Lab 1: Introduction to Software and Remote Sensing Applications

Introduction

In this lab we will become acquainted with the computer lab and/or Vlab interface, Google Drive folders and software. This lab will also explore some of the recent developments and applications in remote sensing. The lab will also go over the basic navigation and functions of the software ENVI.

Learning Outcomes

Learn about some of the many recent applications of remote sensing
Establish an understanding of the data storage and the benefits of using a standardized folder structure
Copying and extracting compressed files (ZIP files)
Exporting images from ENVI and inserting into documents
Use ENVI user interface to view files and explore the basic navigation tools

Part I: Remote Sensing News Articles Summary

Read/listen/watch the below remote sensing focused articles. Summarize and discuss the articles in a one to to two page write-up, a minimum of 500 words. Include the following items in your write-up:

Summarize and discuss each of the below articles
Discuss which article was most interetsting to you and why
What do these articles tell you about the future of remote sensing?

Articles to Read and Discuss:

Scientists take flight to map California’s vast snowpack and measure flooding threats (Los Angeles Time (PDF available on Google Drive))
We used AI and satellite imagery to map ocean activities that take place out of sight, including fishing, shipping and energy development (The Conversation)
How scientists lasered in on a 'monumental' Maya city — with actual lasers (NPR)
The ocean is full of tiny plastic particles – we found a way to track them with satellites (The Conversation)
The simple ways cities can adapt to heatwaves (BBC)

Part II: Accessing and Viewing Data in ENVI

You will begin by creating a folder structure or "workspace" that will keep your files organized and prevent any confusion as you work with multiple datasets in the future. It is important to have the files you are working stored with on a local drive (C: in our case). Many processes in ENVI and ArcGIS do not work well or at all when data is stored in the cloud (i.e. Google Drive G: Drive), network drive (Z: Drive) or on portable USB storage devices.

About the Data
The specific data used in the lab are two images of the Lake Tahoe region, one from September 2023 and a recent image from January 2024. Both images were acquired by the European Space Agency Sentinel-2 satellites.

Create a new folder on the desktop by following the below steps:
1. Right click the Desktop
2. Click on New → Folder
3. Name the folder “GSP216_Lab_01”. Your folder should be located C:\Users\abc123\Desktop (abc123 will be your Humboldt user name). If you are working on your personal computer you may choose to change the directory location but keep the general file structure the same.
In future labs you will want to back up your final work onto a USB drive, or cloud based storage like Google Drive or Dropbox. The hard drives (including the desktop) on the lab computers will be deleted every 24 hours. Be sure to always save and backup your work!
Open up your favorite web browser, log into myHumboldt and navigate to your Humboldt Google Drive. Click on "Shared with Me" on the left hand side. You should be able to see a folder for GSP 216 Remote Sensing, there is also a link to the shared Google Drive folder on the Canvas home page under resources. All of the lab data for this course can be found in the Lab Data folder. In the Lab Data folder locate the file “Lab1Data.zip”, Right Click on this file and select “Download”.
Move the ZIP file from your Downloads folder into your Lab 1 folder on your desktop. You can do this by dragging the file or by right clicking and copying and pasting the downloaded file into the folder.
Right click on the file “Lab1Data.zip” and select “Extract All”. Now the files have been uncompressed and are ready to view.
Go to Start Menu and "ENVI 5.7”. This will open the ENVI software package. Do not open ENVI Classic or ENVI Lidar, they are different programs.
Once ENVI has laucnhed open the first satellite image by navigating to File → Open and navigate to the desktop and locate the Lab_01 folder. Find and select the file “Tahoe09082023.dat” and click open. You may need to wait a minute for the image to fully load. The below image shows an overview of the ENVI interface.

You now should see the satellite image of Lake Tahoe in your ENVI viewer. This image was acquired by the Sentinel-2 satellite on September 8th 2023 and includes both California and Nevada. Use the navigation tools in the toolbar to explore the image. These tools include pan, fly, zoom. The Zoom to Full Extent Tool zooms out to show the entire extent of the image in the viewer. Watch the video below for an overview of the ENVI navigation tools.

You can use the Brightness controls to darken or brighten the display of the selected image. The valid range is 0 (dark) to 100 (bright). To return to the default value of 50, click the Reset Brightness button. Adjust the brightness of the image as necessary.

Image Window Views

In ENVI there are several tools that help you visualize the extent and geographic location of data. The Overview option shows a thumbnail of the raster and defines the extent currently shown in the view. Another useful tool is the Reference Map Link that opens up a new window with a variety of base maps that correspond to the geographic extent of the raster in the viewer.

First let's explore the Overview option. To show the Overview, click the Overview check box for the desired View in the Layer Manager window. The Overview appears in the top-left corner of each Image window view. The Overview Locater, a rectangle within the Overview, defines the extent to show in the view. As you move around the image the locator rectangle moves accordingly. Turn off the Overview by clicking the disable the check box.
Now let’s get an idea of the geographic area and terrain that this image covers. From the menu bar select View → Reference Map Link. This opens up a new window with a base map that shows the geographic extent of the raster in the viewer. Note: this feature is only available on Windows, not on Mac. Click the Switch Basemap drop-down list and select a different type of base map (satellite image, topographic, streets, etc.). After you’re done exploring, you can close the basemap window.
Now we will open a recent image of the same region acquired by Sentinel-2 on January 1st, 2024. Go to File → Open and select the file “Tahoe01012024.dat” in your Lab_01 folder and click open. You should now see a satellite image of the same area.
Explore the image by zooming in on difference areas to get an idea of what you can see in the image and how to navigate in ENVI. You can toggle between the two layers by checking/unchecking the boxs by the file names in the layer manager.
Now let's check out Blend, Flicker and Swipe tools that can be used to compare layers. These are found in the main toolbar . First click on the "Blend" icon in the toolbar . This creates an animation that blends or fades between the two selected layers. Click on the "Flicker" icon in the toolbar. This creates an animation that switches between the two layer. Finally click on the "Swipe" icon in the toolbar. This creates an animation that swipes between the two layer. Use these tools to compare the images.
Turn off the "Swipe" animation by clicking on the swipe icon again or right clicking on the "View Swipe" in the Layer Manager and selecting "Remove" or by clicking on the "X" in the upper right hand corner.
Click the "Zoom to full Extent". This button to zooms to the full extent of the data layer. You should now be able see the entire satellite image centered in your viewer. The next steps go over how to take export images for use in reports or presentation.

We will frequently be taking screenshots or exporting imagery in this course. Screenshots are an easy way to include images and figures into reports. Screenshots are also an easy to show someone what you're seeing on your computer screen instead of trying explaining it. Learn More About Taking Screenshots. There are many different options on how to take screenshots or export imagery in ENVI, the below video details some of the many options.

Make sure the recent image is visible (water levels will be higher), you can do this by unchecking the top image. We will now learn to use the "Chip to View" option in ENVI to save the current view as an image. This option is very similar to taking a screenshot. Go to File > Chip View To >File in ENVI. Select "JPEG" as the output file type and uncheck "Display Results." Save the jpeg in your Lab 1 folder. File names should not include spaces or special characters, I recommend including either the location or description as well as a date in the name. Check your lab folder to verify that the image has been saved.
Without moving the image or zooming in/out, uncheck the current image in the layer manager and check the other image to turn it on. You should now see the full extent of the image in your viewer. Repeat the above step and use the "Chip to View" to export an image showing the full extent image in September 2023. You will now have two exported images saved, both showing the full extent of the satellite image (one from Sept 2023 and one from Jan 2024).
Now we will repeat the steps but this time zoomed in on an area of interest. Use the zoom and navigation tools to focus in on an area of interest in the image (for example south Lake Tahoe, or Reno, NV). Once you are centered on your area of interest use the Chip to View to to export a jpg of the image.
Now export an image of the same area from the other time period. Without moving the image or zooming in/out, check the other image file in the layer manager, this will turn back on the other imagery. Use the Chip to View to to export a jpg of the same area of interest. You should have a total of four image, two showing the full extent and two zoomed in on a specific feature.
Open up a new blank document in Microsoft Word (or Google Doc, but you will need to save the file as a Word document or PDF for submission). Use the insert image/picture function in Word to insert your saved images. This will insert your exported image into your document. If necessary, screenshots or image exports should always be cropped appropriately and only include the necessary imagery.
You should have four images in your document: full extent of the two satellite images, and two zoomed in on the same area of interest.
Include a caption for each your figures (4). Note that captions should always be labeled with the figure number (i.e. Figure 1.) in bold followed by a description of the figure. An example would be: "Figure 1. Sentinel-2 satellite image of Lake Tahoe region acquired in September 2023". Captions for figures should be placed below images or figures. You also need to include your name, the date and class (GSP 216) on your document. Save the file in your Lab 1 folder.
You may close ENVI. You may complete Part I and II on seperate documents or combine the two parts into one document for submission.