Techniques | Yale Center for Geospatial Solutions

Tasseled Cap Transform for Landsat (8) OLI

ENVI can calculate the Tasseled Cap Transformation of Landsat MSS, TM, and ETM sensor data. The transforms for each sensor produce a different number of bands. The MSS transform produces a four-band output file with bands identified as: Soil Brightness Index, Green Veg Index, Yellow Stuff Index, and Non-such Index. The TM transform produces a three-band output file with bands identified as: Brightness, Greenness, and Third. The ETM transform produces a six-band output file with bands identified as: Brightness, Greenness, Wetness, Fourth, Fifth, and Sixth. The user is encouraged to cons

Programming in ENVI

Often we need to apply the same set of functions to multiple files. For example, you may want to import a collection of Landsat images, apply radiometric calibration to Top of Atmosphere reflectance, and subset the images to your study area. Or perhaps you want to import and stack MODIS day-time Land Surface Temperature (23 per year) for five years. Then repeat this process for the night-time temperatures. These can be done individually in ENVI but may take a lot of time and effort .

How to capture Google Earth images for use in ENVI

There are times when you may want to capture high resolution screenshots form Google Earth to use in ENVI software. This could be for background display, ground truthing, or viewing historical imagery. Basically in Google Earth you will navigate to the area you wish to capture and place markers in each corner. After saving the image you will use these corner markers to georeferenced your image in ENVI or ArcMap.

Calculating solar radiation using Solar Analyst

One important contribution to the understanding of a landscape is the incoming solar radiation, or insolation, that is available at the surface. While one could use the global average of 1366 watts/m², actual values are generally much lower. On a global scale the controlling variables are the latitude, distance from the sun, and time of year. At the local level elevation, slope and aspect are major factors in determining the amount of energy available. You will need ArcGIS version 9.2 or greater with the Spatial Analysis extension.

Converting ENVI classification data to an ArcGIS shapefile

Once you have created a landcover classification in ENVI you may wish to view or work with these data in ArcGIS. If you include a file extension of “.DAT” as part of the filename you can open this file directly in ArcGIS. For example, you can open the file MyClass.dat in ArcGIS and you will see the classified image with the colors that you have specified.