# ![](media/image1.jpeg){width="6.0in" height="2.4166666666666665in"}

# LAND COVER CHANGE PROBLEM:

**LESSON: Aerial Photography Interpretation**

# 

## **Purpose**

To develop an understanding of how to use an aerial photograph to
determine land cover type and to create a selective identification key
to aid in interpretation.

## **Overview**

In this unit, students will use aerial photographs to determine land-use
within satellite images. The \"bird\'s-eye\" view of the earth that
aerial photographs and satellite images offer is valuable. When we study
the Earth from above we can see things and how they relate to each other
in a way that can't be done any other way. An important difference
between the types of images is their spatial resolution or how much
detail can be seen. This difference is due to the altitude of the
aircraft or satellite. Aerial photographs have a very large scale and
high resolution (approximately 1 meter pixels.) This means that
individual houses and small roads can easily be seen, they generally
cover a smaller area than satellite images. Satellite images, in
contrast, cover a larger area, have a smaller scale and in most cases
lower resolution (in Landsats case the resolution a pixel is 30 meters)
so now we can see a larger area while still being able to identify
housing developments and large two lane roads are visible.(See Figure
API 1)

![](media/image2.wmf){width="4.913888888888889in"
height="1.742361111111111in"}

Figure API 1. An NAPP aerial photograph and Landsat color composite
(4,3,2) of a part of the city Upper Marlboro that compares spatial
resolution.

Aerial photographs are a more efficient and practical way to identify
parts of satellite images, especially in the classroom. This
identification process, sometimes called ground validation or ground
truth, is where information is collected at the same site and at the
same time that the satellite image was taken. The "ground validation"
interpretation of this units satellite image is completed by using the
aerial photographs. This lesson provides the foundation for how the
students will use the aerial photos to interpret the satellite images in
the change detection lesson.

Once students learn to "read" an aerial photograph they can derive great
deal of information about a study area. They can see where houses are in
relation to industrial areas. They can determine if a wooded area is an
orchard or a forest. They can even tell if the forest is evergreen or
deciduous. One way to teach students photo interpretation is to use
local aerial photographs. Students will learn to recognize familiar
landmarks from this "birds-eye" perspective and can transfer that
knowledge to aerial views of different regions. (See [Appendix
C](http://ltpwww.gsfc.nasa.gov/growsmart/appendix.html) to acquire data
that relates to the student's local school.) When they look at the
photos, they "drive" down the roads and pass landmarks in their minds as
they visually explore the photos. Quickly, they can spatially make sense
of their world in a meaningful manner that will make the satellite image
change detection very easy.

> **Advantages of Aerial Photography over Ground-Based Observation**

-   Aerial photography offers an improved vantage point (bird's eye
    view).

-   It provides a permanent recording on a larger scale.

-   It can have broader spectral sensitivity than the human eye.

> ([Aerial Photography and Remote
> Sensing](http://www.colorado.edu/geography/gcraft/notes/remote/remote_f.html),
> Shannon Crum, Department of Geography, University of Texas at Austin,
> 1995. visited 8-6-00)

## **Interpretation Features**

There are *eight* characteristics are used identifying features in an
aerial photograph, many of which can be used in satellite images. In
this lesson the students are asked to use all eight characteristics to
help in identifying of land cover objects.

The information in this section is adapted from the following web sites:
**([Volume 1: Air Photo Interpretation and
Photogrammetry](http://umbc7.umbc.edu/~tbenja1/santabar/vol1/lec2/2lecture.html),**
Lecture 2: Elements, Aids, Techniques and Methods of Photographic/Image
Interpretation **[2.3  Elements of Image
Interpretation](http://umbc7.umbc.edu/~tbenja1/santabar/vol1/lec2/2-3.html),**
Prof. John E. Estes, Remote Sensing Research Unit Department of
Geography University of California) and ([**Aerial Photography and
Remote
Sensing**](http://www.colorado.edu/geography/gcraft/notes/remote/remote_f.html),
Shannon Crum, Department of Geography, University of Texas at Austin,
1995. visited 8-6-00)

1.  **Tone** (also called Hue or Color) -- "Tone refers to the relative
    brightness or color of object on a photograph. It is, perhaps, the
    most basic of the interpretive elements because without tonal
    differences none of the other elements could be discerned."
    (Crum, 1995) (Estes, 1998)

> Examples of tone:  Example of color: 
>
> ![](media/image3.png){width="0.625in" height="0.625in"}
> ![](media/image4.png){width="0.6875in" height="0.625in"}
> ![](media/image5.png){width="0.53125in" height="0.625in"}
>
> To see details click on the images to open them in a web browser

2.  **Size** -- "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 Lake Minnetonka." (Crum, 1995)
    (Estes, 1998) If an object of a known size in the image, scale can
    be determined. Example: If a football field is 1 inch long in the
    aerial photograph and the distance from end-zone to end-zone is 100
    yards, then 1-inch = 100 yards.

3.  **Shape** -- "refers to the general outline of objects. Regular
    geometric shapes are usually indicators of human presence and use.
    Some objects can be identified almost solely on the basis of their
    shapes." (Crum, 1995) (Estes, 1998)

> The Pentagon Building
>
> (American) football fields
>
> Cloverleaf highway interchanges
>
> Examples of shape: 
>
> ![](media/image6.png){width="0.8333333333333334in"
> height="0.5520833333333334in"}
> ![](media/image7.png){width="0.4270833333333333in" height="0.625in"}

4.  **Texture** -- "The impression of \"smoothness\" or \"roughness\" of
    image features is caused by the frequency of change of tone in
    photographs. It is produced by a set of features too small to
    identify individually. Grass, cement, and water generally appear
    \"smooth\", while a forest canopy may appear \"rough\"."(Crum, 1995)
    (Estes, 1998)

> Examples of texture is easy to see in the larger image. Click on the
> image to see the larger image: 

[![](media/image8.png){width="0.8333333333333334in"
height="0.5416666666666666in"}](http://umbc7.umbc.edu/~tbenja1/santabar/vol1/lec2/2texture.html)

5.  **Pattern** *(spatial arrangement)* -- "The patterns formed by
    objects in a photo can be diagnostic. Consider the difference
    between (1) the random pattern formed by an unmanaged area of trees
    and (2) the evenly spaced rows formed by an orchard." (Crum, 1995)
    (Estes, 1998)

> Examples of pattern: 
>
> ![](media/image9.png){width="0.4166666666666667in" height="0.625in"}

6.  **Shadow** -- "Shadows aid interpreters in determining the height of
    objects in aerial photographs. However, they also obscure objects
    lying within them." (Crum, 1995) (Estes, 1998) Simply put, the
    longer the shadow with respect to other shadows in the photo the
    taller the object.

> Examples of shadow: 

[![](media/image10.png){width="0.8333333333333334in"
height="0.5520833333333334in"}](http://umbc7.umbc.edu/~tbenja1/santabar/vol1/lec2/2shadow.html)

7.  **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." (Crum, 1995) (Estes, 1998)

> Examples of site: 
>
> ![](media/image11.png){width="0.6979166666666666in" height="0.625in"}

8.  **Association** -- "Some objects are always found *in association
    with* other objects. The context of an object can provide insight
    into what it is. For instance, a nuclear power plant is not
    (generally) going to be found in the midst of single-family housing.
    But, a playing field with baseball diamonds will be in a residential
    neighborhood." (Crum, 1995) (Estes, 1998)

Residential Commercial Park Agricultural

![](media/image12.png) ![](media/image13.png) ![](media/image14.png)
![](media/image15.png)

Figure API 3. Figure API 4. Figure API 5. Figure API 6.

Student photo interpreters sometimes encounter difficulties when they
begin to use aerial photographs. In figure API 3-6, imagine how
difficult it would be for students identify some of these image
selections if they were not already identified. In this lesson, students
will first develop a key to the features they encounter in an aerial
photograph. They will use this key and their ability to interpret aerial
photographs to identify land cover types in their research area in the
final lesson.

## **Time**

-   2 class periods to understanding of how to use an aerial photograph
    and create a selective identification key

-   Time out of class can be used for completing the selective key.

## **Level**

Intermediate and Advanced

## **Key Concept**

> Communication skills
>
> Read and understand images produced by others
>
> Produce images for other to interpret
>
> Technology/Software Mastery
>
> Use computer software to scale images
>
> Use computer software to interpret image
>
> 12A Values and Attitudes
>
> Know why it is important in science to keep honest, clear and accurate
> records
>
> 12B Computation and Estimation
>
> Use, interpret, and compare numbers
>
> Estimate distances from maps and actual sizes of objects from scale
> drawings
>
> Decide what degree of precision is adequate
>
> 12E Critical-Response
>
> Be aware that there may be more than one good way to interpret a given
> set of findings
>
> Be skeptical of arguments based on very small samples of data, biased
> samples or samples for which there is no control sample

## **Skills** 

*Identifying* images

*Managing* time

*Integrating* information

*Analyzing* data

*Interpreting* data to make a decision

*Drawing* conclusions

*Using* computers

*Solve Problems* in a group setting

*Critically discuss* procedures

## Materials and Tools

-   2 printed NAPP Aerial photographs for each student group

```{=html}
<!-- -->
```
-   All the printouts for each of the NAPP Aerial photographs:

  ------------------------------------------------------------ ------------------------------------------------------------
  [Lanham](http://ltpwww.gsfc.nasa.gov/growsmart/data.html)    [Bowie](http://ltpwww.gsfc.nasa.gov/growsmart/data.html)

  [Upper                                                       [Bristol](http://ltpwww.gsfc.nasa.gov/growsmart/data.html)
  Marlboro](http://ltpwww.gsfc.nasa.gov/growsmart/data.html)   
  ------------------------------------------------------------ ------------------------------------------------------------

-   Selective Key worksheet

-   Color printer

-   3-inch square matte board

-   Rubber cement

-   Scissors

## **Preparation**

###### Prince George's Data

**Manual Selection Key Construction**

-   Download and print all the aerial photographs using the above
    materials and tools links.

-   Make enough copies (copies are best if each is printed individually)
    of each aerial photograph to hand out 2 of each photo for each
    student group.

-   Cut enough 3-inch square matte board cards for each student group to
    have one card. (extras never hurt)

###### Cut out the center 1-inch square from the 3-inch square matte board card. This will create the "Selection Key Window." 

###### Local Data (other than Prince George's Data) 

## Order the most recent NAPP Aerial photographs that cover the entire Landsat image area (remember that if you want to obtain your own Landsat image you want to refer to APPENDIX D: Landsat Resources For Educators) from the USGS from the web site [PhotoFinder](http://edcwww.cr.usgs.gov/Webglis/glisbin/finder_main.pl?dataset_name=NAPP)**.** Make sure that you do this with enough lead-time prior to the class time so that you can use this fantastic resource. You may want to purchase other aerial photographs from earlier dates to see the changes in your area during and/or prior to the satellite coverage (Landsat satellite coverage is from 1972 to the present.) The NAPP Aerial photographs are an invaluable resource for conducting remote sensing activities in the classroom.

-   If ordering local NAPP aerial photographs for use with this lesson,
    one of the best ways to make copies for the students to use is to go
    to a copier company and have them make copies of each photo that
    increases the size from 9-inch to 12-inch copies. Have the copies
    laminated. These will be very durable and an easily used classroom
    resources.

-   If you want to interpret the aerial photographs with the aid of a
    computer, then first scan the photos; 500-300 dpi is the recommended
    resolution, anything courser will not be useful. Once the images are
    scanned, then viewing the images can be a problem. To view the
    images, digital photo editors such as Photoshop or Photo Editor are
    preferred because the student can zoom in or out of the image If the
    scanned images are saved as JPEG format, both Netscape and Internet
    Explorer will open the images, but do not allow any manipulation of
    the images.

**Procedure**

-   Choose which student groups will work on which sections of the
    aerial photographs. This section does not need to be the same
    section that they will use when they interpret the ∆NDVI image in
    the final lesson.

-   Handout to each student or each group two copies of their aerial
    photograph area, a Selective Key worksheet, Interpretation Feature
    description sheet and their "Selection Key Window."

-   Review with the class the eight characteristics of image
    interpretation. The students can either go online to review the
    characteristics, you can develop a PowerPoint presentation or the
    quick lesson can be completed on the board.

-   Using the "Selection Key Window," have each student group select as
    many as 20 1-inch square areas on the aerial photograph that contain
    unique objects. (See figure API 7) Then the students place the
    "Selection Key Window" on one of the two photo copies and when they
    find an area they think is a good representation of that type of
    object (the Aerial Photograph Selective Key Worksheet describes how
    many and types of objects the students need to collect), carefully
    draw a square around the area using the 1-inch square.

-   Continue this process until they have at least 10 different object
    squares. Some of the squares can be of similar objects, different
    types of single family houses, but there needs to be some variety.
    **Try to find at a minimum 2 residential, 2 agricultural, 1
    commercial, and 2 transportation objects.**

Make sure that none of the selected squares overlap.
![](media/image16.jpeg){width="1.8729166666666666in"
height="2.515277777777778in"}

> Then have the students cut out each of their squares and paste them in
> the appropriate section of the worksheet. The students need to label
> on the worksheet each of their squares in the title area above each
> 1-inch photo square. The figure API 8 is a template of some of the
> features that they may select
>
> Figure API 7. Students searching for unique objects.
>
> When all the student groups have finished, have the students switch
> their worksheets and check the accuracy the other groups'
> interpretation. If both groups disagree with the identification, then
> they can check with the entire class.

Figure API 8. A template of a selective key similar to the one the
students will construct.

+-----------------------------------------------------------------------+
| # AERIAL PHOTOGRAPH SELECTIVE KEY                                     |
+-----------------------------------------------------------------------+
| +------------+------------+------------+------------+------------+    |
| | Image. 1 ∇ | Image. 2 ∇ | Image. 3 ∇ | Image. 4 ∇ | Image. 5 ∇ |    |
| +------------+------------+------------+------------+------------+    |
| | Farms      | R          | Industrial | Forest     | Amusement  |    |
| |            | esidential | Park       |            | Park       |    |
| |            | &          |            |            |            |    |
| |            |            |            |            |            |    |
| |            | Parks      |            |            |            |    |
| +------------+------------+------------+------------+------------+    |
+-----------------------------------------------------------------------+
| ![](media/image17.png) ![](media/image18.png) ![](media/image19.png)  |
| ![](media/image20.png) ![](media/image21.png)                         |
+-----------------------------------------------------------------------+
|   -                                                                   |
| ------------ ------------- ------------- -------------- ------------- |
|                                                                       |
|  Image. 6 ∇    Image. 7 ∇    Image. 8 ∇    Image. 9 ∇     Image. 10 ∇ |
|                                                                       |
|                                                                       |
|  Mall          Recreation    Race Track    Highway Clover Bridge over |
|                 Park                        Leaf           River      |
|                                             Intersection              |
|   -                                                                   |
| ------------ ------------- ------------- -------------- ------------- |
+-----------------------------------------------------------------------+
| ![](media/image22.png) ![](media/image23.png) ![](media/image24.png)  |
| ![](media/image25.png) ![](media/image26.png)                         |
+-----------------------------------------------------------------------+
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
|   Image. 11 ∇   Image. 12 ∇   Image. 13 ∇   Image. 14 ∇   Image. 15 ∇ |
|                                                                       |
|   Wetland       Gravel Pit &  Forested      Urban Railway Urban       |
|                 Landfill      Valley        Station       Reservoir   |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
+-----------------------------------------------------------------------+
| ![](media/image27.png) ![](media/image28.png) ![](media/image29.png)  |
| ![](media/image30.png) ![](media/image31.png)                         |
+-----------------------------------------------------------------------+
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
|   Image. 16 ∇   Image. 17 ∇   Image. 18 ∇   Image. 19 ∇   Image. 20 ∇ |
|                                                                       |
|   Large Urban   Urban         Urban School  Urban Bridges Mixed Urban |
|   Buildings     Residential                 over River    Buildings   |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
+-----------------------------------------------------------------------+
| ![](media/image32.png) ![](media/image33.png) ![](media/image34.png)  |
| ![](media/image35.png) ![](media/image36.png)                         |
|                                                                       |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
|                                                                       |
|                                                                       |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| # AERIAL PHOTOGRAPH SELECTIVE KEY WORKSHEET                           |
|                                                                       |
| ####### S                                                             |
| tudent Group Name \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ |
|                                                                       |
| #########                                                             |
+-----------------------------------------------------------------------+
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
|   Image. 1 ∇    Image. 2 ∇    Image. 3 ∇    Image. 4 ∇    Image. 5 ∇  |
|                                                                       |
|   Natural       Natural       Natural       Natural       Natural     |
|   Objects:      Objects:      Objects:      Objects:      Objects:    |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
|   Image. 6 ∇    Image. 7 ∇    Image. 8 ∇    Image. 9 ∇    Image. 10 ∇ |
|                                                                       |
|   Residential   Residential   Residential   Residential   Residential |
|   Objects:      Objects:      Objects:      Objects:      Objects:    |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
|   ---------                                                           |
| ------- ---------------- ---------------- ------------- ------------- |
|   Image.                                                              |
| 11 ∇      Image. 12 ∇      Image. 13 ∇      Image. 14 ∇   Image. 15 ∇ |
|                                                                       |
|   Transp                                                              |
| ortation   Transportation   Transportation   Commercial    Commercial |
|   ---------                                                           |
| ------- ---------------- ---------------- ------------- ------------- |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
|   Image. 16 ∇   Image. 17 ∇   Image. 18 ∇   Image. 19 ∇   Image. 20 ∇ |
|                                                                       |
|   Other         Other         Other         Other         Other       |
|                                                                       |
| ------------- ------------- ------------- ------------- ------------- |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+