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Posts Tagged ‘resolution’

Understanding Data: It is Critical!

November 22, 2015 1 comment

Think of spatial data as the fuel for your GIS engine.  It is fundamental to any spatial analysis.  On listservs, LinkedIn, GeoNet, in this blog, other blogs, and in our book, discussions about data are commonplace.  The volume of spatial data available has increased dramatically in recent years as have the formats in which that data is stored, and the means by which that data is delivered to the user—via web-mapping services, servers, portals, media, user-defined boxes, predefined tiles, and more.

In this avalanche of spatial data, it is more important than ever to encourage your users to fully understand the data they are using. Sometimes, stakeholders view anything on the computer as accurate and complete, including maps.  Maps are incredibly useful, but inherently full of errors and distortions, from the map projection they are drawn from, to missing data, to generalized lines.  Nowadays, anyone can make a digital map.  Help your the users of your data understand that data quality affects subsequent analysis.  For example, in a lesson I frequently teach on plate tectonics, I ask students to study 2001’s largest earthquake, below (south of) the tip of the arrow:

Using a measure tool, students determine that the earthquake is 4 kilometers off of the coast of Peru.  But then I ask them to consider the fact that the generalized coastline was digitized at 1:30,000,000 scale.  How confident are we based on this shoreline that the earthquake was offshore?  Consider the classic geography problem of calculating the length of the British (or any) coastline—the more detailed the scale, the longer the coastline becomes, because at larger and larger scales, the coastline begins to include every cape and bay.  Peru’s coastline may actually twist and turn here, so the earthquake could have occurred on the beach.  The “so what” and spatial thinking discussion continues with the impacts of coastal earthquakes versus underwater quakes, and possible tsunamis.

Encourage your data users – whether they are students, customers, managers, the general public, or others – to be critical of spatial data—knowing its source, who produced it, when and why it was produced, the scale at which it was produced, and its content.   Show them how to create and access metadata.   They will then be able to critically evaluate spatial information and decide whether they will use it in their present and future decision making.  And it is my hope that when they produce their own data, that they will tag and document it thoroughly.

A United Nations resolution on geospatial data

May 31, 2015 2 comments

During their 69th General Assembly, the United Nations passed a resolution on a “global geodetic reference frame for sustainable development“.   This resolution reaffirmed earlier endorsements of resolutions (1) concerning transport, search, and rescue operations that depend on GNSS, (2) concerning coordination among global observing systems and programs, including remote sensing efforts, and (3) concerning geospatial information for sustainable development policymaking, programming, and project operations.

Specifically with regard to work with geodetic reference frames, the resolution “recognized the economic and scientific importance of and the growing demand for an accurate and stable global geodetic reference frame for the Earth that allows the interrelationship of measurements taken anywhere on the Earth and in space, combining geometric positioning and gravity field-related observations, as the basis and reference in location and height for geospatial information, which is used in many Earth science and societal applications, including sea -level and climate change monitoring, natural hazard and disaster management and a whole series of industrial applications (including mining, agriculture, transport, navigation and construction) in which precise positioning introduces efficiencies.”  The resolution also recognizes “the extraordinary achievements made by [many organizations] in measuring and monitoring changes in the Earth’s system on a best-effort basis, including the development of the now adopted International Terrestrial Reference Frame.”

It recognizes “the investments of Member States in developing satellite missions for positioning and remote sensing of the Earth, supporting a range of scientific endeavours that improve our understanding of the “Earth system” and underpin decision-making, and recognizing that the full societal benefits of these investments are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels.”  It acknowledges that “the global geodetic reference frame depends upon the participation of countries all around the globe, and the need to take action to strengthen international cooperation.”  The UN mentioned a Committee of Experts on Global Geospatial Information Management to develop a global geodetic road map that addresses key elements relating to the development and sustainability of the global geodetic reference frame.

The resolution encourages UN Member States and other relevant international organizations to enhance global cooperation in providing technical assistance, especially for capacity development in geodesy for developing countries, with the aim of ensuring the development, sustainability and advancement of a global geodetic reference frame.  It urges Member States to implement open sharing of geodetic data, standards and conventions, on a voluntary basis, (which we discuss in this blog frequently) to contribute to the global reference frame.”  As an educator, I was especially glad to see that the resolution “invites Member States to develop outreach programmes that make the global geodetic reference frame more visible and understandable to society.”

To move the GIS field forward, and to ensure that geospatial data is available and is shared, we need grass roots efforts, but also recognition from high level organizations.  These statements from the UN are welcomed, and it is our hope that the Member States will take these resolutions seriously and translate them into actionable items in their own countries and across countries to grapple with the 21st Centuries all around us — almost all of which transcend borders.

A global geodetic reference frame for sustainable development from the United Nations.

A global geodetic reference frame for sustainable development from the United Nations.

Walking on Water? Revisiting Reflections on Resolution and Scale

May 17, 2015 1 comment

A few years ago, I walked on the pier at Manitowoc, Wisconsin, and after mapping my route, reflected on issues of resolution and scale in this blog.  After recording my track on my smartphone in an application called RunKeeper, it appeared on the map as though I had been walking on the water!  This, of course, was because the basemap did not show the pier or the fill adjacent to the marina.  Recently, following the annual meeting of the Association of American Geographers, I had the opportunity to retrace my steps and revisit my field site.  What has changed in the past 2 1/2 years?  Much.

As shown below, the basemap used by RunKeeper  has vastly improved in that short amount of time.  The pier and fill is now on the map, and note the other differences between the new map and the one from 2012 below that appears below it–schools, trails, contour lines, and other features are now available.  A 3-D profile is available now as well. Why?  The continued improvement of maps and geospatial data from local, regional, federal, and international government agencies plays a role.  We have a plethora of data sources to choose from, as is evident in our recent post about Dr Karen Payne’s list of geospatial data and the development of Esri’s Living Atlas of the World.  The variety and resolution of base maps in ArcGIS Online and in other platforms continues to expand and improve at an rapid pace.

Equally significant, and some might argue more significant, is the role that crowdsourcing is having on the improvement of maps and services (such as traffic and weather feeds). In fact, even in this example, note the “improve this map” text that appears in the lower right of the map, allowing everyday fitness app users the ability to submit changes that will be reviewed and added to RunKeeper’s basemap. What does all of this mean for the the data user and GIS analyst? Maps are improving at a dizzying pace due to efforts by government agencies, nonprofit organizations, academia, private companies, and the ordinary citizen.  Yet, scale and resolution still matter.  Critically thinking about data and where it comes from still matters.  Fieldwork that uses ordinary apps can serve as an effective instructional technique.  It is indeed an exciting time to be in the field of geotechnologies.

Walking on Water?  Reflections on Resolution and Scale, Part 2

Walking on Water? Reflections on Resolution and Scale, Part 2. My walk on the north pier at Manitowoc, Wisconsin.

The map from 2012 is below.

Map from 2012 of my same route on the pier.

Map from 2012 of my same route on the pier.

Walking On Water? Reflections on Resolution and Scale

December 16, 2012 1 comment

I recently gave presentations at the University of Wisconsin Milwaukee for GIS Day, and took the opportunity, as most geographers would, to get out onto the landscape. I walked on the Lake Michigan pier at Manitowoc, enjoying a stroll in the brisk wind to and from the lighthouse there, recording my track on my smartphone in an application called Runkeeper. When my track had finished and been mapped, it appeared as though I had been walking on the water!

Walking on Water?  My track on the map

Walking on Water? My track on the map.

Lighthouse on pier

Lighthouse on the end of the pier.

According to my map, I walked on water. Funny, but I don’t recall even getting wet! It all comes down to paying close attention to your data, and knowing its sources. This provides a teachable moment in a larger discussion on the importance of scale and resolution in any project involving maps or GIS. In my case, even if I scrolled in to a larger scale, the pier did not appear on the Runkeeper’s application’s base map. It does, however, appear in the base map in ArcGIS Online.

In the book that Jill Clark and I wrote entitled The GIS Guide to Public Domain Data, we discuss how scale and resolution can be conceptualized and put into practice in both the raster and vector worlds. We cite examples where neglecting these important concepts have led not only to bad decisions, but have cost people their property and even their lives.  Today, while GIS tools allow us to instantly zoom to a large scale, the data being examined might have been collected at a much smaller scale.  Much caution therefore needs to be used when making decisions when the analysis scale is larger than the collection scale.  For example, if you are making decisions at 1:10,000 scale and your base data was collected at 1:50,000 scale, you are treading on dangerous ground.

Or, one could say, you are “walking on water”!