Aerial Photo 1935:

Image Compiliation:
Knoxville-Knox County Metropolitan Planning Commission, 2002.

Aerial Photography Source:
Tennessee Valley Authority, General Engineering Division.
Brief Description:
Aerial photography of Knoxville from the Tennessee Valley Authority flown on March 29 1935.
Source Data Description:
Aero Service Corporation of Philadelphia, Pennsylvania originally captured this aerial photography on March 29, 1935 for the Tennessee Valley Authority, General Engineering Division.  This is most likely the photography that was used in the compilation of the original 1:24,000 scale USGS Quadrangle Maps produced by TVA's Map's and Survey Division in late 1930's.  Photography such as this covered much of the Tennessee River Valley.  The original photographic series for Knoxville was composed of thirty-seven photographs captured along four flight lines.  It contained approximately 60% frontlap (or overlap) and 10-50% sidelap.  Overlap between photographs enabled the TVA cartographers to view the terrain in three dimensions using stereoscopes and to create contour maps.
Geo-Positional Accuracy:
To be used within a modern Geographic Information System or GIS, the 9" by 7" contact prints were first scanned at a high resolution.  Next, each digital image was georeferenced.  This process correctly scales and rotates the photograph to its real world position by matching features seen on the 1935 aerial, such as a road intersection, with the same feature found on mapping and photography already spatially referenced within the GIS.
Currency:
The 1935 MrSid was created from TIFFS on:  April 2008.
Sub-Classes:
None.
Other Details:
The end goal was to produce a "seamless" composite image of the entire photographed area, but due to the high degree of overlap, any one feature could appear on as few as one and up to as many as eight photographs.  To resolve this, a 1500' by 1500' grid system was created and overlaid upon the photographed area.  Within each cell of the grid, a source photograph was choosen by: 1) selecting tiles from the same photograph within a contiguous area, such as a neighborhood and 2) selecting tiles closer to the center of the original photo center thereby minimizing radial displacement which occurs most prominently at the edges of an aerial photograph.  The final step in the process was to mosaic image tiles into a seamless photograph.  This was performed using an image compression software.
While the end product is "seamless" in the digital sense, the image that you see above is composed of as many ten separate photographs from the original series and does contain imperfections along the photo edges.  These cut lines are evidenced by a slight displacement along image tiles or abrupt changes in the contrast.
As a historical reference, the image is of great value, but GIS also offers the ability to view this image coincidentally with other features found in the GIS database.  For example, when viewed with current road network or building footprints, it enables a user to assess how an area has changed over the course of the last seventy years and to get a glimpse of the results of decisions and policies made in the preceding decades.  In some cases, the changes are few, but in others, the Knoxville of today is quite different from the one shown here.

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