haze reduction

8/3/2019 Haze Reduction

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Software: ArcGIS - ArcView - ERDAS - ENVI - HTML

Simple corrections

ERDAS Example

1.) Begin by opening the file which you just finished georegistering (or use r:\lawers\data\landsat\bbc\my_resample.img).Display the 432 band combination.

2.) Select INTERPRETER > Radiometric Enhancement > Haze Reduction option from the main icon bar menu. Notealong the way all the other options. The HAZE REDUCTION dialog will appear.

This dialog offers you a chance to see the "model" that will preform a transformation on the data. Click on the VIEW buttonto start the ERDAS Model build. The DeHaze model will be loaded.

of 6SAL - Software - ERDAS - Simple Corrections

10/11/2011http://sal.ocean.washington.edu/tutorials/erdas/erdas1/correction.html



This model is very simple. It i llustrates the steps that ERDAS will take. The Input Raster is your image, the PSF Kernel is aconvolution filter. To understand how one pixel is convolved, imagine that the convolution kernel is overlaid on the data filevalues of the image (in one band), so that the pixel to be convolved is in the center of the window. The output value for theconvolution is, each value in the kernel is multiplied by the image pixel value that corresponds to it. The products aresummed, and the total is divided by the sum of the values in the kernel and assigned back to the center pixel. The kernelis then moved to the next pixel.

A High-Frequency kernel (high pass) has the effect of increasing spatial frequency. That is to say, when this kernel is usedon a set of pexels in which a relatively low value is surrounded by higher values the low value gets lower. When used withpixels in which a relatively high value is surrounded by lower values the high value becomes higher. In this way a simplespatial frequency of haze may be reduced.

3.) Now fill out the input and output fields of the Haze Reduction dialog. The software now knows that the data is LandsatTM data and will now pick a "DeHaze" model for Landsat. Click on VIEW to see it.





The grahic model illustrates the steps that ERDAS will go through. This "model" is specific to Landsat TM data and as youcan see it consist of picking between a matrix of weights for either landsat 4 or 5 data and the then determining themajority value with a kernel, put that data out to memory and the determining if any pixel has a value of zero beforemaking the output file. I wouldn't try to figure this one out. It is but one of the various approaches.

Fill out the dialog for input and output and click OK. Display your results side by side and look at the spatial profiles of thereflectence values

I also did a Point_Spread model (not using the model for Landsat Data). Look at the results.





It looks like more haze, but what are the DN values like?

You should do one or both of these models and save a result.

5.) To preform topographic correction; Display the Digital Elevation Model for the site

(r:/users/lawers/data/landsat/bbc/bbc_dem30.img) and then select INTERPRETER > Topographic Analysis > TopographicNormalization.





You will need the following information - SUN_ELEVATION=59.88; SUN_AZIMUTH=137.92. Remember to look at theVIEW of the model which is being preformed.

I'm glad someone else wrote this one for me. Click Okay and display your result.





Make some notes about what you see.

Spatial Analysis Laboratory - School of Oceanography - University of Washington


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