How to use gis software ENVI? Who will?

ENVI overview

How to use this manual

This manual includes several chapters; Each chapter describes a series of processing programs provided by ENVI. Most chapters follow the menu structure of ENVI. For example, the title of the fourth chapter is "Basic Tools", and the functions it describes can be found under the drop-down menu of basic tools in ENVI. The five appendices aim at: the basic functions of ENVI, file format, spectrum library, map projection and describing the new functions of this version of ENVI. This introductory chapter includes interaction with ENVI graphical user interface (GUI), using ENVI window, and other introductory materials. New ENVI users must read this manual and the attached ENVI tutorial carefully before using it.

For each topic in this chapter, a step-by-step guide to realize it is given after the function description. Parameters are described in the wizard, usually with suggestions and examples. Most functions (except interactive functions) are started from the drop-down main menu of ENVI. A dialog box will appear with parameters that accept user input. Many parameters contain system default values, and some are optional. When this function is running, a processing status window will appear.

Step-by-step wizards for running functions are numbered and displayed in bold. The mouse control menu option appears, and the drop-down menu is displayed in italics. > is used for submenus. Connect. The options in each step are displayed with bullets. Button names are marked with quotation marks, and dialog box titles begin with capital letters. Some dialogs have drop-down menus inside. The options under each drop-down menu are usually described in the section entitled Drop-down Menu.

For example, here's how to median filter files:

1. from the ENVI main menu, select Filters > Convolutions & gt median.

A file selection dialog box will appear, allowing you to interactively change the directory and select the desired input file.

2. Click the file name, and then click OK or Open to select the desired file.

If necessary, any spatial and/or spectral subset is used.

3. When the Convolution Parameters dialog box appears, enter the required filter size in the Size text box.

4. Select the output to "file" or "memory", and if necessary, enter the output file name.

5. Click OK to start processing.

ENVI graphical user interface (GUI)

In order to use ENVI effectively, you must be familiar with the concept of graphical user interface (GUI). GUI provides a graphical way to interact with menus and data. By pointing and clicking or clicking and dragging with the mouse or other designated device, the selection is completed. This manual assumes that you are familiar with these concepts and limits the description to the GUI of ENVI.

ENVI user interface consists of widgets or controls. Widgets are the assembly parts of the GUI-they allow you to interact with the program by clicking, entering text or selecting. Options consist of menus, and menus consist of widgets. Selecting a menu item will pop up a dialog box that requires user input and interaction.

All ENVI operations are activated by using the ENVI main menu, which consists of a series of components arranged at the top of the screen (as shown above) or along the edge (as shown on the right). The layout depends on the configuration parameters selected by the user ("ENVI Configuration File" on page 786). In this document, the menu items on the main menu are called "ENVI drop-down menu" and printed in italics. The following sections describe widgets and menus in more detail.

Mouse button description

ENVI mentioned the use of the three-key mouse mark throughout the article. Without a mouse with at least three buttons (or the method of simulating three buttons) and appropriate mouse driver software, the part ENVI needs the third mouse button to complete will not run. ENVI for Macintosh and ENVI for Windows include three-button simulation. To simulate pc mouse:

For Windows:

The simulation of the middle key is realized by pressing the "Ctrl" key and the left mouse button.

For Macintosh:

A single button of the Apple mouse is used as the left mouse button.

The simulation of right click is realized by pressing the "Apple" key and the mouse button.

The simulation of the middle key is realized by pressing the "Option" key and the mouse button.

pull-down menu

The drop-down menu consists of menu items and additional buttons, which will only appear when the left mouse button is pressed on the menu item. The drop-down menu is used to select a single ENVI menu item or operation from the cascade selection list. A menu item with an arrow after its name contains a submenu that appears if it is selected. A dialog box will pop up after the menu item name with "...", asking for additional user interaction. Menu items without dots directly perform the specified operation. You can select the drop-down menu by clicking and holding down the left mouse button on the menu item, or drag the drop-down menu and release the mouse button when selecting or highlighting the appropriate menu item.

Figure 1- 1: drop-down menu.

menu bar

The menu bar is just a set of drop-down menu labels at the top of other widgets. Use the drop-down menu above to make a selection. All menu bars have a file drop-down menu where you can choose Cancel to close the widget.

Figure 1-2: menu bar.

Button component

The button part (called "button" throughout the document) consists of a rectangle containing a text label describing the function or operation of ENVI. Click the text in the rectangle with the left mouse button to perform the function corresponding to the button.

Toggle buttons and radio buttons

Toggle buttons are round or diamond buttons with externally related text. Click the button or related text to switch between the on and off buttons. Some toggle button groups are radio buttons, and only one button can be selected at a time. At this point, selecting one button will cause all other selected buttons to be cancelled.

Figure 1-3: An example of a dialog box with widget types.

Check box (check box)

Check boxes are similar to toggle buttons. Click on the box to select an option, and the box is marked with an "X". With this widget, you can select multiple options at once.

Arrow toggle button

The arrow toggle button is a bitmap button, which consists of two arrows in a rectangular button box related to text. Click the button to switch the display between the two possible options. The selected option is displayed in the relevant text box.

Editable text widgets and label widgets

Editable text parts are rectangular boxes that provide users with keyboard input. ENVI, when many editable text widgets first appear, they contain default text strings. You can edit the content of a text widget by clicking the left mouse button in the box to mark the position where you want to insert the text, and then entering the text with the keyboard.

Label widgets consist of text used to mark other widgets. Cannot edit the label widget.

List widget

The list widget consists of a rectangular box with a list of available options. Click on the text option and select the left mouse button. If more options can be displayed within the size defined by the list widget, the vertical scroll bar to the right of the widget allows you to scroll up and down the list until you see the desired option. If the UNIX platform is used, a second scroll bar (horizontal scroll bar) will appear when the list option is wider than the width defined by the list widget. To select options in the list widget, you have the following options:

To select a single option, click the left mouse button on the option.

To select a set of consecutive options in the list, click the first item, hold down the shift key on the keyboard, and then click the left mouse button on the last item to select all the options in the middle, or click and drag down to the last item in the range.

To select multiple discontinuous options in the list, click the left mouse button on the required item, hold down the "ctrl" key on the keyboard, and then click the left mouse button on other required items. To deselect from a set of selected options, use the same method.

Widgets for drawing.

The widget used for drawing consists of a rectangular area that displays ENVI images and graphics. Move the mouse cursor to the drawing widget and click the left mouse button, middle mouse button or right mouse button to perform various tasks of ENVI respectively (depending on the function of the window). You can resize the drawing widget: click a corner of the widget, press the left mouse button, and then drag it to the desired window size.

Arrow increment button

The arrow increment button is an editable text widget with two small arrows. You can use keyboard input to change the value in a text widget, or use arrows to increase or decrease the value of a parameter. Click the left mouse button on the up/down arrow to increase/decrease the value of the text box by 1. Click the middle mouse button on the up/down arrow to increase/decrease the value of the text box by 5. Clicking the right mouse button on the arrow will reset the parameters to their initial values.

Figure 1-4: widgets for drawing

Figure 1-5: an arrow increment button

Slider widget

The slider widget consists of a tabbed toolbar, an additional scrolling toolbar, and (especially) text values near the scrolling toolbar. Click and hold down the left mouse button until you drag it to a new position to change the value of the slider. Depending on the operating system, when the slider moves, its value can be displayed continuously or updated immediately after releasing the slider button.

Figure 1-6: A slider component.

ENVI dialog box foundation

Your interaction with ENVI will often be conducted through the dialog box. These dialogs are composed of different widgets, and will "pop up" when ENVI needs your input to continue this function (see figure 1-3). They are usually activated by selecting a drop-down menu item followed by "...". In the dialog box, you can find various widgets, including default values preset by the system. In the dialog box, the purpose of displaying these values is to allow you to select them according to your own needs.

Most dialog boxes contain buttons labeled OK and Cancel. Click the "OK" button and tell ENVI to pass the input to the function. Click Cancel to exit the dialog box without starting the function.

General concept of image display

The image display in ENVI consists of a set of three different image windows: main image window, scrolling window and zoom window. ENVI image shows an example as shown in figure 1-7. The single image window of the display group can be scaled and placed anywhere on the screen. You can start the display of multiple images by selecting Start New Display from the display control submenu under the file drop-down menu of ENVI, or by clicking "New" in the existing band list (see "Available Band List" on page 47).

Main image window

The main image window consists of a part of an image displayed at full resolution. This window will start automatically when the image is loaded for the first time. The starting size of the window is controlled by the parameters set in the envi.cfg configuration file (see "envi configuration file" on page 786). It can also be scaled dynamically (see "Resizing Windows" on page 45). ENVI allows loading multiple main image windows and corresponding scrolling and zooming windows.

Function menu in the main image window

Click the right mouse button in the main image window to open and close the hidden submenu. "Functions" menu controls all ENVI interactive display functions, including: image linking and dynamic superposition; Spatial and spectral profiles; Contrast stretching; Color map; Interactive functions such as ROI definition, cursor position and value, scatter plot and surface plot; Overlay (overlap) such as notes, grids, image isolines and vector layers; Animation and display functions.

Scroll window

The scrolling window is a small image display window, which displays a large image with subsampled resolution. The location and size of the scrolling window are initially set in the envi.cfg file and can be modified. The scrolling window will only appear when the image to be displayed is larger than the image that can be displayed at full resolution in the main image window. You can dynamically scale it to any size until it is displayed in full screen (see "Resizing Windows" on page 45). When you use this option, the resampling factor will automatically change to fit the new image size. The resampling factor appears in parentheses in the title bar of the scrolling window. For a large image resampled in the scrolling window, you can enlarge the area and reduce the resampling factor. Multiple scrolling windows may appear, and each window corresponds to a loaded main image window.

Figure 1-7: an ENVI display group. These windows can be placed anywhere on the screen.

Zoom window

The zoom window is a small image display window that displays a part of the main image window by using pixel replication with a user-defined zoom factor. The size and location of the zoom window and the default zoom factor of the system are initially set in the envi.cfg file and can be modified by the user. The zoom window provides unlimited zoom function, and the zoom factor is displayed in brackets in the title bar of the window. The zoom window can be dynamically adjusted to the size available on the screen (see "Resizing the window" on page 45). Multiple zoom windows can be displayed, and each window corresponds to a loaded main display window.

Resize the window

Many ENVI windows can be dynamically resized to full screen. This includes image display, vector window and all auxiliary windows except scatter plot and animation window. The adjustment of the window size is realized by clicking on one corner of it with the mouse pointer and dragging it to the required image size.

Current display

Only one displayed image (the main image, the combination of scrolling and zooming windows) is "active" at a time. The active display is the display group that will load the next image. Set the active display by entering the appropriate number of displays in the existing band list. Please note that it is not necessary to activate the monitor to apply the functions, and using these functions will not activate the monitor.

Auxiliary window

ENVI image display can have many related auxiliary windows. These windows are usually started by the interactive display function of ENVI, and can include X, Y, Z and any section, histogram, scatter plot, surface diagram (perspective view) and animation window. They all belong to a specific image display group. Multiple monitors can have their own independent auxiliary window groups.

Vector display list

The vector display list consists of the vector window and its related "Vector Window Parameters" dialog box. An example of a vector display group is shown in figure 1-8. Like the image display window, the vector window can be resized and placed anywhere on the screen (see Vector Layer).

Figure 1-8: an ENVI vector display group

Data management

ENVI provides many tools for managing images, vector data, dialog boxes and single windows. These tools are discussed in the following sections.

Available band list

The list of available bands is used to access ENVI image files and the control panel of individual image bands of these files. Whenever an image file is opened, whether the image is displayed or not, the existing band list will appear in its own dialog box, which contains the existing image band list of all open files and any memory data items (calculated in memory but not saved). If multiple files are opened, all bands of all files will be listed in order, with the band of the most recently opened file at the top of the list. The existing band list is used to load grayscale and color images into the active display, open and close files, or delete individual bands from the memory (see "Available Band List" on page 97).

Available vector list

The list of available vectors contains a list of all vector files in memory that can be displayed in the image display window or the vector display window. After loading, all vector layers read into memory will be listed in order, with the latest vector at the top of the list. You will use the existing vector list to start the vector display group and delete the vector layer from the memory (see "Available Vector List" on page 1 14).

Browse the directory listing and geobrowser.

Browse the directory list to list all ENVI files in the selected directory, print file information, allow the selected file to be opened, and start the Geo-Browser file display. Geobrowser marks the location of all geocoded data with red flags on the map of the world. Users can zoom the map and click the red mark to select the required file (see "Scan Directory List" on page 93).

Open file list

Open file list is a tool for managing ENVI image files. It lists the names of all currently open files and all memory data items. Select a file name, and all the known information of the file will be listed. This includes parameters such as full path and image name; Number of lines, sample points and strips; Title size; File type; Data type; Cross; Byte order of data; And whether geographic coordinates are used for positioning and whether the wavelength is associated with the band. Options include deleting memory data items, closing or deleting individual files, and writing memory calculation results to disk files. These operations can optimize the use of system memory (see "Open File List").

Widget controller list

The list of widget controllers can be found under the drop-down menu of ENVI system. It lists all the main ENVI windows, including: main image, scrolling and zooming windows, all auxiliary windows, and other windows and dialogs used in many ENVI interactive functions. Widget controller list can call any window or dialog box to the foreground by clicking the name (see Widget Controller List). For example, if you need to access an existing band list, but it is hidden behind your image, the steps are as follows:

1. select system > widget controller list.

2. Click "Available Frequency Band List".

ENVI processing status window

When the calculation is executed, most ENVI functions display the processing status. After the function is started (usually by clicking the OK button), a standard status window will appear immediately. The title of the window matches the function being executed and shows whether the result is stored in memory or in an output file. When processing data, the slider marked "%Complete" will be updated in time. The text box labeled "Inc:" shows the size of each data processing increment, which is based on the slice size (see "Slicing Operation" on page 50). Function automatically determines the size of the processing increment. For example, the value "16.67%" shown in figure 1-9 indicates that the data will be processed according to several tiles, and each tile contains 16.67% of the total data (when displayed on the slider toolbar, the increment of the score will be rounded to the nearest integer).

Figure 1-9: processing status window.

pay attention to

If the increment is less than 100%, you can use the Cancel button to terminate the processing. At this point, the function will be interrupted when the next increment occurs. If the increment is equal to 100%, the function cannot be interrupted.

memory management

ENVI allows processing large data sets, even using the marginal memory configuration on the machine. For example, a typical processing task usually uses a data set larger than 200Mb on a machine with only 16Mb of physical memory. If there is not enough memory to handle a task, the data set will be divided into manageable parts, processed in memory, and then written to a disk file. On high-end machines, you can process large data sets in memory without creating disk files.

Tiling operation

ENVI allows the use of "tiling" to handle large images and control the use of system memory. Tile is a piece of data read from disk or memory in segments. In ENVI, the size of a single tile is controlled by setting the required value in ENVI configuration file (see "ENVI configuration file" on page 786).

For images stored in BSQ (in band order), each slice is a spatial subset of a single band. For images stored in BIL format, each collage is a line of all bands of the image. For BIP format, each tile is all pixels of all bands in the image. Tiling is usually transparent to users, and ENVI uses it to ensure that the limitation of hardware memory will not affect the processing (see "Profile Details" on page 786 and "Additional Cache Information" on page 793).

Comparison of file and memory functions

For a system with a large random access memory (RAM), effective image processing can be performed without repeatedly storing the intermediate processing results in a disk file. For most functions, ENVI allows processing results to be written to disk files or stored in system memory.

pay attention to

If you choose to use memory items, please save the results to a disk file regularly.

ENVI file format

ENVI supports several image file formats, which are described below. This section also involves the format of ENVI title file, the principle of file naming, and the issue of cross-platform portability.

ENVI image file

ENVI uses a general raster data format, which consists of a simple "flat binary file" and a corresponding small ASCII (text) title file. This method allows ENVI to flexibly use almost any image format, including those with embedded file title information. The original format of all data types (byte, integer, long integer, floating point, double precision or complex number) is supported. General raster data is stored in a binary byte stream according to BSQ, BIP or BIL format (see "ENVI file format" on page 795).

BSQ (with sequential format)

The simplest format is data in BSQ format. Each row of data is followed by the next row of data in the same spectral band. This format is most suitable for accessing the space (x, y) of any part in a single spectral band.

BIP (pixel-by-pixel interleaved format)

Images stored in BIP format store all the bands of the first pixel in sequence, then all the bands of the second pixel, then all the bands of the third pixel, and so on, and access them in an interleaved manner until the total number of pixels is reached. This format provides the best performance for accessing the image data spectrum (z).

BIL (stripline crossing format)

Images stored in BIL format first store the first line of the first band, then the first line of the second band, and then the first line of the third band, and are interleaved until the total number of bands. Subsequent rows of each band are staggered in a similar manner. This format provides a compromise between spatial and spectral processing, and is the recommended file format in most ENVI processing tasks.

ENVI header file

A separate ENVI text header file provides information about image size, embedded header file (if any), data format and other related information. ENVI header files contain information for reading image data files, which are usually created when ENVI first accesses the data files. The necessary information can be created automatically through interactive input or file intake, and can be edited and modified later. If necessary, you can use a text editor outside ENVI to generate an ENVI header file (see "ENVI header file format" on page 797).

ENVI file naming convention

ENVI file processing program design is extremely flexible. ENVI software name file has no restrictions except extension. Hdr is used for header files. For ease of use, some ENVI functions pre-install a file list with a specific extension. The following table shows these extensions. When running ENVI, they should be used consistently to achieve the highest file processing efficiency. This does not prevent you from using another file name if necessary.

File type extension

ENVI image is undefined.

ENVI bad line list. bll

Compressed data products. Cytidine 5- diphosphate (short for cytidine 5-diphosphate)

ENVI header file. Direct hot rolling system

ENVI calibration factor. China Textile Apparel Exhibition

ENVI PPI counting file. (cannot) can't

ENVI density slice range file. Daily Service Report (daily service report)

ENVI vector file. Ethanol capacity fraction

ENVI band mathematical or spectral mathematical expression. experience

ENVI tape script. fmt

ENVI grid file. grd

ENVI filter kernel. nucleus

ENVI mapping key. key

ENVI outline hierarchy file. Lev (basic unit of currency in Bulgaria)

ENVI lookup table. lut

ENVI mosaic template file. mos

ENVI n-D visualizer status. ndv

ENVI GCP file. Hong Kong Police Training School (abbreviation for Police Training School)

ENVI area of interest. Return on investment)? and profit Rate of Interest.

ENVI statistical report. Textfile (textfile)

ENVI spectrum library. sli

ENVI statistics file. Temporary use permit for radio station

ENVI surface view path file. patch

JPL AIRSAR compresses Stokes matrix radar data. stk

ENVI vector template file. vec

Table 1- 1: ENVI file type

Cross-platform file portability

An additional factor to consider when using ENVI naming files is cross-platform portability. Add one. Hdr to file name on UNIX system. On Windows systems,. Hdr replaces the current extension. This is important for maintaining image files and their corresponding (.hdr) header files. For example, a UNIX image file named image_ 1.img has image_ 1.img.hdr as its corresponding header file. The Windows image file named image_ 1.img has image_ 1.hdr as its corresponding header file. Under Windows, two images image_ 1.img and image_ 1.dat will have the same header file name image_ 1.hdr. If the two images are different in size and characteristics, ENVI will have problems. Under UNIX, the same two files will have corresponding header file names image_ 1.img.hdr and image_ 1.dat.hdr, so they will not be confused. If there is a problem with the cross-platform portability of images, the simplest solution is to use only 8 characters and not use the extension to name image files. In this way, the image file image_ 1 has the same header file name (image_ 1.hdr) under UNIX and Windows. In addition, before moving images from UNIX system to Windows system, images and header files can be renamed according to Windows convention.

ENVI supported input file formats

ENVI supports the input file format shown below. For more information about these formats, see "Opening Image Files" on page 60, "Opening External Files" on page 64 and "Opening Vector Files" on page 83. ENVI supports many input file formats:

Low plane binary file:

● BSQ (sequenced format)

● BIL (band interleaving in line format)

● BIP (band interleaving by pixel format)

● Remote sensing format file:

● ADRG ● Geography

● AIRSAR ● HDF

● ArcView grid (. HDF MAS-50

● ATSR ● JERS

● AVHRR ● MRLC

Caderousse nitf

● CIB ● NLAPS CD

● DMSP (NOAA) ● PDS image

● DOQ (United States Geological Survey) ● Radar satellite

* EOSAT FAST IRS- 1●sea wifs

● EOSAT FAST TM ● SIR-C

● ERS ● SPOT CD

Esa earth resources satellite TM ● TIMS

● ESA Sharp TOPSAR

● GeoSPOT

● Image processing format

● ArcView grid (. Bil●ER mapper

● ERDAS 7.5(。 Local area network) ● PCI (. pix)

● ERDAS 8.x(。 img)

● Other common image formats:

● ASCII ● PICT

● BMP ● SRF

● GIF ● TIFF (GeoTIFF)

● HDF ● TIFF world archives (. tfw)

● JPEG ● XWD

● Digital elevation format

● USGS Deutsche Mark ● USGS SDTS Deutsche Mark

● DMA DTED

For more information, see "Digital Elevation Format" on page 79.

● Vector file:

●ARC/ information exchange● MapInfo exchange

format

● ArcView shape file ●DGN Microstation

●DXF●DLG USGS

Envi vector file (. Evf) ● DLG station of USGS in SDTS format

ENVI supported output file formats

ENVI supports the output file format shown below. For more information about these formats, see "Display Output Options" on page 3 10, "Output Data to an External File" on page 384, and "Vector Window Parameters Dialog Box" on page 279.

● ENVI plane binary file: