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Wednesday, March 06, 2013

New Aerial Imagery vs. Google Earth and other Government GIS News

San Juan County, Washignton State, is looking to update its five year old aerial imagery and complete a LiDAR collection, but it needs partners to fund the $140,000 effort. As usual, the quesiton of why not just "use" Google Earth/Maps comes up. The unbylined article addresses it in a curious way. It states:

Google Earth, which is compiled from numerous sources is not an alternative to the county's own aerial photographs. The county's mapping data cannot be layered into Google Earth. Google Earth, which  is updated every few months depending where on earth one resides, uses several different companies each with their own systems. Here's an explanation of why agencies can't use it. 

The link to "an explanation" points to a piece from The University of Virginia which sources the Tibetan and Himalayan Library to explain why many users can't just use Google Earth. After explaining where Google gets its imagery comes the explanation.

Many people are familiar with Google Maps and Google Earth and may wonder why it is not simply sufficient to use them. Google Maps and Google Earth do not use the OpenGIS-standard WMS service API, but rather a proprietary API for interfacing with other data streams and projects. This means that specialized work is necessary to get Google resources to work with other GIS resources, rather than just implementing them directly as WMS as one might do for OpenGIS-based resources and services. Google also provides satellite imagery in a single Mercator projection called the “Google Projection”. (http://docs.codehaus.org/display/GEOTDOC/08+Google+Maps+Projection) This introduces distortions to a map that are very difficult to correct. This may not matter for a small place like Charlottesville, but can entail major problems for a large region like Asia. Google has to do this because otherwise they could never manage all the math of multiple projections.

- San Juan Islander

Davidson County [NC] officials decided Tuesday to take a sharper look at properties with a new aerial survey.

The Board of Commissioners voted unanimously to pay a contractor $55,000 for the aerial Kucera “oblique imagery” survey. 

“We think this could save enough money in manpower to pay for itself in two years,” said Tax Collector Joe Silver. “The image is so good we can measure the dimensions of a building and get construction measures.”

That's one of the first announcements I've seen for an oblique collection not by Pictometry. The company has been very quiet since its merger/acquisition.

- High Point Enterprise

Hawkins County, TN has decided only some entities need to pay for geospatial data. Others do not.

The Hawkins County Commission voted Monday to allow the property assessor to "waive or prorate the price" of GIS (Geographic Information System) data and maps. 
The change comes from the realization of Assessor Jeff Thacker that the city of Church Hill would have to pay $7000 maps of the city. He leareed thatthe Tennessee Forestry Service could have used detailed maps and photographs when fighting a wild fire last November, had they had easy (perhaps free) access.
 
The resolution to charge for data dates back to a 2008 resolution and was intended to offset the cost of implementing a new GIS system. By the way, there is no dicussion of the license under which the data is provided.
 
by Adena Schutzberg on 03/06 at 07:03 AM | Comments | Bookmark and Share

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