MicroImages, Inc. • TNTgis - Advanced Software for Geospatial AnalysisVoice (402)477-9554 • FAX (402) 817-0151 • email info@microimages.com • web www.microimages.com • September 2014

Spatial Display

Image Band Correlation

Image Band Correlation window showing correlation plot for two bands ofa Landsat scene extract. The RED band is the X axis and the PHOTO_IRband is the Y axis. (over)

Zoom and Reposition

You can investigate linear trends within thescatterplot using the Line tool. Use this tool todraw, reposition, and resize a two-point line any-where within the scatterplot. As shown in theillustration on the reverse, the equation of this lineis automatically shown at the top of the scrollabletext pane at the bottom of the window.

Line Tool

You can resize the Image Band Correlation win-dow to change the size of the drawing area used toshow the correlation scatterplots. The zoom iconbuttons shown to the left also allow you to changethe zoom level of the scatterplots. You can zoomin, zoom out, show the full dimensions of eachscatterplot, or zoom to show the maximum detailof the scatterplots.

If you have zoomed in, the Reposition tool allowsyou to drag a scatterplot around within its rectan-gular frame to view the desired portion of the plot.

You can use the Image Band Correlation window in the Dis-play process in TNTmips to explore the distribution ofspectral values between one or more pairs of image bands.Open the Image Band Correlation window from the DisplayManager by right-clicking on any raster layer in the layer listand choosing Image Band Correlation from the popup menu.If you clicked on an RGB raster layer, the Image Band Cor-relation window is automatically populated using the 3 bandsin the layer. Otherwise you are prompted to choose 2 ormore grayscale (integer or floating-point) image bands (withmatching dimensions) for analysis.

OverviewThe Image Band Correlation window shows a 2D scatterplotof band values for each pair of spectral bands among thoseselected. The illustration below left shows the correlation

window with a single pair of image bands selected. Theoptional histogram for each input band is shown along theedges of the scatterplot. The correlation coefficient and bandstatistics are listed in the scrollable pane in the bottom partof the window along with the equation of the regression linethat is automatically computed for each pair of bands. If theimage in the View has the same extents and dimensions asthe bands you are analyzing, moving the mouse over theimage in the View highlights the 2D scatterplot positionscorresponding to a small target area around the cursor loca-tion. As described in the Technical Guide entitled SpatialDisplay: Highlight Image Cells from Correlation Plot, youcan also use the Highlight within Range tool to outline arectangular area of the scatterplot, highlight the correspond-ing cells in the View, and optionally save a binary mask raster

from the highlighted cells.

You can use the zoom controls to zoom the scatter-plot within its frame. The Reposition tool allows youto drag a zoomed scatterplot within its frame.

New

Save

Reposition Line

Highlight within Range

Preferences

Clear HighlightSelection

Tools and Preferences

Zoom Controls

Full

Maximum Detail Zoom In

Zoom Out

Listing ofcorrelationand bandstatistics andequation ofthe regressionline

2D correlationplot withchoice of colorpalette

Bandhistogram

MicroImages, Inc. • TNTgis - Advanced Software for Geospatial AnalysisVoice (402)477-9554 • FAX (402) 817-0151 • email info@microimages.com • web www.microimages.com • September 2014

The Line tool allows you to draw a two-point linewithin a scatterplot and see the equation of the linein the listing below the plot.

Band correlationplots for the sixpairings of siximage bands of aLandsat ThematicMapper image.

Band correlationplots for the threepairings of threeimage bands used inan RGB raster layer.

Highlight within Range Tool

The Highlight within Range tool allows you to draw a rectangle any-where within a scatterplot to set a range of cell values within each bandin that pair. Right-click after setting the rectangle to highlight cells withvalues within both of those ranges in the View window. This tool isdescribed and illustrated in detail in the Technical Guide entitled SpatialDisplay: Highlight Image Cells from Correlation Plot.

Saving ResultsThe Save icon button provides a dropdown menu that you can use to savevarious results of the image band correlation. You can save the correla-tion plot pane as a raster object, save a text file with the correlation statisticsand a listing of cell counts for each cell value pair, or save a text file withjust the correlation statistics. If you have used the Highlight with Rangetool to highlight image cells based on ranges in a correlation plot, youcan save the highlighted cells as a binary raster object.

PreferencesYou can use toggle entries on the Preferences iconbutton’s menu to show or hide the regression lineand histograms in the correlation plot. You can se-lect the form of the line equation to show in thewindow listing and choose a linear or logarithmicscale for the histograms. The Tracking Radius en-

try allows you to set the radius (in screen pixels) of the area around thecursor in the View pane that is used to highlight pixels in the correlationplot. The Colors entry allows you to change the colors used for the back-ground and other elements of the correlation plot. The Palette entry opensa dialog from which you can choose the color palette used to map thedensity ofp o i n t swithin thescatterplots.Use the Fontsentry to changethe font used for theplot labels.

Correlations fromMore than Two Bands

If you choose more than twobands to use for band correlation, theImage Band Correlation window auto-matically shows a scatterplot for each pairof the bands selected. These plots are arrangedbased on the order in which bands were selected,with the first selected band serving as the x-axis ofthe lower-right plot. Bands in between the first andlast one selected are used for the y-axis of plots withthe previous bands and the x-axis of plots with thelater bands (see the illustration of plots of 6 bandsimmediately to the right). If you open the Image BandCorrelation window for an RGB raster layer, it auto-matically shows plots for the three possible pairingsof the three input bands (far right).