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This blog combines articles from ADEC ESG Solutions, as well as FirstCarbon Solutions (FCS), an ADEC Innovation.

Aerial Photographs: A Tool Of Historic Research

Posted by Michael Dice on Oct 3, 2013 9:25:00 AM

In 1999, I began using historic aerial photographs to document historic-era cultural changes in my technical reports. At the time, online sources for such images were difficult to obtain. Therefore, I had to personally visit Whittier College (where the Fairchild aerial photo collection was kept), and the archives at San Bernardino County Flood Control every month or so. A researcher could go in, check index records, look at contact prints, order copies, and have them delivered in a few weeks. Southern California flood control districts have made use of aerial photographs for years: many of the earliest photos by pilots were taken at their request. The United States Agricultural Department and US Geological Survey were equally interested in the early aviators’ works. Fairchild and other pioneers made a good living out of these contracts. Many of these original photo collections date back to the mid-1920’s

In 2003, I wrote a technical cultural resource report that demonstrated the power of these images. A residential development project, now defunct, was set to be built in a small Southern California city. However, the proposed project wasn’t popular with local homeowners who didn’t want to see more houses built; one of the aspects of my study was the fact that an unusual geographic feature would have to be removed during development. The geographic feature was thought to be a “geoglyph” (a design scraped into or built upon the ground) created by prehistoric peoples.

Aerial photographs were used to demonstrate my opinion as to the importance of the geoglyph. In the photo above, we see a small mesa top that had been graded flat so that dryland cereal crops or hay could be planted and harvested. The graded area was accessed by dirt roads that originated at gates near farms in the valleys below.The photo on the right shows the anthropomorphic figure in question (north is at the top section of the photograph) with a whitish “star” in the “head”. 

I conducted a field visit of the site before obtaining these photos and noted that the ground had been repeatedly plowed. But because the field had lain fallow for decades, the plowing marks had mostly disappeared and native vegetation had returned. These photos are interesting because, given the fact that each picture was taken at a different time, one can see farm vehicles (at the tips of the red arrows) driving on the field and on the access road. The light colored “star” in the head” consists of rows of crops waiting to be gathered and baled by farm machinery. Magnification of other parts of these images showed that the farmer who cropped the field was likely located in a house to the southeast. Therefore, I discounted the idea that the geoglyph was an anthropomorphic figure worth preserving on the basis of these images.

In order to gain more insight into the matter, I have also included in this blog entry older photographs of the site, in order to provide a more solid, historical perspective into the matter. The 1938 images, enlarged below, were taken in a very stable plane with a big opening in the floor using a 10x10 inch box camera pointing down. As the plane flew overhead at about 5,000 feet above the landscape, a photo would be taken every minute or so. The pilot would fly a route using a compass, turn around once his transect was covered, and then fly a reverse path slightly offset from the first. By piecing various prints together, this allowed full coverage of many square miles of landscape. Engineers at the time would typically use the images to design flood control features, check and confirm drawn topographic maps, and develop soil type and agricultural condition maps.

Dozens of farms can be seen in these pictures taken in 1938. Crops grown include citrus, cereal and hay. Hay had been cut and was drying in the fields in this area, leaving short linear traces or dots on the field surface. The hay lying on these fields would have to be baled after a few days of drying to prevent mold and maximize quality. The citrus orchards (mostly oranges) were planted at different times and the bushy nature of the trees from orchard to orchard suggests different tree ages. Citrus species require certain types of irrigation and space between trees to produce the maximum bounty and quality for the farmer: the space and irrigation devices can be seen under magnification. These clues hint at how successful the farming community in the area was in 1938. Despite the Depression, Southern California citrus farms were quite successful because their products were being sold nationally and transportation of the finish crop was reliable. New orchards were being created every year despite the economic hardship.

In the end, I resolved that no geoglyph was in place onsite. Rather, the former residents and farmers in the area simply planted their crops in the best and most “fruitful” way: by designating certain trees and plants to areas where the soil, location, and conditions were best for them to yield the most produce.

Historic aerial photographs are more than curious museum pieces. They can lend insight into the past and provide interpretations for the present. Over the years, aerial photographs helped prove (or disprove) the existence of certain cultural resources, thereby also lending decades’ worth of help in helping ensure that certain developments and alteration to land areas do not harm any resources—natural or cultural.

Urban planners, city engineers, and property developers will do well to tap into the repository of available aerial photographs for the communities or land areas that they want to alter or modify with new buildings and structures, in order to make sure that they are developing the land sustainably—without destroying any resources, cultural or natural, so that they may still be available for future generations to utilize, examine, and simply enjoy.

The FCS staff is open to any and all explanations for these and other intriguing cultural phenomenon. Click below to request a consultation:

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