This past week Google introduced the latest iteration of their popular earth visualization program – Google Earth Version 5.0
In it was something I had been hoping for for months: a way to display historical aerial imagery and thus land use change around a climate monitoring station in an interactive timeline.
The best part: it is easy, and it is free.
for example, here is my first effort, a simple two frame blink comparator showing changes around the USHCN station MMTS sensor at the water treatment plant in Aurora, IL, a suburb of Chicago:
The yellow dot is the location of the USHCN MMTS thermometer, and the white arrows arrows in the more recent view point to some things that have changed around the sensor over a six year period from 1999 to 2005. You can view the individual larger images also: Aurora in 1999 and Aurora in 2005
Here is a ground level view of the MMTS at the water plant, looking north:
I spotted three things:
- Two large storage tanks were added due west of the sensor
- A new addition was put on to the north end of the building nearest the sensor
- A roof on a building to the NW across the road was changed
There may be more. Now with the help of the KML put together by surfacestations.org volunteers Gary Boden and Barry Wise, we can not only pinpoint the locations of the USHCN stations, we can watch what has changed around them from localized scales of a few hundred feet to citywide scales depicting urban growth. From Google Earth’s feature page, here is how it works:
Viewing Historical Imagery
By default, Google Earth displays most up-to-date imagery available. You can view historical imagery so that you can see how places have changed over time.
San Francisco in 1946
To access historical imagery, do one of the following:
- Click View > Historical Imagery
- Click the Clock icon in the toolbar above the 3D viewer.
Features of the time slider include:
- Click this to play an animation of a sequence. This works best if you move the range marker to define a time range smaller than the whole set. Click the adjacent buttons to step forward or back.
- Drag the range marker to the right or left to re-define the time range of data displayed.
- Click this to set options for the time slider.
- Zoom in or out to shorten or lengthen the date range covered by your timeline. This allows you to more easily see the different imagery that’s available within a shorter or longer period of time. Notice that, as you zoom in or out, the Start and End dates on the timeline change.
- Drag this to move the time range earlier or later.
The small vertical lines on the timeline indicate the dates of different imagery available for your location. Notice that the slider is automatically positioned at the far right of the timeline, showing that you are viewing more recent satellite imagery. Move back or forward in time by doing the following:
- Click the Forward or Back buttons above the slider.
- Drag the slider along the timeline. Note that regardless of where you release your mouse on the timeline, the slider automatically moves to the closest date for which imagery is available.
To try out his new feature with USHCN stations you’ll need two things:
Google Earth 5.0 which you can download here: http://earth.google.com/
I welcome any submissions of interesting discoveries by WUWT readers.