3. Basic Information
An interactive computer language, similar to Matlab.
Command line input, execute and output results immediately, like interpret language.
Programming language, can be used to write procedures, functions, and programs
(scripts), like C or Fortran.
Expandable with user-supplied packages.
Oriented toward use by scientists and engineers in the analysis and visualization
of multi-dimensional data sets.
Platform Independent: Unix, linux,Windows, Macintosh
Two capabilities which are essential for modern data analysis: interactivity and
graphics display.
4. Application
Advantages
Image Processing
Application related to ENVI
Matrix Operation
A strong complementary tool to ArcGIS Raster Analysis
Mostly used in Astronomy and Medical Imaging
Disadvantages
NOT open source (owned by ITTVisual Information Solutions)
NOT as popular as Python (Personal view)
5. User Group
气象系统
国家卫星气象中心、广西气象减灾研究所、气象局兰州干旱气象研究所、国家气象局气象中心、深圳
市气象服务中心、中国气象局气候中心气候系统诊断预测室、湖北省气象局武汉区域气候中心、国家
气象局气象卫星中心、云南气象局、北京气象局、广东气象局、中国气象局北京城市气象研究院、福
建省气象科学研究所、西藏气象局、青海气象局…
海洋系统
国家海洋局第二海洋研究所、厦门海洋与渔业局、国家卫星海洋应用中心、青岛海洋一所、东海水产
研究所、国家海洋信息中心、国家海洋环境监测中心、上海河口海岸科学研究中心…
水利系统
珠江水利委员会、长江水利委员会、长江科学院、黄河水利委员会、南京水利科学研究院、新疆塔里
木河流域管理局信息所、…
国土、测绘系统
云南省基础地理信息中心、陕西省国土资源厅信息中心、中国测绘科学研究院 、深圳城市管理局、国
家基础地理信息中心 、浙江省国土资源厅信息中心、航遥中心、黑龙江工程学院测绘工程系…
Obtain from ESRI China
6. User Group
地震、地质系统
地震局地质所、贵州师范大学中国南方喀斯特研究院、东北大学资源与土木工程学院地质系、新疆
地矿局信息中心、中石油管道分公司管道科技研究中心、中石油勘探研究院测井所、 核工业北京地
质研究院 、中国石油勘探开发研究院、西安煤航、核工业西南物理研究院、新疆地矿局信息中心…
交通、环保系统
北京市环保监测中心、人民大学环境学院、苏州科技学院 环境科学与工程学院、成都信息工程学院
环境工程学院、交通部天津水运工程研究所、铁四院、…
农林系统
国家林业局、中国林科院、西北林业调查规划设计院、河南林业调查规划院、福建林科院、中国农
业科学研究院植物保护研究所、陕西省气象局农业遥感信息中心、新疆农业大学草业与环境科学学
院、 湖南农业大学 、河南农业大学、东北林业大学、内蒙古农业大学、南京农业大学、扬州大学农
学院、华中农业大学、北京市农林科学研究院、…
Obtain from ESRI China
9. Syntax of IDL
DataType
1 Byte nB 8-bit unsigned
2 Integer n 16-bit signed
3 Longword nL 32-bit signed
4 Floating Point n.n 32-bit (+1038)
5 Double-Precision n.nD 64-bit (+1038
)
6 Complex COMPLEX(n.n,n.n) real/imaginary pairs
7 String 'ssss' 0-32k in length
8 Struct User-defined Structure
9 D-P Complex DCOMPLEX(n.n,n.n) real/imaginary pairs double-precision
10 Pointer Pointer
11 ObjRef Object Reference
12 Unsigned Int nU 16-bit unsigned
13 Unsigned Long nUL 32-bit unsigned
14 64-bit Long LONG64(n) 64-bit signed longword
15 64-bit Unsigned Long ULONG64(n) 64-bit unsigned longword
10. Syntax of IDL
help, variable_name
Print out the type of variables, and values for simple types.
If variable_name is a structure, use keyword /struct to print out the names of its tags.
It can also be used to print information about currently compiled procedures and/or functions,use
keyword /func and /proc
print, variable_name1, variable_name2, …
Print out the value of variables.
For arrays, the values of all elements will be printed out.
plot, x_variale, y_variable
Plot y_variable as a function of x_variable
variable = fltarr(column_number, row_number)
Generate a 2-D floating point array with the specified numbers of columns and rows.
It can take more input parameters to generate multi-dimensional arrays.
11. Syntax of IDL
Logical expressions
variable1 gt variable2, will return a scalar or an array where the elements are 1 if the corresponding
elements of variable1 is greater than variable2, or 0 if variable1 is not greater than variable2.
Other similar operators are: ge (greater or equal), lt (less than), le (less than or equal), eq
(equal), ne (not equal)
if expression then begin
statements
endif else begin
statements
endelse
for variable=init, limit , increment do begin
statements
endfor
While, Repeat…
13. Further Topic to Explore
IDLWidgets
Object-oriented programming
(IDLffShape class)
Standalone Distribution
(IDLVirtual Machine + *.sav)
14. Work with ENVI
We can use build-in ENVI functions to do what we want to do with images
ENVI_OPEN_DATA_FILE
ENVI_GET_DATA
ENVI_GET_PROJECTION
……
15. Work with ENVI
RSIES:A Software Development Project that combine ArcGIS and ENVI
Core ActiveX Control: COM_IDL_connectLib 1.0 Type Library
Use COM_IDL_connectlib to execute IDL Command in C#
18. Work with ENVI
The Computation of Night Light Development Index:A Pixel-based Analysis
Convert each polygon in shape file into Region of Interest (ROI);
Extract image data of light and population using ROI;
Compute Index using the same calculation procedure of Gini coefficient.
21. Resources
Always refer to IDL help
IDL Code Library
http://www.exelisvis.com/Learn/CodeLibrary.aspx
ENVI/IDL Chinese Forum
http://bbs.esrichina-bj.cn/ESRI/forumdisplay.php?fid=28