map
The U.S. Defense Mapping Agency produces ARC digitized raster graphics datasets
by scanning maps and geometrically resampling them into an equirectangular
projection, so that they may be directly indexed with WGS84 geographic coordinates.
The scale for one map is 0.2 degrees per pixel horizontally, 0.1 degrees per pixel
vertically. If stored in a GeoTIFF file it contains the following information:
ModelTiepointTag=(0.0, 0.0, 0.0, -120.0, 32.0, 0.0)
ModelPixelScale = (0.2, 0.1, 0.0)
GeoKeyDirectoryTag:
GTModelTypeGeoKey = 2 (ModelTypeGeographic)
GTRasterTypeGeoKey = 1 (RasterPixelIsArea)
GeographicTypeGeoKey = 4326 (GCS_WGS_84)

Unrectified Aerial photo, known tiepoints, in degrees.
We have an aerial photo, and know only the WGS84 GPS location of several points in
the scene: the upper left corner is 120 degrees West, 32 degrees North, the lower-left
corner is at 120 degrees West, 30 degrees 20 minutes North, and the lower-right hand
corner of the image is at 116 degrees 40 minutes West, 30 degrees 20 minutes North.
The photo is not geometrically corrected, however, and the complete projection is
therefore not known.
ModelTiepointTag=( 0.0, 0.0, 0.0, -120.0, 32.0, 0.0,
0.0, 1000.0, 0.0, -120.0, 30.33333, 0.0,
1000.0, 1000.0, 0.0, -116.6666667, 30.33333, 0.0)
GeoKeyDirectoryTag:
GTModelTypeGeoKey = 1 (ModelTypeGeographic)
GTRasterTypeGeoKey = 1 (RasterPixelIsArea)
GeographicTypeGeoKey = 4326 (GCS_WGS_84)
Remark: Since we have not specified the ModelPixelScaleTag, clients
reading this GeoTIFF file are not permitted to infer that there
is a simple linear relationship between the raster data and the
geographic model coordinate space. The only points that are know
to be exact are the ones specified in the tiepoint tag.
这时候不能武断的认为图像空间和模型空间是线性的关系，需要
ModelPixelScaleTag
Rotated Scanned Map
We have a scanned standard British National Grid, covering the 100km grid zone NZ.
Consulting documentation for BNG we find that the southwest corner of the NZ zone
has an easting,northing of 400000m, 500000m, relative to the BNG standard false
origin. This scanned map has a resolution of 100 meter pixels, and was rotated 90
degrees to fit onto the scanner, so that the southwest corner is now the northwest
corner. In this case we must use the ModelTransformation tag rather than the
tiepointscale pair to map the raster data into model space:
ModelTransformationTag = ( 0, 100.0, 0, 400000.0,
100.0, 0, 0, 500000.0,
0, 0, 0, 0,
0, 0, 0, 1)

GeoKeyDirectoryTag:
GTModelTypeGeoKey = 1 ( ModelTypeProjected)
GTRasterTypeGeoKey = 1 (RasterPixelIsArea)
ProjectedCSTypeGeoKey = 27700 (PCS_British_National_Grid)
PCSCitationGeoKey =
Remark: the matrix has 100.0 in the off-diagonals due to the 90 degree rotation;
increasing I points north, and increasing J points east.
Digital Elevation Model
The DMA stores digital elevation models using an equirectangular projection, so that
it may be indexed with WGS84 geographic coordinates. Since elevation postings are
point-values, the pixels should not be considered as filling areas, but as point- values
at grid vertices. To accommodate the base elevation of the Angeles Crest forest, the
pixel value of 0 corresponds to an elevation of 1000 meters relative to WGS84
reference ellipsoid. The upper left corner is at 120 degrees West, 32 degrees North,
and has a pixel scale of 0.2 degreespixel longitude, 0.1 degreespixel latitude.
ModelTiepointTag=(0.0, 0.0, 0.0, -120.0, 32.0, 1000.0)
ModelPixelScale = (0.2, 0.1, 1.0)
GeoKeyDirectoryTag:
GTModelTypeGeoKey = 2 (ModelTypeGeographic)
GTRasterTypeGeoKey = 2 (RasterPixelIsPoint)
GeographicTypeGeoKey = 4326 (GCS_WGS_84)
VerticalCSTypeGeoKey = 5030 (VertCS_WGS_84_ellipsoid)
VerticalCitationGeoKey =
VerticalUnitsGeoKey = 9001 (Linear_Meter)
Remarks:
1) Note the
the DEM posting of the first pixel is at the raster point
(0,0,0), and therefore corresponds to 120W,32N exactly.
2) The third value of the
that a single pixel-value unit corresponds to 1 meter,
and the last tiepoint value indicates that base value
zero indicates 1000m above the reference surface.
垂直坐标系样例及需要注意的地方

21．读写程序 我们的目标只有一个，我们将规范中要求的键值写入文件并能读出，所幸
的事，这些工作别人已经做 了，这就是著名的LibGeoTiff，它是在LibTiff基础
上实现的。
它的主要读写函数原型如下：









GTIFFree(): Free GeoTIFF access handle.
GTIFGetDefn(): Read and Normalize GeoTIFF Definition.
GTIFKeyGet(): Read GeoTIFF GeoKey.
GTIFKeySet(): Write GeoTIFF GeoKey.
GTIFNew(): Create GeoTIFF access handle.
GTIFWriteKeys(): Flush GeoTIFF Keys.
SetCSVFilenameHook(): Override CSV File Searching.
XTIFFClose(): Close GeoTIFF file.
XTIFFOpen(): Open GeoTIFF file.
下面是一个例程makegeo.c：
*
* makegeo.c -- example client code for LIBGEO geographic
* TIFF tag support.
* Author: Niles D. Ritter
* Revision History:
* 31 October, 1995 Fixed reversed lat-long coordinates NDR

#include
#include
#include

void SetUpTIFFDirectory(TIFF *tif);
void SetUpGeoKeys(GTIF *gtif);
void WriteImage(TIFF *tif);

#define WIDTH 20L
#define HEIGHT 20L

void main()
{























char *fname =
TIFF *tif=(TIFF*)0; * TIFF-level descriptor *
GTIF *gtif=(GTIF*)0; * GeoKey-level descriptor *

tif=XTIFFOpen(fname,
if (!tif) goto failure;

gtif = GTIFNew(tif);
if (!gtif)
{


}

SetUpTIFFDirectory(tif);
SetUpGeoKeys(gtif);
WriteImage(tif);

GTIFWriteKeys(gtif);
GTIFFree(gtif);
XTIFFClose(tif);
exit (0);

printf(
goto failure;
failure:




}

printf(
if (tif) TIFFClose(tif);
if (gtif) GTIFFree(gtif);
exit (-1);

void SetUpTIFFDirectory(TIFF *tif)
{













}

void SetUpGeoKeys(GTIF *gtif)
{






GTIFKeySet(gtif, GTModelTypeGeoKey, TYPE_SHORT, 1,
GTIFKeySet(gtif, GTRasterTypeGeoKey, TYPE_SHORT, 1,
GTIFKeySet(gtif, GTCitationGeoKey, TYPE_ASCII, 0,
GTIFKeySet(gtif, GeographicTypeGeoKey, TYPE_SHORT, 1,
GTIFKeySet(gtif, GeogCitationGeoKey, TYPE_ASCII, 0,
GTIFKeySet(gtif, GeogAngularUnitsGeoKey, TYPE_SHORT, 1,
ModelGeographic);
RasterPixelIsArea);
double tiepoints[6]={0,0,0,130.0,32.0,0.0};
double pixscale[3]={1,1,0};

TIFFSetField(tif,TIFFTAG_IMAGEWIDTH, WIDTH);
TIFFSetField(tif,TIFFTAG_IMAGELENGTH, HEIGHT);
TIFFSetField(tif,TIFFTAG_COMPRESSION, COMPRESSION_NONE);
TIFFSetField(tif,TIFFTAG_PHOTOMETRIC,
TIFFSetField(tif,TIFFTAG_PLANARCONFIG,
TIFFSetField(tif,TIFFTAG_BITSPERSAMPLE, 8);
TIFFSetField(tif,TIFFTAG_ROWSPERSTRIP, 20L);

TIFFSetField(tif,TIFFTAG_GEOTIEPOINTS, 6,tiepoints);
TIFFSetField(tif,TIFFTAG_GEOPIXELSCALE, 3,pixscale);
PHOTOMETRIC_MINISBLACK);
PLANARCONFIG_CONTIG);
KvUserDefined);
Used.
Angular_Degree);

}

GTIFKeySet(gtif, GeogLinearUnitsGeoKey, TYPE_SHORT, 1,
GTIFKeySet(gtif, GeogGeodeticDatumGeoKey, TYPE_SHORT, 1,
GTIFKeySet(gtif, GeogEllipsoidGeoKey, TYPE_SHORT, 1,
GTIFKeySet(gtif, GeogSemiMajorAxisGeoKey, TYPE_DOUBLE, 1,
GTIFKeySet(gtif, GeogInvFlatteningGeoKey, TYPE_DOUBLE, 1,
Linear_Meter);
KvUserDefined);
Ellipse_Everest_1830_1967_Definition);
(double)6377298.556);
(double)300.8017);
void WriteImage(TIFF *tif)
{







}
int i;
char buffer[WIDTH];

memset(buffer,0,(size_t)WIDTH);
for (i=0;i

if (!TIFFWriteScanline(tif, buffer, i, 0))
TIFFError(
GeoTiff读取程序设计（初稿，需补充）
TIFF格式中Tag内容与HIPS格式内容对照表：

HPS
备注
TIFF
备注
Description
对文件的一般描述信
息，可以记录不大于
512字 节的说明信息，
比如文件的生成日
期，制作人等。
Artist
图像的作者
Tag =315
Type = ASCII
Copyright
Tag=33432
Type=SCII
DateTime
Tag=306
Type=ASCII
N=20
HostComputer
Tag=316
Type=ASCII
ImageDescription
Tag=270
Type=ASCII
Software
Tag=305
Type=ASCII
N=根据内容来定
Make
Tag=271
Type=ASCII

图像的版权信息
此图像生成的日期及时间

制作此图像的计算机及其操作系
统

生成图像的软件名称及版本号

Samples
文件的宽度
ImageWidth
Tag=256
Type=SHORTLONG
N=1
图像的宽度(像素为单位)
Lines
文件的高度
ImageLength
Tag=257
Type=SHORTLONG
N=1
图像的高度(像素为单位)
Bands
文件的波段数
这部分很值得探讨!!

DataType
数据类型，它 是一个
整型数，描述图像中
一个像素所用的数据
类型。1=字节型(8位),
2=短整型 (16位), 3=整
型 (32位), 4=单精度浮
点 (32位), 5=双精度浮
点 (64位), 12=无符号
短整数 (16位)
这部分很值得探讨!!

InterLeave
数据存储类型。共有三种，BSQ波段连续
存储；BIL行连续存
储；BIP像原连续存
储。标准格式 是BSQ
读取文件后自己设定(可以探讨)

ByteOrder
字节 序，表明本体文
件数据是用主机序还
是网络序存储的，标
准格式应为主机序。
FillOrder
Tag=266
Type=SHORT
N=1
Value=1从左到右
Value=2从右到左
每字节的数据，其位的排列方式
TIFF格式读取程序设计



TIFF图像


0 or 1
Value=0对黑白及灰度图像而言，0为白色
Value=1对黑白及灰度图像而言，0为黑色
BitPerSample=1 黑白图像
BitPerSample=4 16位灰度图像
BitPerSample=8 256位灰度图像

图像数据以R,G,B的方式存储

图像数据采用调色板索引

PhotometricInterpret
ati






2
3
多光谱图像
GeoTiff格式中相关问题探讨
主要是对HIPAS以下内容的考虑：
 MapInformation 地理信息，该项用于描述图像的地理信息
 ProjectInformation 投影信息，该项用于描述图像的投影信息
读取时：

1．本号的详细读取见文章所示，这里不再赘述；
2．坐标系类型判断，具体过程如下：


















3．读取过程中需要读取的Tag如下：
ModelPixelScaleTag
ModelTiepointTag GeoKeyDirectoryTag CS
R -------- OR --------------->M--------- AND ----------> Earth
ModelTransformationTag GeoDoubleParamsTag
GeoAsciiParamsTag
Tag的具体内容如下：
ModelPixelScaleTag = 33550 (SoftDesk)
ModelTransformationTag = 34264 (JPL Carto Group)
ModelTiepointTag = 33922 (Intergraph)
GeoKey DirectoryTag = 34735 (SPOT)
GeoDoubleParamsTag = 34736 (SPOT)
GeoAsciiParamsTag = 34737 (SPOT)
4．
地理坐标系中的需要读入的键如下，针对不同的情况需特殊考 虑（Section
中不同的代号代表不同的数值）：

GeographicTypeGeoKey = 2048 * Section 6.3.2.1 Codes *
指定的地理坐标系类型，需指定其中几个可读取
（需讨论）

GeogCitationGeoKey = 2049 * documentation *
GeogGeodeticDatumGeoKey = 2050 * Section 6.3.2.2 Codes *
指定的Geodetic Datum类型，需指定其中几个可读取，其值（采用格林尼治 PM时）减
去2000即为Geographic的值
（需讨论）

GeogPrimeMeridianGeoKey = 2051 * Section 6.3.2.4 codes *
非DEM
DEM
RasterPixelIsArea = 1 RasterPixelIsArea = 2
GTCitationGeoKey（1026）
描述信息
GTRasterTypeGeoKey(1025)
ModelTypeProjected=1 ModelTypeGeographic = 2 ModelTypeGeocentric = 3
GTModelTypeGeoKey(1024)
GeoTiff图像
Header，确定GeoKey的个数

建议采用
PM_Greenwich =8901（需讨论）

GeogLinearUnitsGeoKey = 2052 * Section 6.3.1.3 Codes *
建议采用
Linear_Meter =9001（需讨论）

GeogLinearUnitSizeGeoKey = 2053 * meters *
GeogAngularUnitsGeoKey = 2054 * Section 6.3.1.4 Codes *
建议采用
Angular_Radian =9101；Angular_Degree =9102（需讨论）

GeogAngularUnitSizeGeoKey = 2055 * radians *
GeogEllipsoidGeoKey = 2056 * Section 6.3.2.3 Codes *
指定椭球体类型，需指定其中几个可读取
（需讨论）

GeogSemiMajorAxisGeoKey = 2057 * GeogLinearUnits *
GeogSemiMinorAxisGeoKey = 2058 * GeogLinearUnits *
GeogInvFlatteningGeoKey = 2059 * ratio *
GeogAzimuthUnitsGeoKey = 2060 * Section 6.3.1.4 Codes *
建议采用
Angular_Radian =9101；Angular_Degree =9102（需讨论）

GeogPrimeMeridianLongGeoKey = 2061 * GeogAngularUnit *

5．投影坐标 系中的需要读入的键如下，针对不同的情况需特殊考虑，如不同
投影类型的定义，需要其中不同的参数， 具体请认真考虑（Section中不同的代
号代表不同的数值）：

ProjectedCSTypeGeoKey = 3072 * Section 6.3.3.1 codes *
指定投影坐标系类型，需指定其中几 个可读取
（需讨论），同时需要考虑目前常用的投
影，如上边Example中所示；

PCSCitationGeoKey = 3073 * documentation *
ProjectionGeoKey = 3074 * Section 6.3.3.2 codes*
指定投影类型，需指定 其中几个可读取
（需讨论），同时需要考虑目前常用的投影，如上边
Example中所示；< br>
ProjCoordTransGeoKey = 3075 * Section 6.3.3.3 codes*
这部分的具体功能不是很清楚，需请卫征参与讨论；
ProjLinearUnitsGeoKey = 3076 * Section 6.3.1.3 codes*
建议采用
Linear_Meter =9001（需讨论）

ProjLinearUnitSizeGeoKey = 3077 * meters *
ProjStdParallel1GeoKey = 3078 * GeogAngularUnit *
ProjStdParallel2GeoKey = 3079 * GeogAngularUnit *
ProjNatOriginLongGeoKey = 3080 * GeogAngularUnit *
ProjNatOriginLatGeoKey = 3081 * GeogAngularUnit *
ProjFalseEastingGeoKey = 3082 * ProjLinearUnits *
ProjFalseNorthingGeoKey = 3083 * ProjLinearUnits *
ProjFalseOriginLongGeoKey = 3084 * GeogAngularUnit *
ProjFalseOriginLatGeoKey = 3085 * GeogAngularUnit *
ProjFalseOriginEastingGeoKey = 3086 * ProjLinearUnits *
ProjFalseOriginNorthingGeoKey = 3087 * ProjLinearUnits *
ProjCenterLongGeoKey = 3088 * GeogAngularUnit *
ProjCenterLatGeoKey = 3089 * GeogAngularUnit *
ProjCenterEastingGeoKey = 3090 * ProjLinearUnits *
ProjCenterNorthingGeoKey = 3091 * ProjLinearUnits *
ProjScaleAtNatOriginGeoKey = 3092 * ratio *
ProjScaleAtCenterGeoKey = 3093 * ratio *
ProjAzimuthAngleGeoKey = 3094 * GeogAzimuthUnit *
ProjStraightVertPoleLongGeoKey = 3095 * GeogAngularUnit *
5．垂直坐标系中的需要读入的键如下，针对不同的情况需特殊 考虑，
（Section中不同的代号代表不同的数值）：

V
erticalCSTypeGeoKey = 4096 * Section 6.3.4.1 codes*
指定垂直坐标系类型，需指定其中几个可读取
（需讨论）；

VerticalCitationGeoKey = 4097 * documentation *
VerticalDatumGeoKey = 4098 * Section 6.3.4.2 codes *
这部分需详细讨论！！！！
VerticalUnitsGeoKey = 4099 * Section 6.3.1.3 codes *
建议采用
Linear_Meter =9001（需讨论）