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What sort of changes has your neighborhood, the area around your school or university campus, or even your own backyard seen over the past few years? Outside our Esri office in Colorado, a large condominium complex has been under construction for a year. Its construction invites consideration of scale, change, and geography. In my neighborhood and in yours, GIS provides an excellent toolkit to examine changes and the reasons for them.

For centuries, communities changed very little, and indeed, some communities today undergo very little change. Yet in most communities, changes in infrastructure, total population, and the makeup of that population are commonplace. In my neighborhood, the hilltop site was chosen because of the excellent views its residents will have of the Colorado Front Range. These, incidentally, were formerly enjoyed by my colleagues on the north end of our building! Regionally, construction reflects population growth fuelled by the combination of high-tech industries, including GIS, and amenities such as nearby universities, the mountains, and the climate, making Colorado one of the fastest growing states over the past half century.

One way to do this is to examine imagery in ArcGIS Online and add three types of basemaps: Bing maps aerials, the ArcGIS Online imagery, and the USGS topographic maps layer. These sources were created on different dates and thus provide an easy and rich data source with which to examine changes in local communities. Revisit a changing area often and capture and save the updated images as I did here. Toggle the layers on and off and/or adjust the transparency so that you can compare and contrast them. Combine this to population change data that is easily added in ArcGIS Online.den_ro_time1-300x296.jpg
Our Esri office in Colorado in the south-central portion of this image is noticeable for its blue-ish roof. Note the open space to the north of our building.den_ro_time2-300x296.jpg
Construction has begun, but note that in addition, a large office building now appears to the north of the east-west street.den_ro_time3-300x188.jpg
Construction proceeds. What other changes do you detect? What time of day were these images taken? What time of year were these images taken? What clues help you answer these questions?

Go outside and take pictures and videos around your local community. Write and sketch what you see. Revisit the same sites during different weather events and in different seasons, or in the case of my Esri neighborhood in Colorado, as construction progresses. Link these photographs, videos, and text to points on your ArcGIS Online maps. What changes are occurring, and why? What will your community look like and be like in 5 years? In 20 years? What can you do to influence your community in a positive way?

I invite you to use ArcGIS Online beginning with these simple but powerful ways.

- Joseph Kerski, Esri Education Manager
Back in 1998, I and my colleagues were thrilled with the arrival of Terraserver. While maps and images for use in GIS on the web today are commonplace, back then it was revolutionary. Suddenly, thanks to an agreement between the USGS and Microsoft, the GIS community had access to USGS topographic maps and aerial photographs down to 1 meter spatial resolution for the entire USA. Two additional features made this service extra special. First, these images were georeferenced, meaning that they could be easily used within a GIS environment. Second, these images were online: No CD-ROMs or other physical media were required! After downloading the maps and aerials for our area of interest, we could read these maps and images into our ArcInfo or ArcView GIS software. True, the header files often needed to be edited first, but this resource gave us a huge leap forward because we had terabytes of data at our fingertips via, later becoming Even better was when some enterprising folks at Esri wrote programs to automatically stream these images to ArcGIS.terraserver_screenshot-300x211.jpg

Now, 14 years later, Terraserver was recently retired. As the National Atlas recently wrote, “We note its passing and salute all those who developed the service. Many people were involved in this groundbreaking effort. Still, there were three individuals who largely provided the vision and hard work that resulted in this remarkable service: Tom Barclay (Microsoft), Beth Duff (USGS, deceased), and Hedy Rossmeissl (USGS, retired). The National Atlas switched over to services provided by Esri so that Atlas users can continue to link from our maps to large-scale topo maps and aerial views. This takes us full circle. The National Atlas Map Maker was the first on-line, interactive mapper offered by the Federal government. It was partially developed under a joint research effort by the USGS and ESRI
in 1997.”

A plethora of base maps, topographic maps, satellite images, and aerial photographs are now available to the GIS user and the general public such as via ArcGIS Online. Times have changed but the need for good base data lives on. While I don’t long for those days of tinkering with header files, I salute the early pioneers who made it all happen, and look forward to the future. The evolution of GIS data, and discussion about data sources, quality, and related issues are detailed and blogged weekly about in the book that Jill Clark and I wrote, entitled The GIS Guide to Public Domain Data.

I and my colleagues frequently need old aerials for land use change studies, however, and therefore, I wish Terraserver had remained online. Why couldn’t it have done so? What are now the best sources for old aerial photographs?

- Joseph Kerski, Education Manager, Esri

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