A lot of work and technology went into the production of the aerial maps. And it’s good to keep in mind that the maps weren’t produced for the average viewer, but rather for use by city planners. The “About” section of the website explains:
“A user may note that the color photography appears different from year to year, in terms of brightness, greens vs browns, etc. This is due to many factors, mostly the cooperation of Mother Nature and flight mission planning. Some years allow photos to be taken early (as in 2022, very early April) thus showing that tree budding and lawn greening had not yet begun. The prior (aerial photo) capture was executed in late April of 2018 and is much greener. The mission window for this type of photo capture is very narrow. Full leaf-in puts an end to the window as features such as manholes and other street features may be obscured.
“The purpose of these imagery flight captures is not for pretty pictures,” it continues, “we leave that to ‘consumer grade uses’ such as Google and Bing. The goal as city use is accurate ground feature capture and terrain mapping.”
How many photos are we talking about to create the aerial maps? It varies. And, according to Jim Ward, Lewiston’s GIS manager/coordinator with the Public Works Department, it depends on the scale of the flight. For example, for 1951 they had about 13 photos to make up the seamless mosaic. For 2018, there were over 2,000 individual photos.
There is also information on the website on who provided photography for each given year and how it was assembled. Each year shown is broken down below, beginning with the oldest collection:
1951: This photography was originally performed for the city of Auburn by James W. Sewall of Old Town. The photography area extended well into Lewiston’s “built-up” areas. The coverage of the 1951 project was limited to the westerly portion of the city.
1961: Originally a wall mosaic of aerial photographs done by Alster & Associates of Washington D.C. for the city of Lewiston, the large map was scanned, scaled, corrected and fitted into the model.
1971, 1975, 1994 (also applies to 1951): These aerial images were originally performed by James W. Sewall for the cities of Lewiston and Auburn. Aerial Photo and Survey of Norridgewock was contracted by the city of Lewiston to obtain the original film rolls, “assemble” them like a giant puzzle, digitize and correct them for optical distortion and make them into an accurate and seamless digital map overlay.
As a side note, all of these film collections were borrowed from the University of Maine’s Fogler Library Special Collections, where they now reside. For more information see https://archives.library.umaine.edu/repositories/2/resources/3368
1997, 2006: These years were again performed by James W. Sewall for the city of Lewiston. 1997, as a matter of fact, was also the first year a digital seamless aerial map was created of the city and was the basis for what became the city GIS.
2013, 2018: For 2013 and again in 2018, the city of Lewiston participated in a partnership between the city, Androscoggin County and the state of Maine GeoLibrary Ortho Imagery Program. The state program puts counties on a repeating five-year aerial update cycle. Woolpert, a multinational geospatial company, held the contract with the state for a number of those years.
2022: This imagery was obtained and provided by EagleView Technologies by way of a multi-year contract with the city to provide both oblique view imagery as well as traditional ortho (straight above) imagery.
Forthcoming for 2023: Imagery is being supplied to the city by EagleView Technologies by way of a multi-year contract with the city to provide both oblique view imagery as well as traditional ortho (straight above) imagery.
Gaps exist in the coverage years — there are no photo collections added between the years 1975 and 1994, for instance. That happened during periods when there was no funding available for the rather expensive aerial photography.
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