A theme running throughout our book The GIS Guide to Public Domain Data is to be critical of the data that you are using–even data that you are creating. Thanks to mobile technologies and the evolution of GIS to a Software as a Service (SaaS) model, anyone can create spatial data, even from a smartphone, and upload it into the GIS cloud for anyone to use. This has led to incredibly useful collaborations such as Open Street Map, but this ease of data creation means that caution must be employed more than ever before, as I explain in this video.
For example, analyze a map that I created using Motion X GPS on an iPhone and mapped using ArcGIS Online. It is shown below, or you can interact with the original map if you prefer. To do so, access www.arcgis.com/home (ArcGIS Online) and search for the map entitled “Kendrick Reservoir Motion X GPS Track” or go directly to http://bit.ly/Rx2qVp. Open the map. This map shows a track that I collected around Kendrick Reservoir in Colorado USA. This map was symbolized on the time of GPS collection, from yellow to gradually darker blue dots as time passed.
Note the components of the track to the northwest of the reservoir. These pieces were generated when the smartphone was just turned on and the track first began, indicated by their yellow color. They are erroneous segments and track points. Notice how the track cuts across the terrain and does not follow city streets or sidewalks. Change the base map to a satellite image. Cutting across lots would not have been possible on foot given the fences and houses obstructing the path. When I first turned on the smartphone, not many GPS satellites were in view of the phone. As I kept walking and remained outside, the phone recorded a greater number of GPS satellites, and as the number of satellites increased, the triangulation was enhanced, and the positional accuracy improved until the track points mapped closely represented my true position on the Earth’s surface.
Use the distance tool in ArcGIS Online to answer the following question: How far were the farthest erroneous pieces from the lake? Although it depends on where you measure from, some of the farthest erroneous pieces were 600 meters from the lake. Click on each dot to access the date and time each track point was collected. How long did the erroneous collection continue? Again, it depends on which points you select, but the erroneous components lasted about 10 minutes. At what time did the erroneous track begin correctly following my walk around the lake? This occurred at 11:12 a.m. on the day of the walk. [Take note of the letters I drew along the southwest shore of the reservoir!]
This simple example points to the serious concern about the consequences of using data without being critical of its source, spatial accuracy, precision, lineage, date, collection scale, methods of collection, and other considerations. Be critical of the data, even when it is your own!
The Un-Spider Knowledge Portal (United Nations Platform for Space-based information for Disaster Management and Emergency Response) recently reported the launch of the Bhuvan Ganga web portal and the Bhuvan Ganga mobile application. This new monitoring initiative will use existing geospatial information and crowd-sourced reporting to monitor pollution levels in the River Ganga (Ganges). The data portal already provides access to a variety of geospatial information including as flood hazard zones and environmental data and visitors to the site will be able to contribute to the project by uploading shapefiles and WMS layers. The accompanying mobile app will also allow users to collect and report information on pollution sources affecting water quality in the River Ganga basin.
The host geospatial platform, Bhuvan, was one of the projects we discussed in The GIS Guide to Public Domain Data. Impressed by geospatial resources such as Google Earth but concerned about potential misuses of the information following the terrorist attacks in Mumbai in 2008, the Indian Government launched its own version, describing Bhuvan as a gateway to the geospatial world. The benefits of providing open access to national, regional and local geospatial information outweighed lingering concerns over potential future attacks. Over the last seven years the site has developed into a comprehensive resource of geospatial datasets and services.
One of the most robust data portals is The Open Geoportal (OGP). It is a collaboratively developed, open source, federated web application framework to rapidly discover, preview and retrieve geospatial data from multiple curated repositories. The Open Geoportal Federation is a community of geospatial professionals, developers, information architects, librarians, metadata specialists and enthusiasts working together to make geospatial data and maps available on the web and contribute to global spatial data infrastructure. Patrick Florance at Tufts University and others have been diligently working to make this resource one that will be valued and useful for the GIS community for years to come. The project’s code repository is hosted on github. Documentation can be found here. To search the repository, you can enter information using the “where” and/or “what” search fields or zoom in on a location using the map,
Like any large data depository, this one takes some getting used to–but I found it to be straightforward: You enter where you are interested in searching, and what you are interested in searching for. Where and What: It doesn’t get much more straightforward than that. The only thing I could not get to work was the “Help” link on the page. After selecting and viewing your data on the map, you add it to a Cart. The Cart acts like something you would see on Amazon, and you can add to it and delete from it as you are searching, which I found to be quite convenient. Another nice touch is that you can adjust the symbology of the data that you are examining on the map before you download it. Even better, you can stream web services directly to your desktop, web, or mobile applications from the Cart. After you have made your selections, you access your Cart, whereupon you are presented with download options. If a layer is restricting by licensing agreement, you can add them to the cart but you must log in to preview or download restricted layers. Spending time with the OpenGeoportal will be well worth it given its ease of use, but moreso for the thousands of international data layers accessible here.
Additional tools that the OpenGeoPortal community is in the process of building include a Harvester–an open source web application that provides the automation of customized harvesting from partner metadata nodes and XML metadata files within a web or local directory. Also in progress is a Metadata Toolkit–a publicly available website that provides tools to easily create guided, geospatial metadata, and a Dashboard to analyze and visualize massive spatial data collections.
The European Space Agency (ESA) recently launched their latest environmental monitoring satellite, Sentinel-2A, adding high-resolution optical imaging capability to the radar imagery provided by the first satellite in the Copernicus fleet, Sentinel-1A. Tasked with combining wide swaths and short revisit times (5-day cycle), Sentinel-2A will monitor land and vegetation change to deliver a range of data products including land cover maps and indices for a number bio-geophysical variables. Although the commissioning phase will last for about three months, Sentinel-2A has already recorded its first images.
Once operational, Sentinel-2A’s imagery will be hosted on the Sentinels Scientific Data Hub, which will be upgraded shortly to accommodate the new satellite. The data will be available on a ‘free and open’ basis to any users registered with the data hub. Although the data will be made publicly available, they will not be in the public domain and remain the intellectual property of Copernicus Programme. However, subject to the ESA’s terms and conditions, users are free to user, alter, modify, publish and distribute the data. Judging by the first data samples, Sentinel-2A’s imagery will provide an invaluable resource for global environmental monitoring.