Module 4 Lab: Spatial Enhancement, Multispectral Data, and Band Indices

Spatial Enhancement and Multispectral Analysis

This week's lab assignment included several exercises to further familiarize ourselves with ERDAS Imagine and to switch between programs since both ERDAS and ArcGIS Pro are best used in conjunction. Our primary focus in the lab centered around the Olympic Mountains in Washington State.

The Process: A Detailed Look at Exercise 7

The culmination of our project was Exercise 7, where we synthesized the skills learned throughout our remote sensing course. We followed a meticulous four-step process to identify and map distinct environmental features:

  1. Histogram Analysis: We began by examining the histograms for each satellite data layer, looking for spikes that denote predominant pixel values. These spikes helped us pinpoint areas of interest by showing where features occur frequently and have consistent reflectance properties.

  2. Grayscale and Multispectral Viewing: Next, we analyzed the image in grayscale to identify contrast differences more clearly. We then switched to a multispectral view, adjusting band combinations to enhance the visibility of specific features, allowing us to see them in ways that grayscale could not reveal.

  3. Inquiry and Cursor Use: We used the Inquire Cursor tool to verify the exact pixel values of identified features, ensuring accuracy in our feature classification and mapping.

  4. Mapping and Visualization: Finally, we created detailed maps for each feature using the identified data points. These maps were enhanced by carefully selecting spectral bands that best displayed the distinct characteristics of each environmental feature.

Results of Exercise 7

Feature 1: Rivers

I could pinpoint the presence of water bodies by utilizing a spike in pixel values between 12 and 18 in Layer_4, identified through histogram analysis in metadata in ERDAS Imagine. These rivers appear dark, snaking entities against the brighter, vegetative backdrop. The chosen band combination for this display enhances the contrast, making the rivers stand out in dark blue hues against the green and purple terrain.

Feature 2: Snow

This feature was located through a combination of small and large spikes in pixel values across multiple layers, indicating snow's reflective properties. I used a false-color infrared setup, which beautifully contrasts the snow's white and blue hues against the dark reds of the mountainous terrain. This band combination not only highlights the snow but also accentuates the rugged topography of the mountains.

Feature 3: Variations in Water

The third image reveals subtle yet significant variations in the region's water quality. These variations, brighter than usual in the first three layers while consistent in the fifth and sixth, suggest differing sediment levels or water compositions. The true color representation was employed to closely mirror how these features would appear to the human eye, providing a natural perspective on the ecological dynamics at play.





 

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