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Archive for November, 2014

Track on Track: Reflections on GPS Accuracy on a Running Track

November 23, 2014 1 comment

Recently, while at the Applied Geography Conference in Atlanta, I decided to test the spatial accuracy of my smartphone’s GPS in a challenging environment–a rooftop running track.  Although located on a roof, the track was surrounded by buildings far taller, and in downtown Atlanta, a location with many other buildings impeding signals from GPS, wi-fi hotspots, and cell phone towers. A further challenge to the GPS positional accuracy was that each lap on the track was only 0.10 miles (0.16 km), and therefore, I would not travel very far across the Earth’s surface.

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 of it in ArcGIS Online.  As I expected, the track’s position was compromised by the tall buildings–I only had a view of about half the sky during my time on the roof.  As you can measure for yourself on the map linked above, the track lines formed a band about 15 meters wide, but interestingly, were more spatially precise along the eastern side of the track, where the signal was better, as you can see in my video that I recorded at the same time.

Also, as I have encountered numerous times in the past, a line about 100 meters long stretches to the north.  Rest assured that I did not leap off  the building, but rather, the first point that the GPS app laid down as I opened the doors to walk outside was about a block away.  Then, 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 accurate that point is spatially.

Track on Track:  Reflections of GPS Accuracy on a Running Track

Track on Track: Reflections of GPS Accuracy on a Running Track.

Another interesting aspect of this study is that if the basemap is changed to satellite imagery, it appears that the track overlaps the tall building to the west.  Try it, using the map link above.  However, a closer investigation reveals that this is a result of the orthocorrection that was performed on the imagery; the buildings do not appear from “straight overhead”, but rather, they “fall away” to the east.  Turn this into another teachable moment:  Images, like maps, are not perfect, but they are very useful.  We can learn to manage error and imperfection through critical thinking and through the use of geotechnologies.  This is a central topic of our book and of this blog.

To dig deeper into issues of GPS track accuracy, see my related post 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 and here.

Despite these challenges, overall, I was quite pleased with my track’s spatial accuracy, even more so considering that I had the phone in my pocket most of the time I was walking.

Making the most of our personal location data

November 17, 2014 1 comment

We have written much over the last couple of years about location data privacy concerns and potential harm in publishing too much of our personal location data, however unintentionally. Despite these concerns, having access to aggregate personal location data can reveal patterns in behaviour that may have previously gone unnoticed.

In this short video (8.32 mins), Margaret McKenna (Runkeeper) discusses some of the issues, challenges and opportunities that arise collating and analysing the volumes of personal location tracking data that fitness enthusiasts have been capturing over recent years. The insights derived from the analysis into regional and city-wide exercise patterns and motivations have the potential to make a positive impact on communities.

 

 

 

UAVs Prohibited in National Parks in the USA

November 10, 2014 2 comments

As we state in our book, The GIS Guide to Public Domain Data, oftentimes, technological advancement and adoption proceeds at a faster pace than regulations accompanying it.  A perfect example is what is probably the hottest technology in remote sensing right now, and that is UAVs, or Unmanned Aerial Vehicles.  The Internet is becoming rapidly filled with stories and videos of footage from UAVs deployed by aerial survey companies, but even more commonly, operated by the general public.  For example, this storymap contains footage of UAV imagery flown over a rocket launch, a cruise ship, and more.

While I as a geographer are fascinated by these images and videos, I am at the same time sensitive to the myriad of privacy and safety issues raised by the operation of UAVs.  We are beginning to see laws passed to regulate the operation of UAVs on certain lands, such as the recent policy directive against flying these in national parks in the USA.

Jonathan Jarvis, director of the National Park Service, said that “We embrace many activities in national parks because they enhance visitor experiences with the iconic natural, historic and cultural landscapes in our care.  However, we have serious concerns about the negative impact that flying unmanned aircraft is having in parks, so we are prohibiting their use until we can determine the most appropriate policy that will protect park resources and provide all visitors with a rich experience.”  Some parks had already initiated bans after noise and nuisance complaints from park visitors, an incident in which park wildlife were harassed, and park visitor safety concerns.  For example, earlier this year, visitors at Grand Canyon National Park gathered for a quiet sunset were interrupted by a loud unmanned aircraft flying back and forth and eventually crashing in the canyon. Volunteers at Zion National Park witnessed an unmanned aircraft disturb a herd of bighorn sheep, reportedly separating adults from young animals.

The policy memorandum directs park superintendents to take a number of steps to exclude unmanned aircraft from national parks. The steps include drafting a written justification for the action, ensuring compliance with applicable laws, and providing public notice of the action.  The memorandum does not affect the primary jurisdiction of the Federal Aviation Administration over the National Airspace System.

The policy memorandum is a temporary measure, and it seems like a wise move. Jarvis said the next step will be to propose a Servicewide regulation regarding unmanned aircraft. That process can take considerable time, depending on the complexity of the rule, and includes public notice of the proposed regulation and opportunity for public comment.  The National Park Service may use unmanned aircraft for administrative purposes such as search and rescue, fire operations and scientific study. These uses must also be approved by the associate director for Visitor and Resource Protection.

Near the Esri office in Colorado a month ago, I witnessed my first UAV flight where I did not know who was operating the vehicle.  I’m sure we will look back in years to come and realize that we in 2014 were at the dawn of a technology that will no doubt transform GIS and our everyday lives.   I anticipate sensors soon capable of capturing imagery in a wide variety of wavelengths, as well as atmospheric and other types of sensors that will further hasten the era of big data.  I am hopeful that we will chart a prudent course through the advent of UAVs, taking advantage of the innumerable benefits that UAVs can offer the GIS industry and also society as a whole.

Meeting the challenge of up-to-the-minute maps

November 3, 2014 Leave a comment

A few weeks ago we wrote about autonomous cars and some of the associated location data privacy issues that this new type of transport raised. In a related article in Automotive News, the challenge of collecting and maintaining the highly accurate map data that would be required to support these vehicles and provide the locational context for the various data sources collected by in-car sensors was also discussed. As the report author commented, ‘History’s most intrepid explorers were often at the mercy of their maps. The self-driving cars of the future won’t be any different.

Jim Keller (Chief Engineer, Honda R&D Americas Inc.) has acknowledged that mapping is going to be critical to the success of the autonomous car and he considers the relationship between map makers and car manufacturers as both vital and symbiotic. He argues that data collected by the cars will augment the data available from more traditional sources and data available from those more traditional sources will in turn help the car manufacturers.

While this suggests a new location data collecting dynamic – crowd-sourcing meets Street View, with cars altruistically recording and sharing the data they collect – it also highlights some of the challenges ahead. These cars have the potential to provide unprecedented volumes of detailed road network data but for that data to be useful, they have to be accurate, current and consistent with the standards adopted by other map data providers to ensure integration with existing data sets, reliability and ultimately safe driving for all road users.