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Archive for August, 2013

3D imagery and aerial photography: Public access versus public safety and security

August 26, 2013 Leave a comment

One of the recurring themes in The GIS Guide to Public Domain Data is that of open access: How and when spatial data is made publicly available. A recent report from BBC reporter Zoe Lleinman, highlighted the continuing problem of balancing the public interest in access to detailed mapping data for towns and cites versus concerns from government organisations with respect to security and public safety. Officials from Norway’s National Security Authority have refused permission for Apple to take aerial photographs of the capital city Oslo to create a 3D imagery layer that would include government buildings and restricted areas. Although the data Apple require can be sourced elsewhere (for example, from the Norwegian Mapping Authority), the authorities felt they would have no control over how data would be used if Apple were to acquire the data themselves. Other map companies have used 2D satellite imagery, which is not protected, for their mapping services.

Maintaining public safety, and national security, has long since ceased to be simply a matter of security barriers and guard dogs patrolling the perimeters of restricted areas; with increasingly easy to use web mapping services, access to detailed spatial information no longer requires a physical presence at the site. Terrorist events in Norway, and the targeting of government buildings, triggered a major debate about security and public access to such information. We discussed a similar problem with attempts to ban access to Google Earth data in India following the attacks in Mumbai in 2008. As the Norwegian and Indian authorities themselves acknowledge, there are many benefits to be gained from having access to detailed imagery, but developing effective data access policies, where information use is monitored, is an on-going challenge.

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CropScape: Agricultural Data Portal and Analysis

August 18, 2013 Leave a comment

As we explain in our book, The GIS Guide to Public Domain Data, agriculture data is available in an increasing number of formats and portals.  One of these portals and an extremely useful one is called CropScape.  CropScape hosts the Cropland Data Layer (CDL), a raster geo-referenced land cover data product created annually for the continental USA using moderate resolution satellite imagery but also extensive agricultural ground truthing.

Cropscape Agricultural Portal

The Cropscape Agricultural Portal.

CropScape allows the data user to browse crop data spatially and temporally from 1997 each year to the present.  Tools include the ability to swipe images of two different years in the map panel, the ability to access agricultural census data by county, and identify crops at individual pixels.  But probably most importantly, CropScape allows the data user to download crop data in a Geotiff format for any customized area of interest.  The data set is also available each year back to 2008 as a zip file for the entire USA.  This data set is over 1 GB in size.  Statistics range from grapes to pumpkins and much more, but the primary focus is on large area summer crops such as wheat and corn.  The spatial resolution is 30 meters.  The interface is fairly intuitive but if additional assistance is needed, an extensive FAQ exists.

As we discuss in our book, a great many well-intentioned data portals exist, but many are not designed with the data analyst in mind.   CropScape is definitely designed from the data and GIS analyst’s perspective, which is welcome given the importance of and need for agricultural data.

New data portals and open data initiatives

August 12, 2013 Leave a comment

The past few months have seen the launch of a number of new spatial data portals and open data initiatives as governments and organisations continue to liberate their data stores. The portals include the Open Geography Portal, providing access to the geographic information behind the national statistics published by the UK Office of National Statistics. The datasets have been made available for free under the terms and conditions of the Open Government Licence. Visitors to the site can search for a variety of statistics related spatial data sets including administrative boundaries, habitat, agriculture, postcode and INSPIRE compliant data themes in the extensive data catalog.

ONS Geography Portal

ONS Geography Portal

Although having open access to spatial data resources such as the ONS repository is beneficial, the current design of the ONS portal highlighted some of the same issues with map portals we identified in an earlier post, primarily the lack a focussed and intuitive front end to identify relevant data sets quickly.

As for open data initiatives, the European Commission has recently agreed to provide free access to data captured by its new Sentinel Earth satellites. After a protracted evaluation process, and following the example of the US Government’s Landsat program, the Commission concluded that the benefits of making the data available for free, with the anticipated growth in value-added services based on the data, outweighed any potential harm to private sector satellite operators (Source: SpaceNews). The first three Sentinel satellites are expected to be launched within the next year. Originally known as the GMES (Global Monitoring for Environment and Security) project, the new program of data capture has been renamed Copernicus.

Iowa Historical Imagery and other spatial data served in ArcGIS Online

August 4, 2013 Leave a comment

Some key spatial data from longstanding data portals are making their way onto platforms such as ArcGIS Online.  One of these is the data from the Iowa Geographic Map Server, served from the Iowa State University GIS facility.  The data set, searchable on ArcGIS Online via the keywords “Iowa Geographic“, is one of the finest examples of the holdings of a state data depository in an easy-to-use format.

Iowa State GIS Data in ArcGIS Online

Iowa State GIS Data in ArcGIS Online.

The data available includes aerial photographs from the 1930s, 1950s, and then every decade from the 1970s onwards.  Also included are an atlas from 1875, a general land office survey from the 1800s, a hillshade from Lidar data, the public land survey system, civil townships, and watershed boundaries.  Changes in agricultural practice, urban forms and size, river meanders, and much more can be explored via this map.  In addition, one can add the individual layers to one’s own map by pointing to the server URL found in the metadata for each layer.  That the metadata are well populated is another reason that the data portal has long been one of my favorites.  If one needs to download the data, those data sets are still available via the data portal at Iowa State University on http://ortho.gis.iastate.edu/.   While even more data are available via the data portal itself at Iowa State University, it is wonderful to be able to quickly browse a subset of the data via the ArcGIS Online map.  ArcGIS Online contains tools such as making layers transparent, adding map notes and bookmarks, and the ability to use the Iowa portal layers as a backdrop for one’s own data.  In addition, as a teaching and research tool, the way the data are served in ArcGIS Online allows land use changes to be quickly observed and measured without having to download each layer and loading them into desktop GIS software.

As data from portals such as the Iowa Geographic Map Server migrate to platforms such as ArcGIS Online, the data user will have additional ways to access that data.  It takes a commitment from data providers to serve their holdings onto these platforms, but data users in government, nonprofit, industry, and academia will all benefit.  Learn more about data portals, data platforms such as ArcGIS Online, and data types in our book The GIS Guide to Public Domain Data, and keep an eye on this blog.