Archive

Posts Tagged ‘imagery’

Imagery: It is what it is: Well, not always.

May 12, 2019 2 comments

Being critical of all data, including geospatial data, is a chief theme of this blog and our book:  Use it wisely.  Know where it came from.  Know what has been done to it. Imagery has always been an important component of geospatial data, and today, it takes many forms, ranging from images taken on the ground with a phone or camera to those taken by webcams, UAVs, aircraft, satellites, and more.  Doesn’t this imagery “tell it like it is” and is it therefore exempt from us casting a critical eye on it?   I contend that no, images must be viewed critically so that you can determine if they are fit for your use in whatever project you are working on.

As one example in a larger story, consider the example of the removal of individuals from 20th Century photographs in the USSR. But lest we think such image doctoring was a thing of the past, there are dozens of articles that arise in current web searches highlighting modern day image manipulation, from fashion magazines to science journals, some inadvertent, some on purpose, some for purposes to benefit society and some unfortunately to mislead.  In the geospatial world, consider the image offsets on Google Maps in China that we wrote about not long ago.

Let’s discuss another aspect of image manipulation.  Consider the satellite images below.  They cover many different dates and are derived from many different sources.  But pay attention to what’s on–or off-the highways in the images.   These images all cover the same location—Interstate 30 – 35E interchange on the southwest side of downtown Dallas Texas USA, known locally as the Mixmaster.  Constructed between 1958 and 1962, you can spot, in some images, recent much-needed improvements due to the substantial increase in traffic volume in the past 60 years.

arcgis_online_dallas..PNGmapquest_dallas.png

Study area in ArcGIS Online (first image) and Mapquest (second image).

yahoo_maps_dallas.PNGbing_dallas.PNG

Study area in Yahoo maps (first image) and Bing maps (second image).

gmaps_web_dallas

Study area in Google Maps (it appears the same way in Google Earth). 

Notice anything missing on the Google Maps image?  No traffic. This would be unheard of, day or night, in this busy part of one of the largest cities in the USA.  Obviously, a vehicle-removal algorithm has been applied to the image. It is actually quite impressive, because the algorithm seems to only be applied to moving vehicles–cars, buses, trains–and not to stationary vehicles.  No doubt it is applied to make the process of viewing and interpreting the now-clearer imagery easier.  Interestingly, the moving-vehicle removal seems to only, at the present time, be present in running Google Maps on the web on a tablet or laptop:  Running the Google Maps app on a smartphone shows moving vehicles (below).

gmaps_dallas_app_on_phone.png

Study area in Google Maps app on smartphone. 

Key takeaway points and teachable moments here include:  (1) Images that can be obtained in web mapping services, in geodatabases, and portals should not be considered the same view that would be seen if someone were to be peering over the side of a UAV, airplane, spacecraft, or standing next to a webcam when the image was captured.  They can and are manipulated for a variety of purposes.   They need to be viewed critically.  At the same time, we can marvel and appreciate the many choices we have nowadays in imagery for use in geospatial analysis.   (2)  The machine learning and artificial intelligence techniques applied to imagery are further evidence for the enterprise nature of geotechnologies:  GIS is increasingly connected to mainstream IT trends and innovations.

–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

Hangar: A new on-demand UAV Data Service

October 28, 2018 Leave a comment

We have written about the rapid evolution of imagery platforms and portals many times in these blog essays over the years.  One major recent advancement is the UAV service from Hangar, an Esri business partner.  This service allows data users to order UAV imagery and receive it according to their project specifications:
https://www.spar3d.com/news/uav-uas/hangar-esri-reality-data-arcgis/

In my way of thinking, it is sort of like an” Uber for Drones”.  Let’s say you don’t have a pilot’s license, or time, or equipment, or expertise to fly your own UAV imagery.  Hangar is a new UAV service covering all areas that may be of interest to a client requiring imagery.  For this service, Esri partners with Hangar, a company that holds hundreds of waivers to fly almost anywhere and the expertise and equipment to serve clients from just about any discipline and with any need.   For more information, read the article “Hangar Joins Esri Startup Program to Add ‘Task & Receive’ Aerial Insights ArcGIS:”   https://www.prweb.com/releases/2018/05/prweb15514744.htm. 

And two of the best examples of some of the Hangar imagery is this story map of the devastation from the Carr fire in California and this story map showing some of their imagery for Kilauea, shown below.   Be sure to zoom and pan the 360-degree UAV imagery shown in these story maps.  Warning!  They are highly addictive and fascinating.  And for those of us in education, they make for an attention-getting teaching tools which I have already used numerous times from primary school to university and beyond to teach about wildfires and volcanic hazards.

uav_hangar.JPG

-Joseph Kerski

Categories: Public Domain Data Tags: , ,

Historical Imagery for the entire world now available via Wayback Service in ArcGIS from Esri

July 5, 2018 2 comments

I know that many of you regularly want to examine changes-over-space-and-time with imagery and GIS for research or instruction purposes.   As of last week, 81 different dates of historical imagery for the past 5 years now reside in ArcGIS via the World Imagery Wayback service.   For more information, see: https://www.esri.com/arcgis-blog/products/arcgis-living-atlas/imagery/wayback-81-flavors-of-world-imagery/

You can access this imagery in ArcGIS Online, ArcMap, and ArcGIS Pro.  A great place to start is the World Imagery Wayback app – just by using a web browser  – https://livingatlas.arcgis.com/wayback/    A fascinating and an incredible resource for examining land use and land cover change, changes in water levels of reservoirs, coastal erosion, deforestation, regrowth, urbanization, and much more.  This resource covers the entire globe.

However, in keeping with the theme of our book The GIS Guide to Public Domain Data and this blog of being critical of the data, caution is needed.  The dates represent the update of the Esri World Imagery service.  This service is fed by multiple sources, private and public, from local and global sources.  Thus, the date does not mean that every location that you examine on the image is current as of that date.  I verified this in several locations where my ground observations in my local area show construction as of June 2018, for example, but that construction does not appear on the image.  In addition, several other places I examined from wintertime in the Northern Hemisphere were clearly “leaf-on” and taken during the summer before, or even from the summer before that.  Therefore, as always, know what you are working with.  Despite these cautions, the imagery still represents an amazing and useful resource.

wayback1wayback2

Sample from this imagery set for 30 July 2014 (top) and four years later, 27 June 2018 (bottom) for an area outside Denver, Colorado USA. 

Access data and analytical tools online from EOS Data Analytics

A new platform from EOS Data Analytics (https://eos.com/platform/) allows data users not only to access data, but even perform online image processing in a web browser.  It is a set of mutually integrated cloud products for searching, analyzing, storing, and visualizing geospatial data.  This is a representation of what we have been discussing on this blog, namely, the increasing adoption of Software as a Service, and in addition, the combination of SaaS with data services and analytical services.  Thus, GIS professionals can search for, analyze, store, and visualize large amounts of geospatial data in one platform.  Doing all this in one system and also in a browser is, quite frankly, quite amazing.

With the EOS Platform, GIS users have access to an ecosystem of four mutually integrated EOS products, which together provide a powerful toolset for geospatial analysts. Image data is stored in cloud-based storage and is available for image processing or remote sensing analysis at any time; this can be a raw user file, an imagery obtained from their LandViewer data portal, or an output file from their online EOS Processing tools.  The EOS Platform is currently available for free during an open Beta.   The LandViewer tool has been freely available for some time and will continue to be.

eos1

There are at least two reasons why image processing is the platform’s major asset: the processing of large data amounts runs online and offers as many as 16 workflows with even more coming soon. On top of that, users can get the best cartographic features of EOS Vision for vector data visualization and soon to come, analysis.

eos2

A list of EOS Processing workflows that can be filtered by industry and input data type.

I found the LandViewer tool easy to use, with a wide variety of data sets to choose from, including Landsat, MODIS, NAIP, and others.

eos3.png

The LandViewer tool interface.

eos4

Choosing one’s own area of interest via the LandViewer interface.

Imaging Spectrometer data from NASA AVIRIS

June 11, 2018 1 comment

The NASA AVIRIS mission has generated imaging spectrometer data for many areas of the USA since the 1990s.  The AVIRIS download portal for data from 2006 onward is on a node at NASA, here.  The AVIRIS sensor collects data that can be used for characterization of the Earth’s surface and atmosphere from geometrically coherent spectroradiometric measurements. This data can be applied to studies in the fields of oceanography, environmental science, snow hydrology, geology, volcanology, soil and land management, atmospheric and aerosol studies, agriculture, and limnology.  Applications under development include the assessment and monitoring of environmental hazards such as toxic waste, oil spills, and land/air/water pollution. With proper calibration and correction for atmospheric effects, the measurements can be converted to ground reflectance data which can then be used for quantitative characterization of surface features. In short, AVIRIS can collect in over 200 bands and therefore it can help analysts work out details such as vegetation health, or even species type, from the data.

The AVIRIS portal, presented in a Google map with popups with download links, as well as the  metadata file (in plain text format, available here)  both look very dated.  But this is a case where we encourage the user to give it a try–the portal may not look modern, but the data behind the portal is incredibly useful.   One can toggle data layers in the right hand corner of map to show All AVIRIS data or the Attrib. Filtered data (data that meets the attribute criteria but ignores the spatial filter).  One can also bound a box on the map, which has long been a favorite feature of mine on data portals, using the red rectangle to activate.  To update the spatial filter, click the “Update Map” button below the map.   The files are not streamed, but must be downloaded; perhaps because of their large size (typically over 1 GB).  Again, think “old school” formats – zip files and TAR files, but again, the data are plentiful and useful.   A set of previews are available, for example, here, and shown below.  For more information about AVIRIS data, see this link and this link.

aviris

 

The AVIRIS data portal.

aviris2.JPG

A sample AVIRIS image. 

A Review of the Geoportal

March 19, 2018 1 comment

The GEOSS is a portal run by the European Space Agency (ESA) Group and the Group on Earth Observations (GEO) that provides one way to access earth observation data from around the world.   The site focuses on satellite imagery–Sentinel and Landsat data.  One helpful feature about the site is the ability to send search results to social media or via email.  A list of Popular Searches is a good place to start with the site.  The site is definitely worth investigating as it features a wealth of data.  I found myself wishing that there were more predefined searches listed there (currently 4).  The site also offers a login option and the ability to save your “workspace” which is an intriguing idea; using this feature, you could come back to the site and continue searching and downloading with the knowledge of what you have done previously.  There are different formats available, although at many points in my work with the site, I was confused as to how to proceed, or what format my file would be in, and if I was truly downloading the extent shown in the interface.

geoportal2

Interface for the Geoportal.

Like other portals, this one allows search terms, but without knowing what is there, the user is left with some confusion knowing what search terms to use.  I found myself really wanting a tutorial and a list of data sets I could browse through.  Searching is good but the users also need to know what the possibilities are.  I am intrigued by the data offerings on the site but had trouble navigating and discovering resources; I frequently encountered this message below and even had trouble drawing the bounding box for my desired search area.

geoportal1

Given the data holdings that are available via this portal, I think it is worth investigating further.  The about page on Geoportal lists enhancements to the site that are continually being made, and the mission of the page states that one goal is to make the site intuitive and easy to use.  I therefore have high hopes that it will be moving in this direction.  Give it a try!