Module 5:
Repeat Photography
Brief Background
Until recently, repeat photography was mainly used in ecology to assess habitat. More and more,
however, human geographers are utilizing this field method to assess human landscapes. Repeat
photography is basically finding an old image of the landscape you want to assess, and procuring a
contemporary image (presumably one you obtained through primary data acquisition) of the same
landscape. These two images are then compared and contrasted for temporal change. It is also
possible to assess landscapes over a series of time periods (e.g., every 10 years) to gain an accurate
assessment of landscape evolution!
Goals
This module is designed to:
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Give you experience “in the field”
Understand the practical application behind historical repeat photography
Recognize the significance of utilizing a “viewshed” to analyze a landscape
Materials
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Field Journal/Notebook
Camera (digital is best)
Historical photos (or postcard or other picture/image) of locations to be re-photo’d
For Viewshed: map(s) of area re-photographing, scale (ruler), pencil, eraser
Water/snacks/sunscreen
Deliverables
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TWO historical re-photographed landscapes, displayed in tables on a webpage
o Minimum of four photos (two historical, two contemporary) on webpage
 One landscape must be “human” dominated (e.g., capitol building, CBD, housing
developments, road improvements) and the other must be “physical” dominated
(e.g., agricultural land, river course, flash flood site, forest fire, etc.)
Brief analysis and interpretation of each landscape (½ page each)
One view shed of each contemporary image (two total)
Brief analysis of your view sheds, including the spatial phenomena you are able to assess with
your view shed, scale, and angle (½ page each)
Part I:
1. Select a historical photo (or postcard, or other picture/image)
a. Your historical image must have good resolution
b. The city of Tempe has many online so you can find an image of interest
(http://www.tempe.gov/museum/oslist.htm), but many have poor resolution.
c. Old historic images can also be found online by searching “images.google.com” for your
desired location (search for “historic postcard whatever city”)
2. Evaluate the historical image to determine the site from where it was taken
a. Critically inspect landmarks to determine position placement and angle of view
3. Find the site in “real life” and re-photograph it so you can compare the two images
a. Take several photos from different positions and angles for the best contemporary image
comparison
b. Black and white, digital, color, sepia, or a combination—the format is up to you
4. To help interpret your image, you should also create a “view shed”
A Sample Repeat Photo Example
Figure 1. Historical Photo: Puerto Peñasco, Mexico, cir. 1950.
Figure 2. Contemporary Photo: Puerto Peñasco, Mexico, April 2007.
From these two photos, it is clear that major changes occurred in the last ~50 years at “Rocky Point”.
For example, what was once exposed ocean floor at low tide has now been filled-in to make room for
industry. Curiously, the road has basically stayed the same, while the railroad tracks have been
removed! How can viewsheds (below, from Google Earth) lead to better understanding the landscape?
Part II: View Shed Analysis
In repeat photography, a view shed is basically the “field of view” of an image. Diagramming a view
shed in repeat photography allows for finely-detailed analysis of a landscape. The illustrations below
demonstrate different view shed angles and scales. There are many other combinations of angle and
scale, depending on the technology used. The view shed below take advantage of Google Earth’s
ability to “tilt” remotely sensed images. Each angle and scale offers a specific “view” allowing
assessment of different spatial phenomena.
For example, figure 5 gives a good “bird’s eye” view of the area outside the view shed, allowing a
researcher to analyze not only the immediate view shed, but adjacent regions as well. This type of
analysis can yield rich qualitative data about a landscape.
To construct a view shed, determine with precision the site from which your historic and contemporary
images were photographed. From that point, using both images and maps, fix the outer limits of the
images, and draw lines from the origin point to the outer edges of the views on each map copy. This
will create a triangular view shed that should roughly enclose the landscape and space of your images.
Appropriate maps are available online at http://maps.google.com or at any public library. You can also
use aerial photos and/or satellite imagery to help you construct the view shed. By now you have a solid
arsenal of imagery sites. Choose one that accurately portrays your photo.
Example of view shed comparison from composite satellite imagery (using Google Earth)
Figure 3. Contemporary Photo
Figure 4. View shed image, large scale, semi-oblique.
Figure 3. Contemporary Photo
Figure 5. View shed image, medium scale
Figure 3. Contemporary Photo
Figure 6. View shed image, small scale
The same effect can be achieved with a USGS topo map, a DOQ, or a DEM.
Use Paint or a similar program to draw-in viewshed angles. Alternatively, you can edit the picture in
PowerPoint, draw in the lines using the Draw features (View  Toolbars  Drawing), then “select all”
by holding down the “Ctrl” and “A” keys. “Copy” everything (“Ctrl” and “C” keys on a PC), open the
Paint program, and then “paste” it all by holding down the “Ctrl” and “V” keys. Then save the image as
a .jpg and put it on your webpage
Assemble the Webpage and Upload it
Save your work in the appropriate folders (gcu674 for your webpage and gcu674images for all of your
images). Publish “mod5.htm” and “mod5_files” to your gcu674 web space. Update the link on your
home page (index.htm), so the link to this module is correct; then upload your updated home page.