How to Research Historical Aerial Photographs

Although this isn’t directly related to Google Earth, I thought there might be some people interested in researching old aerial photographs that aren’t available in Google Earth.  I’ve put together some instructions on how to do this research yourself.

We will be using the EarthExplorer website created by the USGS, which has  historical aerial photographs covering most of the continental US that often date back to the 1940s or 1950s.  These aerials are available to download at no charge.

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USGS Topographic Map Overlay

This overlay contains seamless topographic/land cover data for the entire Earth and a USGS Topographic Map overlay for the entire US, including Alaska and Hawaii.

Different map scales automatically load as you zoom in with the most detailed maps being available for the US.  Hill shading has been added to the maps giving them a 3D appearance.

USGS Topographic Maps

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Credits

ESRI ArcGIS Online Services

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Historic US State Boundaries

This set of files shows the configuration of United States and Territories every 10 years from 1790 to 1920. You can watch the United States start out with the 13 original States (actually I think it was 14 by 1790) and expand westward to the Pacific. I believe the only thing to change after 1920 was Alaska and Hawaii being changed from Territories to States, which is why I stopped at 1920.

The original shapefile data was obtained from the National Historical Geographic Information System. I simplified the polygons to allow them to display in Google Earth.

Each decade is an approximately 1 to 1.5 megabyte file that will take a minute or so to download and be processed by Google Earth, depending on the speed of your Internet connection and computer.

Historic United States Boundaries

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Credits

Google Earth Library

National Historical Geographic Information System

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Historical T-Sheets

Historical T-Sheets are shoreline maps that were created in the late 1800 to early 1900s for major waterways and coastal areas of the United States. The T-Sheets contain information such as locations of buildings, names of shoreline features, and detailed descriptions of shorelines.

This collection contains over 250 maps covering the following locations:

  • Puget Sound, Washington
  • Hawaiian Islands of Oahu, Maui and Kauai
  • Mississippi coast line
  • Everglades area, Florida
  • San Francisco Bay, California

These maps typically range in size between 1 and 5 megabytes. However, there are a few that are over 15 megabytes. These might take a few minutes to load, depending on the speed of your Internet connection. While they are loading, it will appear that nothing is happening. Just be patient and they will eventually load.

If you know of any other sources of online historical T-Sheets, please post a comment and I’ll add them to the collection.

Historic T-Sheets

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Credits

Google Earth Library

University of Hawaii

US Coast Survey of San Francisco Bay

USGS Open File Report 02-204

Mississippi Office of Geology

Puget Sound River History Project

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Impact Locations

The Impact Database shows the locations of confirmed and proposed impact sites throughout the Earth. Impact sites are locations where something from space (asteroids, comets, etc) has impacted the Earth.

Detailed information such as the size of the impact area, the age of the impact and geologic information is provided for the locations. Each location is color coded based on the Impact Classification, as follows:

  • Red – Confirmed
  • Orange – Most probable
  • Green – Probable
  • Yellow – Possible
  • Light Blue – Improbable
  • Dark Blue – Rejected

More information describing the various classes can be found a the author’s website.

Please post a comment if the link breaks. The authors of the file change the file name each time they release an update, which will break the link. You can also find the most current version of the KML file here.

Meteor Impact Locations

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Credits

Rajmon, D. and Roesler, W. (2009) Alz. in Rajmon, D. (2009) Impact database 2009.1

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Sea Floor Off San Diego, California

A detailed map showing over 600 square miles of ocean floor off the coast of San Diego California. The map was created by the USGS from multi-beam bathymetric data. Several major physiographic features and depth contour lines are shown. In addition, there are several placemarks which include a detailed view and description of various features.

Refer to Sea Floor Off San Diego, California and Multibeam Bathymetry and Selected Perspective Views Offshore San Diego, California for full citations and more information on how the USGS created these maps. High resolution PDF posters of the maps are also available to download from the USGS websites.

The original map provided by the USGS is a large PDF file. I extracted the portion of the map covering the ocean areas so the Google Earth land imagery is not covered. In addition, I extracted the various figures and made them available by clicking on a placemark in the location described by each figure.

I recommend switching Google Earth to Full Screen mode before using this unless you have a big wide screen monitor.

San Diego Sea Floor

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Credits

Google Earth Library

USGS

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Crime Scenes & Serial Killers

This data collection show the locations of notorious crime scenes, locations related to serial killers (where they lived, where they were captured, etc), and the locations of death row prisons throughout the United States. Each placemark contains a snippet of information about the location, including photographs of the scene or criminal. Some of the information dates back 200 years.

Quick word of caution. The content is a bit dark and may not be for everyone. But these are all very well publicized cases and are of historical significance to anyone interested in criminal studies.

Crime Scenes

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Credits

Sam034 at the Google Earth Community

Google Earth BBS Forum

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Google Earth Network Links Explained

Network Links are a very powerful, but very simple, feature of Google Earth that every Google Earth user should understand.  Also, EVERY Google Earth content developer that hosts KML/KMZ files online should understand Network Links and make use of them when it makes sense.  So take a couple minutes and read below to learn how to make use of this powerful feature of Google Earth.

Background:

Normally when you add custom KML content to you My Places, all of the data included with that custom KML file gets added to your main myplaces.kml file (saved under Documents and Settings\username\Application Data\Google\GoogleEarth\myplaces.kml).  For example, if you were to click on this KMZ file link and save the content to your permanent My Places folder in Google Earth, then you would have just made your myplaces.kml file about 15 megabytes larger than it was before and you would notice that it now takes Google Earth several more seconds to start up.  Do this 10 or 15 times and your myplaces.kml file can quickly grow out of control.  Also, if the original author of that KMZ file updates it, then you would need to  go back to their website and download it again to get the update.

If instead, you decide to use a Network Link, some important things will happen:

  1. Instead of your myplaces.kml file becoming 15 megabytes larger, it will only become 1-2 kilobytes larger.  You can add 1,000′s of Network Links without having to worry about the size of your myplaces.kml file.
  2. If you create a Network Link to a remotely hosted KML file, and the original author of that KML file decides to update it in the future (and doesn’t change the url/filename), then that update will automatically transfer to your machine.
  3. If you create a Network Link to a KML file stored on your local hard drive, then it won’t affect the size of your myplaces.kml file and won’t affect Google Earth’s load time.

How does all this happen?  Simple, because the Network Link does not load the actual KMZ file until you enable the Network Link in Google Earth by checking the box next to it.  The table below gives some recommendations on when to use Network Links, and what type of Network Link to use.

Continue reading Google Earth Network Links Explained

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