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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.

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. 

New Digital Globe Imagery in ArcGIS Online

January 2, 2013 1 comment

In chapter 3 of our book The GIS Guide to Public Domain Datawe discuss the increasing resolution, types, and ways to access sources of imagery and the  implications of these changes for data users.  Last week, imagery and for the continental United States and 60cm imagery for large parts of Western Europe arrived on the ArcGIS Online platform.

According to the announcement, http://blogs.esri.com/esri/arcgis/2012/12/20/digitalglobe-imagery-for-the-united-states-and-western-europe-added-to-the-world-imagery-map/, this is the first of several planned releases of new imagery from DigitalGlobe that will include Europe and many other parts of the world.

Another very useful feature is that with the Identify tool in ArcMap or the ArcGIS Online Content Viewer, or even inside the ArcGIS Online map viewer, the resolution, collection date, and source of the imagery can be obtained at the location on which you click.  The metadata applies only to the best available imagery at that location. You may need to zoom in to view the best available imagery.   The service was updated on the following servers: services.arcgisonline.com and server.arcgisonline.com.  If you have previously used the World Imagery map, you may need to clear your cache in order to see the updates.  For example, in the area in which I am examining in San Francisco, the popup indicates that the imagery is from 26 October 2010 and is at 30 cm resolution.

30 cm Digital Globe imagery in ArcGIS Online

30 cm Digital Globe imagery in ArcGIS Online

The Top 12 Most Useful Landsat Image Sites

August 4, 2019 4 comments

Recently, I wrote an essay about the sites that are, in my judgment, the top 10 in terms of containing useful geospatial data.   Now, I would like to describe what I consider to be the top sites for Landsat satellite imagery in terms of content and ease of use.  Let’s limit it to the Top 12.  Why might such a list be helpful?  First, there is no “one single site” to obtain Landsat data, and second, the sites are in continual flux, with some such as the Global Land Cover Facility disappearing and some having recently been created.  As with any consideration of data portals, make sure you have done a careful assessment of your data needs–band combinations, resolutions, formats, streamed services vs. downloaded files, dates, how many files you need, and so on, to guide you before you start searching.

(1)  The DevelopmentSeed’s Libra Portal.  I recently used this resource to include in the update (to ArcGIS Pro) for the Brazil land use change lesson that we host on the Spatial Reserves set of 10 hands-on exercises.  We wrote about the Libra portal here, and it remains in my judgment a no-nonsense resource that is easy to use with a wealth of options and data.

(2)  The EOS Data Analytics Landviewer, as we described here, is very useful and user friendly.   The EOS staff also wrote this helpful review of imagery sites.  Like the DevelopmentSeed portal, I find its user interface to be very straightforward.   The Landviewer includes Sentinel-2 and other imagery, as well.

(3)  Esri’s ArcGIS Living Atlas of the World has made amazing strides in content and usability since we first wrote about it here.  Most of Esri’s ArcGIS Living Atlas data is provided as streaming services instead of download, but for an increasing number of workflows, this is actually perfect.  The Living Atlas has in a few short years become probably the largest collection of spatial data on the planet, and so I recommend keeping it in mind not just for satellite imagery, but vector data as well, some of which can be downloaded, and all of it can be streamed.  Plus, you can contribute your organization’s data to the Living Atlas.  On a related note, be sure to check ArcGIS Online for imagery as well, the web GIS platform that Esri’s ArcGIS Living Atlas is based on.

(4)  The Esri Landsat Thematic Bands Web Mapping Application.   As we described in this post, through this application, you can access a variety of up-to-date and historical images in various band combinations, and save specific configurations and locations to share with others.

(5)  The USGS Earth Explorer.  While the Earth Explorer is in my view in need of improvement from the user’s perspective, it is functional and does contain a wealth of data, and sometimes is the best source for specific image sets.

(6)  The USGS Landsat Look Viewer.  I prefer the Landsat Look viewer’s interface over the Earth Explorer, as I described here.

(7)  The USGS GloVIS viewer.  I also prefer this interface over Earth Explorer.  GloVIS dates back to 2001 and was redesigned in 2017.

(8)  Landsat 8 archive on Amazon AWS.  As we described here, this has emerged as an amazing archive of data.  The user, as one might expect, is faced with a list of files rather than a fancy User Interface, but sometimes accessing specific files is exactly what one needs.

(9)  Landsat archive in Google Cloud.   Like the AWS experience, the UI is spartan but its data sets are vast, which is what one would expect from Google.

(10)  The FAO GeoNetwork.  This site focuses on vector data sets, but its raster holdings include many useful Landsat mosaics for specific geographic areas such as countries.

(11) Remote Pixel.  This is incredibly easy to use and blazing fast to zoom, pan, and query, and largely the work of a single individual.  It is my hope that if its developer does not maintain it in the future, that someone else will, because it is so marvelous.  Fortunately, the developer shows others how to host something like this themselves.

(12)  The Copernicus Open Data Access Hub, as its name implies, focuses on Sentinel data, but if you are interested in Landsat imagery, you probably are interested in other imagery as well.

satellite_image_portals_collageA few of the image portals described in this article.   We look forward to your feedback!

–Joseph Kerski

Verifying location data with blockchain cryptography

May 20, 2019 1 comment

Following on from Joseph’s recent post on some of the issues associated with the plethora of image resources we now have access to, another interesting aspect of verifying those data sources relates to the basic premise of proof. How can a data provider, whether that’s an individual or global company, prove the data they collect and publish are an authoritative and accurate representation of the locations they seek to record? The problems associated with Geolocation and GPS Spoofing are not new, with many protocols and procedures now in place to help prevent this type of deception. Conversely, GPS simulators are generally available, making it relatively easy for location hackers to interfere with GPS signals.

So how do data providers prove entities, in both the physical and human-made environments, really do exist at a particular location? One company, XYO, has been working on an alternative to satellite networks as a source of verified location information – the XYO Network. By augmenting our increasingly interconnected network of digital devices with location tracking technologies that incorporate blockchain cryptography, these co-opted devices (acting as sentinels or bridges) can be configured to recognise, validate and confirm the location of each other. As each device acts as a witness to the location of other devices; the more witnesses there are confirming a device’s location, the less chance there is that location is incorrect. The end result is a decentralised location data network that is arguably at less risk of being compromised.

Bound witnesses (sentinel and bridge devices) in San Francisco – https://matrix.xyo.network/map

Using device networks in this manner is an interesting new development in evolution of geospatial data and an emerging technology to watch.

 

A Report Card on the U.S. National Spatial Data Infrastructure (NSDI)

The Coalition of Geospatial Organizations (COGO) recently released its 2018 Report Card on the U.S. National Spatial Data Infrastructure (NSDI). The report card utilizes a letter grading system to depict the status and condition of the USA’s geospatial infrastructure.  COGO commissioned 24 content area experts to develop this second Report Card for the NSDI. These experts, drawn from the 12 member organizations of COGO, focused on the NSDI Framework to grade national efforts, and also candidly point to some of the shortcomings of those efforts.

The national assessment of the NSDI’s ability to meet future geospatial data, based on address, cadastral, elevation, geodetic control, government units, hydrography, orthoimagery, and transportation themes rose from a C in the 2015 Report Card, to a B- in the 2018 Report Card.   Grades improved across all themes; cadastral and transportation scoring a C- and a C, respectively.

The report also contains updated statements about the Federal Geographic Data Committee and the NSDI, which should be useful for anyone immersed in using geospatial data as well as to anyone teaching these concepts.  For example, on page 11 is a concise statement about what the NSDI should be, namely:
• A geographic resource for both the present and the future.
• A foundation for helping the public and private sectors use geospatial data for better decision making.
• A resource for many people and organizations working together towards common
goals.
• A collection of current and accurate geospatial data available for local, state,
national, and global use.
• An infrastructure for geospatial applications and services.
• A flexible resource that changes as technology, business requirements, and user needs change.

This 100-page document provides some excellent information about the history of data development and about the major data sets available for each theme.  In that sense, outside of the recommendations, the document is helpful as a short of “Data 101” document.  Plus, in some ways similar to the reviews that we have done on this blog, the authors review the major ways to access geospatial data.  The document provides insightful recommendations on how access can be improved, and how the data sets themselves can be improved, and so in the interests of all of us in the GIS profession, it is my fervent hope that these recommendations will be read and acted upon by those in the organizations responsible for each data set.

reportcard

Report card on the NSDI–a detailed and helpful document.

–Joseph Kerski

Categories: Public Domain Data Tags: , ,

Track on Track, Revisited: Spatial Accuracy of Field Data

February 4, 2019 3 comments

Back in 2014, I tested the accuracy of smartphone positional accuracy in a small tight area by walking around a track.  During a recent visit to teach GIS workshops at Carnegie Mellon University, I decided to re-test, again on a running track.  My hypothesis was that triangulation off of wi-fi hotspots, cell phone towers, and the improved GPS constellation would have improved the spatial accuracy of my resulting track over those intervening years.

After an hour of walking, and collecting the track on my smartphone with a fitness app (Runkeeper), I uploaded my track as a GPX file and created a web map showing it in ArcGIS Online.  Open this map > use bookmarks > navigate to the Atlanta and Pittsburgh (Carnegie Mellon University) locations (also shown on the graphic below on the left and right, respectively).   Once I mapped my data, my hypothesis was confirmed:  I kept to the same lane on the running track, and the width of the resulting lines averaged about 5 meters, as opposed to 15 meters on the track from four years ago.  True, the 2014 track variability was no doubt in part because I was surrounded by tall buildings on three sides (as you can see in my video that I recorded at the same time) , while the building heights on the Carnegie Mellon campus were much lower.  However, you can measure for yourself on the ArcGIS Online map linked above and see the improvement over those two tracks taken just 4 years apart.

I did another test while at Carnegie Mellon University–during my last lap on the track, I moved to the inside lane.   This was 5 meters inside the next-to-outer lane where I completed my other laps.  I wanted to see whether this shift would be visible on the resulting map.  It is!  The lane is clearly visible on the map and on the right side of the graphic below, which I labeled as “inside lane.”

To explore further, on the map above, go to > Contents, to the left of the map, and turn on the World Imagery Clarity layer.   Then use the Measure tool to determine how close the track is to the satellite imagery (which isn’t perfect either, but see teachable moments link below).  You will find that at times the track was 0.5 meters from the image underneath Lane 1, and at other times 3.5 meters away.

Both tracks featured “zingers” – lines stretching away from the actual walking tracks, resulting from points dropped as I exited the nearby buildings and walked outside, as my location based service first got its bearing.  But again, an improvement was seen:  The initial point was 114 meters off in 2014, but in 2018, only 21.5 meters.  In both cases, as I remained outside, the points became more accurate.  When you collect data, the more time you spend on the point you are collecting, typically the more spatially accurate that point is.

tracks_comparison

Comparison of tracks taken with the same application (RunKeeper) on a smartphone four years apart illustrate the improvements in positional accuracy over that time. 

To dig deeper into issues of GPS track accuracy and precision, see my related essay on errors and teachable moments in collecting data, and on comparing the accuracy of GPS receivers and smartphones and mapping field collected data in ArcGIS Online here.

Location based services on the smartphone still do not yet deliver the spatial accuracy for laying fiber optic cable or determining differences in closely-spaced headstones in cemeteries (unless a device such as Bad Elf or a survey-grade GPS is used).  Articles are appearing that predict spatial accuracy improvements in smartphones.  Even today, though, I was quite pleased with my track’s spatial accuracy, particularly in 2018.  I was even more pleased considering that I had the phone in my pocket most of the time I was walking.  I did this in part because it was cold, and cold temperatures tend to rapidly deplete my cell phone’s battery (which is unfortunate, and the subject of other posts, many of which sport numerous adds, so they are not listed here).   Happy field data collection and mapping!

–Joseph Kerski

Global Land Cover Facility goes offline

January 7, 2019 2 comments

The world of geospatial data portals is dynamic; new sites appear and others disappear.  Sites are shut down due to the end of a funding period, changes in technologies, or as a result of mission or personnel changes. One of the earliest and most useful sites particularly for remotely sensed imagery recently went off-line–the Global Land Cover Facility from the University of Maryland.  Their notice said, “The GLCF has had a very good run since 1997! Originally it was funded under NASA’s Earth Science Information Partnership (under the inspired leadership of Martha Maiden of NASA). Subsequently it was maintained to support our NASA-funded research activities especially those concerned with Landsat data.   We feel we have attained what we wanted to accomplish, and now it’s time for us to move on and explorer other ventures. The data and services provided by GLCF are now mostly available via government agencies, especially USGS and NASA.”

To expand on the last note above, what should you, the GIS user who loves imagery, do?  For the time being, the GLCF data are still on a no-graphics FTP site, here:  ftp://ftp.glcf.umd.edu/.   But better yet, we have examined numerous functioning imagery portals on this blog; start here.  These include, for example, LandViewer, EOS Data Analytics, NASA AVIRIS, the GeoPortal, Lidar from USGS, DevelopmentSeed, Sentinel-2, and many others.

glcf

Thank you, GLCF!  You provided a wonderful service, and will be missed. 

–Joseph Kerski

Quality Matters…

December 17, 2018 Leave a comment

When Apple Maps was launched six years ago it was not a resounding success, by any measure. Although much of the criticism levelled at Apple focussed on the application interface and the lack of some keys features Google Maps users took for granted, for many the main issue was the quality of the map data. Apple Maps was originally delivered on a platform of third party map data, including TomTom and OpenStreetMap, with the majority of the satellite imagery sourced from DigitalGlobe. In response to the criticism, Apple vowed to do better and set off on a mission to improve the application and challenge the dominance of Google Maps.

Many application upgrades later, the map data is still not considered to be of the same quality as Google Maps. For example, zoom into a location in Queens, New York and compare the quality and range of information reported for local transport services in Google Maps compared to the same site and services reported in Apple Maps. Both Apple and Google Maps provide the number of the bus service using a particular stop but Google Maps provides more … street view data to visualise (and confirm) the location of the bus stop and better integration of supplementary traffic and transport service information. 

Queens, New York – Google Maps

The same bus stop in Apple Maps is shown at a slightly different location (further to the east along 48th Ave) and lacks the integrated street view. 

Queens, New York – Apple Maps

All that is set to change with an ambitious plan from Apple to rebuild their map data platform (see reports in TechCrunch and Medium). Taking a leaf out of the Google handbook on data collection, Apple have invested in specially equipped vans and drones, decked out with GPS, LiDAR, high resolution cameras and other data capture tools. In addition, Apple is also generating map information from anonymised iOS device data, adopting a strict ‘privacy-by-design’ methodology, to improve road network and pedestrian traffic information. 

The new in-house Apple Maps service has been available on a limited basis in California, USA for a few months now and there are plans to roll the service out to the whole USA over the next year. No word yet on when it will be available further afield.