OpenLayers is a great resource for those wanting to put a map on the web. Simply put, OpenLayers "is a pure JavaScript library for displaying map data in most modern web browsers, with no server-side dependencies." Many posts ago, I used OpenLayers to post a web map.
New features will include a more accessible API and a host of other features. An alpha version is currently available for download: https://github.com/openlayers/ol3/releases/tag/r3.0.0-alpha.4
If you have not seen OpenLayers libraries before be sure to check out: http://openlayers.org/.
Monday, July 29, 2013
Monday, July 8, 2013
AIDSVu Map Provides Better National View of the Epidemic
AIDSVu Map provides the "most detailed publicly available view of HIV prevalence in the United States" It is a "compilation of interactive online maps that display HIV prevalence data at the national, state and local levels and by different demographics, including age, race and sex."
Estimates of the prevalence of persons living with HIV go from the state and county level down to ZIP codes and census tracts in the United States. AIDSVu was produced by the Emory School of Public Health. In addition, it provides aggregate data for download and use. The website uses OpenStreetMap. Click either of the screenshots below to enlarge them.
In addition, the group does a good job explaining the methods for protecting patient privacy--avoiding cases where a person's identity may be surmised from sparse population, data, or a combination of circumstances.
However, it would be nice to see some spatial analysis doneor overlays with socioeconomic data to help the viewer understand patterns. Overall, the map performs very well on the web. Zooming-in is relatively straightforward and the map renders well--but is quite flicker-y. Maybe a projection issue? It is good to see some agencies using census tracts over ZIP codes because of the ease to link them to Census and American Community Survey (ACS) Data.
Estimates of the prevalence of persons living with HIV go from the state and county level down to ZIP codes and census tracts in the United States. AIDSVu was produced by the Emory School of Public Health. In addition, it provides aggregate data for download and use. The website uses OpenStreetMap. Click either of the screenshots below to enlarge them.
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| An Overview of Several Cities |
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| The Epidemic in Houston |
However, it would be nice to see some spatial analysis doneor overlays with socioeconomic data to help the viewer understand patterns. Overall, the map performs very well on the web. Zooming-in is relatively straightforward and the map renders well--but is quite flicker-y. Maybe a projection issue? It is good to see some agencies using census tracts over ZIP codes because of the ease to link them to Census and American Community Survey (ACS) Data.
Sunday, June 2, 2013
USGS Seamless ArcGIS Toolbar
Paid and free and open-source software (FOSS) and data do not have to work in isolation. One example is the USGS ArcGIS Toolbar (for versions 9.3 and 10) that allows users to seamlessly download data from the USGS into ArcGIS.
As stated on the USGS website:
"The purpose of the enhanced tools are to allow the user to define an area of interest (AOI), select products or options for downloading products, and then download the product to a local disk. The capabilities available in ArcMap would allow for more client options: add preview, index and outline layers, template selection, reprojection, and import the downloaded products into the current map overlay. All of this can be done without leaving the ArcMap environment. With the functions included with the ArcGIS toolbox, users may allow for client-side scripting, model-building, and easier integration in local ArcGIS based development."
It beats hopping from different websites, waiting and moving downloads, checking your e-mail, and all of those other activities preventing you from getting work done!
Check it out here and give it a try!: http://cumulus.cr.usgs.gov/toolbar.php
As stated on the USGS website:
"The purpose of the enhanced tools are to allow the user to define an area of interest (AOI), select products or options for downloading products, and then download the product to a local disk. The capabilities available in ArcMap would allow for more client options: add preview, index and outline layers, template selection, reprojection, and import the downloaded products into the current map overlay. All of this can be done without leaving the ArcMap environment. With the functions included with the ArcGIS toolbox, users may allow for client-side scripting, model-building, and easier integration in local ArcGIS based development."
It beats hopping from different websites, waiting and moving downloads, checking your e-mail, and all of those other activities preventing you from getting work done!
Check it out here and give it a try!: http://cumulus.cr.usgs.gov/toolbar.php
Tuesday, May 28, 2013
TileMill and MapBox
Publishing a map on the web can be accomplished through many different ways and programs. Costs, ranging from free to expensive, are mostly based on the popularity of the map (i.e. number of views) as well as how much information is stored to create the map. Performance of the map can also be a key component to cost.
MapBox, a website, and it associated downloadable tool, TileMill, are a great way to create a visually appealing, interactive, and quickly deployable map. The fully interactive map is available here. The map below works correctly in Firefox.
A screenshot below shows the TileMill program with an example of easy coding on the right-hand side. If you decide to give TileMill a try, be sure to check out its Crash Course!
MapBox, a website, and it associated downloadable tool, TileMill, are a great way to create a visually appealing, interactive, and quickly deployable map. The fully interactive map is available here. The map below works correctly in Firefox.
A screenshot below shows the TileMill program with an example of easy coding on the right-hand side. If you decide to give TileMill a try, be sure to check out its Crash Course!
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| Screenshot of TileMill |
Saturday, May 18, 2013
Census Data: Easier to Use
The Census Bureau
has come a long way by offering census data in formats that can be
easily imported into GIS software. Whether at small or large scales,
census data are vital to any analysis. Of course, census data are free,
even though some companies charge! In addition, it is noteworthy to
add census data can be ordered on DVD and includes user friendly tools
to help extract the data you need.
Previously, and in still in some cases, attribute data would have to be joined with shapefiles. The TIGER/Line page now features demographic and social data pre-joined to shapefiles and geodatabases for users that are not familiar with joining and managing such complex data. Click the map below to enlarge it.
Data from the American Community Survey (ACS) 5-year estimates can also be downloaded easily. However, more can be done and more ready-to-use files could be created--resources allowing! Hopefully, the Census will be able to maintain what they are doing and expand in the future.
Maps made with QGIS
Previously, and in still in some cases, attribute data would have to be joined with shapefiles. The TIGER/Line page now features demographic and social data pre-joined to shapefiles and geodatabases for users that are not familiar with joining and managing such complex data. Click the map below to enlarge it.
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| US Population Counts by County and Cities with Population Greater than 250,000 |
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| Family Size (Purple/Red = Greater than 1 Standard Deviation above the mean, Blue = Below, No Color = Mean to 1 SD Above). Both maps are derived from data in the Summary Demographic Profile 1. |
Sunday, May 5, 2013
Space-Time Cluster Analysis with SatScan
For more information: Visit the latest post on SatScan: http://opensourcegisblog.blogspot.com/2015/02/satscan-94-released-better-than-ever.html
Original post
Numerous basic and advanced techniques exist for finding spatial and temporal clusters. Searching for clusters has broad applications for any field of scientific inquiry!
Unlike other spatial models in other free and paid software, SatScan's statistics' probability distributions allow for poisson (count data and rates) and binomial distributions--to name two. There is also the ability to treat same data as continuous. You won't find an easier way to do this than with SatScan!
SatScan is a free program but requires several steps to get data into it for analysis. For most analyses you will need three files in a text delimited format -- without column headers (such as variable names).
The three files: 1) A case file with a column for the geographic unit. day, month or year (see documentation), and number of cases. You can aggregate the data into any geographic unit--large or small. 2) A geographic coordinate file (cartesian or lat/long) with the name of the unit (i.e. census tract), x and y for centroids of the geographic units, and 3) population file with the estimated population over the time period-- by year.
After this slightly painful process, which one learned, can easily be duplicated, one can easily perform complex spatial analysis and adjust key parameters such as the population at risk and maximum size of the cluster. Time units are important, and you will have to make key decisions as to how long a cluster may have to develop--depending on the problem of interest.
SatScan can look for purely spatial, purely temporal, space-time, and spatial variation in temporal trends in data. SatScan uses 'scan' statistics/scanning window and cylinder to finding and differentiating potential clusters.
SatScan's output includes *.txt and/or *.dbf files of the results and clusters. The *.gis file can be joined to the shapefile of the geographic units, which are using, to show risks and different clusters. This part is straightforward and less painful. You will need to take your time selecting parameters and interepreting results!
Two good articles to read are: 1) Block's Tutorial and Review and 2) Visual Analytics of Space-Time Statistics. The SatScan manual on its website also has a great list of references.
Additional Article:
http://medicine.plosjournals.org/archive/1549-1676/2/3/pdf/10.1371_journal.pmed.0020059-L.pdf
Original post
Numerous basic and advanced techniques exist for finding spatial and temporal clusters. Searching for clusters has broad applications for any field of scientific inquiry!
Unlike other spatial models in other free and paid software, SatScan's statistics' probability distributions allow for poisson (count data and rates) and binomial distributions--to name two. There is also the ability to treat same data as continuous. You won't find an easier way to do this than with SatScan!
SatScan is a free program but requires several steps to get data into it for analysis. For most analyses you will need three files in a text delimited format -- without column headers (such as variable names).
The three files: 1) A case file with a column for the geographic unit. day, month or year (see documentation), and number of cases. You can aggregate the data into any geographic unit--large or small. 2) A geographic coordinate file (cartesian or lat/long) with the name of the unit (i.e. census tract), x and y for centroids of the geographic units, and 3) population file with the estimated population over the time period-- by year.
After this slightly painful process, which one learned, can easily be duplicated, one can easily perform complex spatial analysis and adjust key parameters such as the population at risk and maximum size of the cluster. Time units are important, and you will have to make key decisions as to how long a cluster may have to develop--depending on the problem of interest.
SatScan can look for purely spatial, purely temporal, space-time, and spatial variation in temporal trends in data. SatScan uses 'scan' statistics/scanning window and cylinder to finding and differentiating potential clusters.
SatScan's output includes *.txt and/or *.dbf files of the results and clusters. The *.gis file can be joined to the shapefile of the geographic units, which are using, to show risks and different clusters. This part is straightforward and less painful. You will need to take your time selecting parameters and interepreting results!
Two good articles to read are: 1) Block's Tutorial and Review and 2) Visual Analytics of Space-Time Statistics. The SatScan manual on its website also has a great list of references.
Additional Article:
http://medicine.plosjournals.org/archive/1549-1676/2/3/pdf/10.1371_journal.pmed.0020059-L.pdf
Tuesday, April 30, 2013
Files, Files Everywhere!
Naming, organizing, and accessing files during any type of analysis or project is always a challenge. The most recent release of QGIS features a file browser to help create and manage different types of geospatial data and is akin to ArcCatalog. After installing QGIS, you will notice a second yellow "Q" icon--this is the shortcut to the browser.
In the example below, you will see a connection made to USGS Web Map Service (WMS) through the QGIS browser.
The browser can also be docked to QGIS so there is no need to re-open and close any windows.
In the example below, you will see a connection made to USGS Web Map Service (WMS) through the QGIS browser.
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| Finally, a way to organize all of these open GIS files! |
The browser can also be docked to QGIS so there is no need to re-open and close any windows.
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