Lab - INTRODUCTION TO IMAGE INTERPRETATION

This exercise is designed to introduce you to procedures used in image analysis. The image diagnostics (or clues) that we use to identify and classify features that we see depicted on images are as follows:

(S) Size (Sh) Shape (T) Tone or color (Tx) Texture (P) Pattern (St) Site or location (A) Association or context (Sd) Shadow (Te) Temporal characteristics

During this lab you will identify features on different digital aerial imagery. Use one or more of the diagnostics, logic, and inference to answer the questions posed for each location. You may not always be certain that your answer is correct, but make a best guess in every case. Briefly explain your reasoning if asked to do so.
Note: When asked to indicate diagnostics used in your feature identification, respond by using initials provided in parentheses above. When asked for the type of aerial imagery, respond with the appropriate initials indicated in parentheses as follows: (P) Black and white panchromatic aerial imagery (IR) Black and white infrared aerial imagery (C) Natural color aerial imagery (CIR) Color infrared aerial imagery

Outline:

Materials

Image Interpretation Image interpretation involves examining aerial photographs/images for the purpose of identifying objects and judging their significance. Novice photo interpreters often encounter difficulties when presented with their first aerial photograph. Aerial photographs are different from ‘regular’ photos in a variety of ways (perspective, scale, visible/infrared wavelengths). The following image diagnostics (or clues) can aid in identifying objects on aerial photographs.

Image Diagnostics Size – the use of size as a diagnostic characteristic both the relative and absolute sizes of objects can be important (cars vs. trucks or buses; single family vs. multi-family residences, brush vs. trees, etc.). The size of objects must be considered in the context of the scale of a photograph. The scale will help you determine if an object is a stock pond or Clinton Lake.

Shape – the shape of objects/features can provide diagnostic clues that aid identification. For example, roads can have right angle turns while railroads can not. Man-made features have straight edges that natural features tend not to. Regular geometric shapes are usually indicators of human presence and use. Some objects can be identified almost solely on the basis of their shape (for example, the Pentagon).

Tone/Color – tone refers to the relative brightness or color of elements on a photograph. It is, perhaps, the most basic of the diagnostic elements because without tonal differences none of the other elements could be discerned.

Texture – refers to the frequency of change or arrangement of tones. The impression of smoothness or roughness of image features is caused by the frequency of change of tone in photographs. The visual smoothness or roughness of an area can often be a valuable clue in image interpretation. Water bodies are typically fine textured, while grass is medium, and brush is rough, although there are always exceptions.

Pattern – refers to the spatial arrangement of objects. Pattern can be either man-made or natural. For example, consider the role of pattern as a diagnostic tool when distinguishing between an unmanaged area of trees (random pattern) and an orchard (evenly spaced rows).

Site – refers to topographic or geographic location. This characteristic of photographs is especially important in identifying vegetation types and landforms. For example, large circular depressions in the ground are readily identified as sinkholes in central Florida, where the bedrock consists of limestone. This identification would make little sense, however, if the site were underlain by granite.

Association – some objects are so commonly associated with one another that identification of one tends to indicate or confirm the existence of another. For example, smoke stacks, step buildings, cooling ponds, transformer yards, coal piles, railroad tracks = coal fired power plant.

Shadow - shadows aid interpreters in determining the height of objects in aerial photographs. However, they also obscure objects lying within them.

Temporal characteristics – refer to the date/time at which the photo was acquired. Seasonal variations in reflectance aid in interpretation.

Types of film Standard Films – record the visible wavelengths (red, green, and blue) Panchromatic film – normal black and white film Natural color film – normal color film Infrared Films – record visible and infrared wavelengths Black & white infrared film – black and white film that detect IR reflectance Color infrared film – color film that detects IR reflectance

Why IR? Color infrared photography, often called “false color photography”, is widely used for the interpretation of natural resources. Both standard-color and color-infrared films are manufactured to have three distinct layers, or emulsions. Each layer is sensitive to different wavelengths or energy.

Green, healthy vegetation has a high reflection level of near-infrared wavelengths and appears red on the processed film; red objects with very low near-infrared reflection appear green; green objects with very low near-infrared reflection appear blue; and blue objects with very low near-infrared reflection appear black. The primary use of color infrared photography is vegetation studies. This is because healthy green vegetation is a very strong reflector of infrared radiation and appears bright red on color infrared photographs. For example, leaves of healthy, growing vegetation reflect a high level of near-infrared wavelengths and appear red on color-infrared film. Unhealthy or dormant vegetation may appear light red or a light shade of blue-green, depending on the plant’s degree of good health. These color distinctions make color-infrared photographs useful in assessing the health of plants.

Water, on the other hand, absorbs near-infrared wavelengths and appears black in the image. Water with varying amounts of suspended particles appears as shades of blue. Shallow water would reflect the material present in its stream bottom. Bare soils appear as patches of white, blue, or green in most agricultural regions. Generally speaking, the moister the soil, the darker the soil color. Soil composition affects all color ranges shown on aerial photographs. Dry, sandy land will appear white in color. With the addition of moisture to this land, the white coloring turns into light gray or light tan. Soils composed of clay are darker in color than the sandy areas as well as tending toward more blue-green tones. Clay soils holding extreme moisture would resemble darker shades of the same colors. These identical soils, when high in organic matter, such as silt or loam, would be viewed darkest in the same corresponding color scheme.

IR Quick Reference Summary

IR Color Shift If feature reflects: Blue Green (except veg) Red NearIR

Then it appears: Black Blue Green Red

Vegetation Reflects more in nearer (see Spectral Reflectance Handout 2-35) Factors that influence IR response include: Different species (see Spectral Reflectance Handout 2-37) Temporal aspects (life cycle) Density of vegetation Health of vegetation (see Spectral Reflectance Handout 2-38)

Water Stands out clearly on IR photos Because water absorbs IR, it will appear black (see Spectral Reflectance Handout 2-35) Silt-laden water may appear blue-green based on sediment reflectance (see Spectral Reflectance Handout 2-35)

Soil Wet soil will absorb IR (because of water content) and appear dark Dry soil will reflect IR and appear lighter

Instructions for connecting to DASC Image Server Click on the Add Data button , and set the Look in: menu option to GIS Servers.

Double-click on Add ArcGIS Server.

Select Use GIS Services and click Next.

Enter http://imageserver.kansasgis.org/arcgis/services as the Server URL and click Finish.

This will create an ArcGIS Server connection called arcgis on imageserver.kansasgis.org. Double-click on the connection name to connect to the server. Once connected, you will see a list of folders containing map services available from the server. Click the Add Data icon . In Look in: menu option select GIS Servers and select arcgis on imageserver.kanasasgis.org. It may take a minute for it to respond. Click on Statewide folder and ask me what files to add for this lab.

Copy the G:\Fall-2015\G526\Lab04 from the server to local hard drive. Open Geog526_Lab4.mxd file in ArcGIS. This file contains a shapefile (Lab4_Features.shp) that outlines areas in multiple locations you will interpret. On the main menu, click on Bookmarks to see a list of locations you will use. There are multiple dates of aerial imagery for Kansas available at the Data Access and Support Center at the Kansas Geological Survey. You will access this data through their image server. If the imagery displays in ArcGIS upon opening the .mxd file, your computer has already been set up to access the image server. If you need to connect to the image server, follow the instructions in the guide.

ArcGIS Tips: Click on or off a layer to see the layers underneath. Use the zoom and pan tools to navigate the data. Use the Identify tool to view the attributes for a feature. Activate the tool by clicking on the icon in the toolbar. Then click on the feature (i.e. point, polygon) and a new window opens showing the attributes for that feature.

To view specific information about the imagery or layer, click on the file name in the Table of Contents, Right Click and select Properties. Under Source tab you will find information such as the number of bands, cell size (spatial resolution), pixel type and projection information.

–Location Kansas City, KS Click on the Bookmark labeled Kansas City, KS Make the following layers visible:
Lab4_Features ortho_1-1-1m_ks209_2008_2 2003_NAIP_2m_1

1.  What type of aerial imagery is this (hint: refers to the band combination? (1 point)  
   

Right click on ortho_1-1-1m_ks209_2008_2 in the Table of Contents and click on Open Attribute Table. This is the flight line information for the aerial imagery flown for Wyandotte County (FIPS Code 209), where Kansas City, KS is located.

2.  Use the attribute table for ortho_1-1-1m_ks209_2008_2 to provide the full date range for the aerial imagery flown for Wyandotte County: (1 point) 
   

3.  Identify the features indicated.  Indicate diagnostics used in your identification and briefly explain your reasoning. (12 points)
   

Location Identification Diagnostics Used Reasoning

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2

3

4

4.  Look closely.  What evidence do you see that indicates it might be possible to separate some species of trees? (1 point)
   

Location - Garden City and vicinity, KS Click on the Bookmark labeled Garden City, KS Make the following layers visible:
Lab4_Features ortho_1-1-1m_ks055_2008_2 2003_NAIP_2m_1

Provide the date range for the aerial imagery for this county (open the attribute table for ortho_1-1_1m_ks055_2008_2) (1 point)? ______________________

1.  If the average diameter of a circular center pivot irrigation system is one-half mile, what is the approximate scale of this photo? (2 points)
   

centerpivotscale.png

2.  You probably know that this is a relatively dry part of Kansas.  With that in mind, what do you think we have at location 5 (1 point)?
   
   
    How do you know (1 point)? 
   

3.  Identify feature 7. (1 point) ____________________________________________________
   

   Briefly explain your reasoning. (1 point)

4.  Identify feature 8. (1 point) ____________________________________________________
    Briefly explain your reasoning (1 points). Note that there are other similar features at other locations in the image.
   

5.  What features are located at 9, 10 and 11? (1 point) _________________________________________
   
    How are 9 and 10 different from 11 (What different use do they have)? (1 point)
   
   
   
   
    How do you know? (1 point)
   

   How are 9 and 10 different? (1 point) _________________________________________

   How do you know? (1 point)
   

6. What is located at 12? (1 point) ________________________________________

   How do you know that it is not an example of center pivot irrigation? (1 point)
   

Location - Topeka, KS Click on the Bookmark labeled Topeka, KS Make the following layers visible:
Lab4_Features 2003_NAIP_2m_1

1.  Identify feature 13. (1 point) ____________________________________________________________
   
    Explain your reasoning. (1 point)
   

2.  Identify feature 14. (1 point) ____________________________________________________________
   
    Explain your reasoning. (1 point)
   

3. Explain why pixel resolution is more important than representative fraction in the digital remote-sensing images. (2 points)

4. What are the white and black features in the image below? What image diagnostics did you use to identify these features? (2 points)

truecolorcloudshadow.png

All you have to turn into blackboard for this week is the final image you created above.