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Need access to thousands of historical aerials and topographic maps at your fingertips? Try www.historicaerials.com

April 30, 2018 3 comments

Imagine having instant access to thousands upon thousands of historic aerial photographs and topographic maps to be able to examine change over time.  Thanks to a resource called Historic Aerials, you do have this wealth of information at your fingertips.  These aerials and maps, which go back 50, 60, and even 70 years or more, can be used for research, for instruction, for planning, and for other purposes.  Being in the field of geography and GIS education, I can think of many disciplines in which this can be used — urban and rural geography most certainly, but also biology, environmental science, city planning, history, agriculture, and also in GIS courses.  These resources foster spatial thinking about changes in time and space, from natural causes, such as volcanic eruptions or changes in river meanders, or from human causes, such as urbanization or the construction of reservoirs.  And given the connection that often exists between human and natural changes, sometimes these causes are intertwined–the construction of jetties along barrier islands often influences the naturally occurring longshore sediment transport and the migration of the islands themselves, as can be seen by comparing the historic to modern aerials of Ocean City, Maryland, for example.

The interface for the Historic Aerials is intuitive and provides tools that allow the user to compare USGS topographic maps of various years as well as the aerials themselves.  In the example below, I compare a 1958 with a 2009 aerial of a section of Grand Junction Colorado, before and after Interstate 70 and some surrounding housing was constructed.  You can also use the spotlight tool to “see back in time” for wherever you pan your cursor, and you can turn on the streets to see where  streets would one day be constructed on top of historical imagery.

The site comes from the Nationwide Environmental Title Research group, which has spent over 20 years collecting the worlds largest database of historical aerial images and topographical maps of the USA.  Their sources include USGS and USDA imagery, several private collections, and they are continually acquiring more. All the imagery they collect is orthorectified to provide the data in a searchable and precise geo-locatable format.  A print or digital image (for GIS users, GeoTIFF will be especially useful, delivered in lat-long coordinates, but JPG and PNG are also offered) of any of the maps or aerials is available.  In addition, a subscription service allows anyone to access the site with the following advantages: Full screen viewer, no advertising, PDF builder, quick JPEG downloads, and multiple user accounts.   I had a pleasant chat with the good people behind the site and found that their prices are quite reasonable.  Their FAQ, forum, and tutorials make it clear that they are committed to user success with these resources, and there are human beings behind this site to help as well.

Quite frankly, during my years working at the USGS, I always dreamed that my agency would create something like this.  Kudos to the HistoricAerials staff for making this a reality!

historic_aerials

The interface for HistoricAerials.com is quite intuitive and allows for fascinating investigations back in time for lands across the USA. 

Truth in maps

October 15, 2012 1 comment

There’s a saying that goes something along the lines of …’Whoever wins the war gets to write the history’.  Perhaps a similar saying could be applied to map making … ‘Whoever makes the map gets to interpret the location‘.

A map, paper or digital, is a representation of the Earth’s surface. That representation is an interpretation of the location, based on a particular perspective. Although a great deal of modern map making is automated, a certain amount of cartographic interpretation is still involved. Recent years have also seen a huge increase in the volume of citizen-generated mapping, freely available to anyone with an internet connection. Different mapping algorithms, cartographers, or citizen map makers may choose to emphasise certain features at the expense of others, introducing a degree of bias in the final product.

In a recent article for the BBC, Why modern maps put everyone at the centre of the world, Simon Garfield observes that “…  new maps are gridded by technicians and pixel masters, who may be more concerned with screen-loading speeds than the absence on a map of certain parts of, say, Manchester or Chicago.”

A map is a version of a location and like versions of history, some are more reliable than others. As end users, few of us can go check for ourselves, so we have to rely on the map producers to not only minimize the bias, but also document the manner in which the data was collected so we can decide for ourselves which version suits our requirements best.