Downloading and Using GIS Data from NM-IBIS
Once an IBIS query has been defined, Geographic Information System (GIS) data about the results can be downloaded for further analysis and visualization.
| Contents |
| 1. Downloading GIS data from IBIS 2. Using a GeoJSON in ESRI ArcMap 3. Using a GeoJSON in QGIS 4. Important Note About Downloaded IBIS GIS Data |
1. Downloading GIS data from IBIS
To download GIS data from IBIS, first create query that produces a map. In the upper right-hand corner of the map view, open the "Layers Control" menu (
).
A blue "Download Layer" button (
)will be visible next to the map layers that are available for download.
Clicking the 'Download' button opens another browser window displaying a wall of text. This text constitutes an array of feature definitions and coordinates that make up a GeoJSON file. GeoJSON is an open-source geospatial data interchange format based on JavaScript Object Notation (JSON).
To save the GeoJSON text as a file, copy all the text in the browser window and paste it into a generic word-processing program such as Notepad. Save the file, changing the file extension from the default (.txt) to .geojson.
The resulting .geojson file can be viewed and manipulated in GIS desktop software. ESRI's ArcMap is a widely used product, and the free, open-source program QGIS is another popular choice. Slightly different procedures are necessary to use a GeoJSON file with these programs.
2. Using a GeoJSON in ESRI ArcMap
GeoJSON files from IBIS cannot be directly opened in ArcMap; they must first be transformed into the ESRI shapefile format (.shp). Several options are available, but currently one of the easiest methods to transform IBIS GeoJSON files into shapefiles is to use the free, open-source, on-line transformation tool available here: http://ogre.adc4gis.com/.
Copy and paste the entirety of the .geojson text into the interface window. Download and unzip the resulting shapefile to your directory of choice, and load into ArcMap as usual.
3. Using a GeoJSON in QGIS
QGIS is a free, open-source GIS program licensed under the GNU General Public License. It runs on Linux, Unix, Mac OSX, Windows, and Android, and supports numerous vector, raster, and database formats and functionalities. The program can be downloaded at: http://www.qgis.org/en/site/.
After installation, two main GIS programs will be available: QGIS Browser and QGIS Desktop. QGIS Browser is a GIS file explorer (similar to Windows Explorer, but only displaying GIS-related files). QGIS Desktop is the program where data are displayed, symbolized, and analyzed.
In QGIS Desktop, the "Manage Layers" toolbar contains an "Add Vector Layer" button. Using that interface, navigate to the folder containing the .geojson and open the file. QGIS Desktop can open the .geojson directly, with no preliminary transformation being necessary. The .geojson can then be transformed to a different GIS file type (including shapefile) by right-clicking the layer name, and using the "Save vector layer as" command.
4. Important Note About Downloaded IBIS GIS Data
The boundaries of all the GIS layers that are displayed and downloaded from IBIS represent slightly generalized versions of the actual geographic areas. Using simplified polygons reduces overall file sizes, which helps keep the IBIS web-mapping service operating smoothly and responsively. These generalized geographies are perfectly suited to viewing data distributions at the map scales that are available in the online IBIS maps.
However, downloaded IBIS GIS boundaries are generalized, and do vary slightly from official US Census GIS data, for example (only on the order of several feet, in most cases). Hence, if more precise GIS spatial analysis and presentation is required, fully detailed GIS files of the DOH Small Areas, Health Regions, and other geographic subdivisions can be downloaded from ////UNDER CONSTRUCTION//// and used as master reference files in GIS desktop software. Tables from IBIS query results can be linked to these detailed GIS files to provide flexible spatial-data analysis and visualization opportunities.