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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.

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

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

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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).

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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

 

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.

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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. 

Planet’s Imagery Now Viewable by the Public

January 29, 2018 2 comments

Back in 2014, we wrote about inexpensive and the miniaturization of remote sensing, as exemplified in Planet Labs then-new small satellites.  A year later, we wrote about the company’s (now called “Planet”) Open Region initiative with the United Nation to share imagery under a Creative Commons license.  As described in this National Geographic post, Planet has now created a web mapping tool that allows users to examine two million images, updated monthly.  The tool, called Planet Explorer Beta, contains images dating back to 2016, at anywhere from 3 to 40 meters.  My favorite feature so far on the Explorer Beta is the ability to drag-and-drop two images to create a swipe map, to compare changes over time for any given area.  If you create an account and log in, you can explore daily, rather than just monthly, imagery.  Whether logged in or not, the tool is an excellent and amazing resource for teaching and research.  It could also serve as a great way to introduce students and faculty to imagery and encourage them to go further and deeper with remote sensing.

As most of the readers of this blog are work in the field of GIS, they will want to know how to use this imagery in a GIS.  The viewer described above is just that–a viewer.  You can only view the images online.  To actually access the data for use in your GIS or remote sensing work, begin with Planet’s Documentation.  As Planet is a professional satellite image company, it comes as no surprise that users have a multitude of options from which to choose–bands, date and time, cloud cover, sun elevation and azimuth, rectification, data format, and much more.  The imagery is available via a Planet Explorer interface and a Data API, which requires installing a Python client.

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Comparing imagery from two time periods in Colorado, USA, using Planet’s Planet Explorer Beta.

Possible Changes to NAIP Imagery Licensing Model

November 27, 2017 Leave a comment

As this blog and our book make clear, the world of geospatial data is in a continual state of change.  Much of this change has been toward more data in the public domain, but sometimes, the change may move in the opposite direction. The National Agriculture Imagery Program (NAIP) has been a source for aerial imagery in the USA since 2003 and has been in the public domain, available here.  But recently, the Farm Services Agency (FSA) has proposed to move the data model from the public domain to a licensing model.  The collection of this imagery has been under an innovative model wherein state governments and the federal government share the costs.

One reason for the proposed change is that the states have been $3.1 million short over the past several years, and FSA cannot continue “picking up the tab.”  Furthermore, delays in releasing funding from cost-share partners forces contract awards past “peak agriculture growth” season, which thwarts one key reason why the imagery is collected in the first place–to assess agricultural health and practices.  We have discussed this aspect of geospatial data frequently in this blog–that geospatial data comes at a cost.  Someone has to pay, and sometimes, those payment models need to be re-considered with changing funding and priorities.  In this case, agencies and data analysts that rely on NAIP imagery would suffer adverse consequences, but with the expansion of the types and means by which imagery can be acquired nowadays, perhaps these developments will enable those other sources to be explored more fully.  And, possibly, the model could be adjusted so that the data could be paid for and that all could benefit from it.

For more information, see the report by our colleagues at GIS Lounge, and the presentation housed on the FGDC site, here.

Two samples of NAIP imagery, for Texas, left, and North Dakota, right.

New LandViewer Tool for Quickly Finding and Analyzing Satellite Imagery

May 7, 2017 2 comments

The LandViewer tool and data portal quickly and painlessly allows you to browse and access satellite imagery for the planet.  The tool, developed by the Earth Observing System Inc.’s Max Polyakov, currently features Landsat 8 and Sentinel 2 imagery with more image sets soon to arrive.  Landsat 8 carries two instruments: The Operational Land Imager (OLI) sensor includes refined heritage bands, along with three new bands: a deep blue band for coastal/aerosol studies, a shortwave infrared band for cirrus detection, and a Quality Assessment band. The Thermal Infrared Sensor (TIRS) provides two thermal bands. Sentinel 2 is an Earth observation mission developed by the ESA as part of the Copernicus Programme to perform terrestrial observations in support of services such as forest monitoring, land cover changes detection, and natural disaster management.

Using the LandViewer tool, you can quickly zoom on an interactive web map to your area of interest.  You can filter on geography and time, including cloudiness, sun angle, and other parameters. At the time of this writing, 18 filters such as Atmospheric Removal, Panchromatic, NDVI, Thermal Infrared, False Color, and more, are available so that you can obtain the band combinations most suitable to your analysis in the areas of agriculture, geology, or other applications. A very helpful image interpretation screen is available to help you choose the combination that are best for your analysis goals.  You can do some contrast stretching in the web tool itself.  Then after signing in to the site, you can download the images in GeoTIF for further analysis using your favorite GIS tools.

The tool was also reviewed on the Geoawesomeness web site, and I wholeheartedly agree with their sentiments expressed–this is one of the most useful and fastest satellite image portals I have used. It is useful for research but also, given its ease of use, can even be used effectively to teach concepts of remote sensing.  Give it a try and let us know in the comments section what you think.

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Landsat scenes with band combinations possible for an area on the southwest side of Costa Rica.

 

Sentinel-2 Imagery Now Available

December 14, 2015 1 comment

Earlier this year we wrote about the launch of the European Space Agency’s (ESA) Sentinel-2A satellite and the mission to deliver a range of data products including land cover maps and bio-geophysical data. ESA have just released the Sentinel-2A orthorectified products, which are now available to download for free from the Sentinel-2 Data Hub https://scihub.copernicus.eu/s2/.

Sentinel-2a Data Hub

Sentinel-2a Data Hub

ESA have also posted a data quality report to document the current status of the data and provide information on product formats and features. As the programme is currently in a ramp-up phase, further improvements in the extent of coverage and the accuracy of the products are expected over the next few months.

Global Imagery Donation From Planet Labs

October 5, 2015 1 comment

Planet Labs, an US based imaging company that operates a constellation of miniature satellites, recently announced a new collaborative project with the United Nations and a number of private institutions and NGOs. The initiative, known as Open Region, will see the publication of $60 million worth of global imagery under a Creative Commons License Attribution-ShareAlike (CC-BY-SA) license.

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Planet Labs Color Images

The data will be available online through the Planet Labs imaging platform and accessed using web-based tools and/or an API for developers. The hope is easy and open access to the new data sets will provide a platform to help meet the UN’s Sustainable Development Goals, which include tackling climate change, promoting sustainable use of resources and eliminating poverty.

Daily Satellite Imagery for Planet Earth

December 1, 2014 1 comment

In this blog, we have written about the revolution occurring in the remote sensing world, centered on inexpensive and crowdsourced remote sensing. As described in this TED talk from Planet Labs’ Will Marshall, Planet Labs has launched small satellites of the dimensions 10 x 10 x 30 cm, weighing 4 kg, which can take images at 10 times higher resolution than conventional large satellites.  Early in 2014, the International Space Station launched 28 of these small satellites.  They plan to launch more than 100 that will image the Earth from a single orbital plane as the planet rotates beneath it.  Will refers to this system as a “line scanner for the planet.”

While our book and this blog discuss geotechnologies from a technical point of view, we also highlight the societal implications of these innovations.  Planet Labs’ work fits in well with these themes, because they are not only technically innovative, but their goal is to democratize remote sensing data.  They are asking:  “If you had access to imagery for the whole planet on a daily basis, what would you do with it?” Every point on the planet will be imaged every day with their platform.

And while the partnerships and avenues of dissemination data are still being worked out, this and similar efforts in the remote sensing world will surely impact data availability, crowdsourcing, copyright, privacy, decision-making, and other topics important to science, education, and society, in the months and years ahead.

 

Planet Labs:  Imagery and its democratization

Planet Labs: Imagery and its democratization.

 

 

Supporting humanitarian aid with open UAV imagery

February 10, 2014 3 comments

Last year we wrote about the imminent influx of high resolution imagery from unmanned aerial vehicles (UAVs) or drones and the great potential this could offer those agencies responding to emergency situations where the effective provision of humanitarian aid relies heavily on access to current, accurate and readily available map data.

When Typhoon Haiyan (Yolanda), reportedly the strongest typhoon to ever make landfall, struck the Philippines on the 8th of November 2013 it caused catastrophic destruction and loss of life. The Humanitarian OpenStreetMap Team (H.O.T) activated Project Haiyan to provide geographic base data for the affected areas.

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Providing updated imagery for the Philippines

However as Kate Chapman reported in a project update last month, although a large number of UAVs had been used to collect imagery immediately after the typhoon struck, much of the mapping activity was uncoordinated, resulting in fragmented data sources that were unavailable to the aid agencies. Although UAV imagery can provide much higher resolution data (5-10cm) than is currently available from satellite imagery sources (0.5m), if the data can’t be accessed when required, the relevant agencies don’t know what’s available and from whom or the licensing arrangements prohibit open access to the data, then the transient opportunities to put the data to good use are lost.

Given the increasing miniaturisation, reduced costs and availability of these devices, a register of publicly available UAV data sources, a crowdsourced OpenUAVImagery initiative or the “OpenReconstruction/Open Drone” platform described by the H.O.T.  would seem to be the next step towards making the most of this data resource.