Data quality is a central theme of this blog and our book. Here, we focus on quality of geospatial information, which is most often in the form of maps. One of my favorite maps in terms of the richness of information and the choice of symbology is this “simple map of future population growth and decline” from my colleague at Esri, cartographer Jim Herries. Jim symbolized this map with red points indicating areas that are losing population and green points indicating areas that are gaining population. This map can be used to learn where population change is occurring, down to the local scale, and, with additional maps and resources, help people understand why it is changing and the implications of growth or decline.
But the map can also be an effective tool to help people understand issues of data collection and data quality. Pan and zoom the map until you see some rivers, lakes, or reservoirs, such as Littleton Colorado’s Marston Reservoir, shown on the map below. If you zoom in to a larger scale, you will see points of “population” in this and nearby bodies of water. Why are these points shown in certain lakes and rivers? Do these points represent “aqua people” who live on houseboats or who are perpetually on water skis, or could the points be something else?
The points are there not because people are living in or on the reservoir, but because the dots are randomly assigned to the statistical area that was used. In this case, the statistical areas are census tracts or block groups, depending on the scale that is being examined. The same phenomena can be seen with dot density maps at the county, state, or country level. And this phenomenon is not confined to population data. For example, dot density maps showing soybean bushels harvested by county could also be shown in the water, as could the number of cows or pigs, or even soil chemistry from sample boreholes. In each case, the dots do not represent the actual location where people live, or animals graze, or soil was tested. They are randomly distributed within the data collection unit. In this case, at the largest scale, the unit is the census block group, and randomly distributing the points means that some points fall “inside” the water polygons.
Helping your colleagues, clients, students, or some other audience you are working with understand concepts such as these may seem insignificant but is an important part of map and data interpretation. It can help them to better understand the web maps that we encounter on a daily basis. It can help people understand issues and phenomena, and better enable them to think critically and spatially. Issues of data collection, quality, and the geographic unit by which the data was collected–all of these matter. What other examples could you use from GIS and/or web based maps such as these?
The Census Business Builder app and the Opportunity Project are two new tools from the US Census Bureau that make accessing and using data, and, we hope, making decisions from it, easier for the data analyst. Both of these applications are good representatives of the trend we noted in our book and in this blog— the effort by government agencies to make their data more user-friendly. While I would still like to see the Census Bureau address what I consider to be the still-cumbersome process of downloading and merging data from the American Community Survey and the Decennial Census with the TIGER GIS files, these two efforts represent a significant step in the right direction. While GIS users may still not be fully satisfied by these tools, the tools should expand the use of demographic, community, and business data by non-GIS users, which seems to be sites’ goal.
The Opportunity Project uses open data from the Census Bureau and from communities along with a Software Development Kit (SDK) to place information in the hands of decision makers. Because these decision makers are not likely to be familiar with how to conduct spatial analysis within a GIS, the appeal of this effort is for wiser decision making with the geographic perspective. A variety of projects are already on the site to spark ideas, including Streetwyze, GreatSchools, and Transit Analyst.
The Census Business Builder is a set of web based mapping services that provides selected demographic and economic data from the Census Bureau. You can use it to create customized maps and county and city level reports and charts. A small business edition presents data for a single type of business and geography at a time, while the regional analyst edition presents data for all sectors of the economy and for one or more counties at a time. These tools are based on Esri’s online mapping capabilities and offer some of the functionality of Esri’s Business Analyst Online. Give them a try and we look forward to your comments below.
One of the most useful sites of the past 15 years for GIS users, in my judgment, has been the National Atlas of the United States. It contains a “map maker” that allows you to create online maps of climate, ecoregions, population, crime, geology, and many other layers, and a “map layers” repository that houses all of the raster and vector data layers that are displayable in the map maker. All of those hundreds of layers are downloadable in standard formats that are easy to use with GIS.
Sadly, the National Atlas is scheduled to disappear on 30 September 2014. According to the transition FAQ, “the National Atlas and The National Map will transition into a combined single source for geospatial and cartographic information. This transformation is projected to streamline access to maps, data and information from the USGS National Geospatial Program (NGP). This action will prioritize our civilian mapping role and consolidate core investments while maintaining top-quality customer service.” Thus, the National Map is scheduled to be the content delivery mechanism for the National Atlas content.
But, data users take note: Not all of the National Atlas content is migrating to the National Map. According to the FAQ’s question of “Will I still be able to find everything from the National Atlas on The National Map web site”, the answer is, “No. Most National Atlas products and services that were primarily intended for a broad public audience as well as thematic data contributions from outside the National Geospatial Program (NGP) will not be available from nationalmap.gov.”
I think this is most unfortunate news. In my opinion, and that of many students and educators that I work with in courses and institutes, and the other data users I have worked with over the years, the National Map is almost as clunky and difficult to use as it was 10 years ago. I use it frequently because it is still one of the richest sources of data, but it is by no means easy to obtain that data. And equally importantly, it serves a different audience than the National Atlas does. Yes, the National Atlas viewer is dated, but it requires little bandwidth, making it accessible to schools and other institutions contending with poor connectivity. How much effort is required just to leave national atlas alone and leave it online, with an understanding that it will not be updated?
In an era where more geospatial data are needed, not less, and improved geographic literacy is increasingly critical to education and society, the disappearance of the National Atlas seems like a giant step backward.
Due to a lack of mapping resources and difficulties in obtaining census statistics for many Asian countries, the AsiaPop project was set up in July 2011 to produce detailed and freely available population distribution maps for the whole of Asia. The project recently announced the next release of population distribution datasets for 17 Asian countries, including Sri Lanka, Nepal, North and South Korea and Tajikistan. The data, available in GeoTIFF format, are available to download for free (subject to registration) and provide population count data (persons per square) for 2010 and 2015.
A combination of high-resolution (100m) settlement maps derived from satellite imagery and land cover maps were used to reallocate contemporary census-based population data, producing more accurate national cover than had been previously available. The datasets are used to measure the impact of population growth, monitoring change and as a basis for future development strategies.
A related project was established in Africa in 2009 (http://www.afripop.org/), also providing free population count data (in Esri FLOAT format).
AmeriPop, started in Oct 2012, aims to provide similar data for Central and South America (http://www.ameripop.org/).