Envi setup head

Reference : Gruber, M. The orthophoto did not have any wavelength information, so we manually added the peak wavelengths for each band to the ENVI header file. For the near-infrared band, we used the center wavelength nm. The custom location is saved under the Placemarks menu. When you move to another area in the image, you can go back to the saved location by clicking Placemarks and selecting it from the list; for example:. As you move the cursor around the image, the latitude and longitude coordinates of the cursor location are displayed in the Status Bar at the bottom of the ENVI application.

The Status Bar contains three horizontal segments. By default, the first left segment displays geographic coordinates, and the second segment displays the map projection details for the image.

The third segment is blank. The following figure shows an example of the first two segments:. You can choose to display different types of image information in each segment by right-clicking and selecting an option. Now that you understand some basic exploration techniques, let's learn how to work with multiple data layers and views. The Layer Manager shows the datasets that are displayed in the Image window. Since there is only one view you will learn about multiple views later , the image layer is listed under one View category.

For images, it also lists the available bands. Since the associated header file for this image CentralParkOrthophoto.

In the Data Manager, you can see that the image contains a fourth band Band 4: Near infrared. Having two views provides a convenient way to compare images side-by-side. However, notice that when you zoom or pan in one view that the other view remains the same. You will need to establish a geographic link between the views. Metadata provide details about a dataset in general such as its source, data type, and projection.

Follow these steps to view the orthophoto metadata:. The Basic Stats section shows the actual minimum, maximum, and mean data values in each band, along with the standard deviation. If an image is georeferenced to a standard map projection as with this orthophoto , you can measure the distance between objects. Next, you will learn how to modify the display properties of the image and add grid lines to the image. Steps like these are normally taken to create screen captures or full-resolution presentations that you can share with others.

They do not modify the original image data in any way. You can apply one of 10 quick stretches to the image using the Stretch Type drop-down list in the toolbar. By default, no stretch is applied to this orthophoto. You can click the Reset button next to each slider to go back to the default value.

To the left of the Stretch Type drop-down list are three buttons that let you choose how the stretch is computed.

By default, the Stretch on Full Extent button is enabled, which means the selected stretch is based on the histogram of the entire image. In the following steps you will create a screen capture also called a chip of the contents of the Image window. It also captures any annotations that are visible in the view.

The Chip View to options are best used for taking a quick snapshot of the contents of a view; for example, to send via e-mail or to embed in a PowerPoint presentation. However, these are not ideal options when creating publication-ready images, posters, or PDF files.

In these cases, you will likely want to create an output image that preserves the original resolution of the input image. You will learn how to do this next. It preserves any annotations and image enhancements you add; however, it does not preserve the north arrow.

At the heart of ENVI is a wide variety of analytics that process image data into information used for vegetation studies, land use monitoring, defense and intelligence, and other applications. Examples of analytics include change detection, feature extraction, and classification. All of the analytics are available from the Toolbox, located on the right side of the ENVI application. The ENVI Toolbox also contains tools used for image preprocessing, raster operations, geographic positioning, and mosaicking.

Tools are organized by folder according to different applications. In this section you will run two different tools while learning about masks and regions of interest ROIs. Spectral indices are combinations of spectral reflectance from two or more wavelengths that indicate the relative abundance of a feature of interest. To ensure the most quantitatively accurate results, the input image used for spectral indices should be in units of reflectance and corrected for atmospheric effects.

You do not need to perform those steps in this tutorial. However, we provide a region of interest ROI file that you can use to mask out water from the image, before creating spectral index images.

The following steps provide an example. It requires an input image that only has three bands in the order of red, green, and blue. Since the orthophoto has four bands, you must define a spectral subset that only includes the first three bands. Search Results. This tutorial provides a comprehensive introduction to using ENVI. File Description CentralParkOrthophoto.

Technical Notes: The orthophoto was originally acquired from an UltraCam Eagle digital camera, which has the following wavelength ranges for visible to near-infrared bands: Blue: - nm, peak at nm Green: - nm, peak at nm Red: - nm, peak at nm Near-infrared: - nm Reference : Gruber, M. Click the Open button in the toolbar. The toolbar is located along the top of the ENVI application: When the Open dialog appears, navigate to the location where you saved the tutorial data.

Select CentralParkOrthophoto. Press the F12 key on your keyboard to view the full extent of the image. This is a true-color image that shows natural and man-made features. A separate window appears with a map of the image location.

The cyan-colored box indicates the extent of the image, and the dot in the middle indicates the image center. It contains several softball fields, ponds, and an amphitheater.

The large building in the lower-right corner is the Metropolitan Museum. Explore the image using these techniques: If your mouse has a scroll wheel, use it to zoom in and out of the image. If not, press the F9 key to zoom in or the F10 key to zoom out in fixed increments.

The zoom level is displayed in the toolbar; for example: To zoom into a specific area, click the Zoom button in the toolbar and draw a box around the area to zoom. To pan around the image, click the Pan button in the toolbar.

Left-click and drag the mouse to pan. Or, click and drag the middle mouse button or scroll wheel. To rotate the image, click the Rotate View button in the toolbar. Left-click and drag the mouse to rotate. Or, select a rotation angle from the drop-down list in the toolbar. In the New Placemark dialog, enter a name for the location and click OK ; for example: The custom location is saved under the Placemarks menu.

When you move to another area in the image, you can go back to the saved location by clicking Placemarks and selecting it from the list; for example: As you move the cursor around the image, the latitude and longitude coordinates of the cursor location are displayed in the Status Bar at the bottom of the ENVI application.

The following figure shows an example of the first two segments: You can choose to display different types of image information in each segment by right-clicking and selecting an option. Right-click in the first left segment and select Raster Data Values.

The Layer Manager is located near the upper-left corner of the application. A small yellow overview window is displayed in the upper-left corner of the view. Pan around the image. The red box in the overview window shows the extent of the current view location, relative to the entire image. Uncheck the Overview option to hide the overview window. Click the Detach button in the Layer Manager to detach it from the application. It becomes a floating window that you can resize and move to a different location.

Click the Data Manager button in the toolbar. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Helping communities build their own LTE networks. Podcast Making Agile work for data science. Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Related Hot Network Questions. Question feed.

Stack Overflow works best with JavaScript enabled. Use this keyword to specify a named variable that contains a string array of spectral library names. You should set this keyword only for a spectral library file. Use this keyword to specify a named variable with the angle of the sun in degrees from due north in a clockwise direction. Use this keyword to specify a named variable with the angle of the sun in degrees above the horizon.

Georeferenced images do not use this value. Instead, they use the pixel size and units contained in the map information structure.

Use this keyword to specify a named variable that contains a value indicating the wavelength units. The valid values are as follows:. Use this keyword to specify an array of wavelength values. The number of elements in this array is equal to the number of bands. Set this keyword to write an output header to disk. The default is to not write an output header. Use this keyword to specify the x starting sample for the first pixel in the file.

The default is 0. Use this keyword to specify the y starting line for the first pixel in the file. Use this keyword to specify a two-element array of long integers representing the x and y window size in pixels for the Z Profile. The window size must be a value of 1 or greater. The Z Profile is formed from the average of the profiles within the specified window.

The default window size is [1, 1]. Use this keyword to specify a two-element string array with the x-axis and y-axis plot titles. Search Results. Use this procedure to create header information for a disk file. If the offset is negative, a minus symbol - precedes the value.