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Using SAS® and Google Earth ™ to Access and Display Air Pollution Data

Using SAS® and Google Earth ™ to Access and Display Air Pollution Data. RTSUG Meeting September 10, 2008 Joshua Drukenbrod U.S. EPA Office of Air Quality Planning Standards drukenbrod.josh@epa.gov. Background. Purpose. Improve access to emissions information

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Using SAS® and Google Earth ™ to Access and Display Air Pollution Data

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  1. Using SAS® and Google Earth™ to Access and Display Air Pollution Data RTSUG Meeting September 10, 2008 Joshua Drukenbrod U.S. EPA Office of Air Quality Planning Standards drukenbrod.josh@epa.gov

  2. Background Purpose • Improve access to emissions information • Provide information in easy-to-use format • Provide direct link to data

  3. Previous “high-level” emissions pages on our web site… Background • Do not provide data in an “easy-to-use” format • Do not answer some of the most common questions • Do not provide the spatial, temporal, or sector-specific resolution many people need

  4. How are we changing that? Background • Linking the site directly to the data, providing… • National, state, and local summaries • Source category detail not previously available • Geospatial access not previously available

  5. SAS/IntrNet– What is it? How it Works • Component of SAS that enables dynamic access to programs and data via the Web • Anything you can program in SAS can be output to Web browser/Google Earth • Users don’t need to have SAS or know how to use SAS

  6. 1 2 4 3 5 How it Works SAS/IntrNet – How does it work? Web Page/Google Earth links to SAS service SAS program queries data Program generates results Data returns to program Workstation (Web Interface or Google Earth™) Database (Oracle, Access DB) Web Server (SAS/Internet®) Results displayed in Web browser or Google Earth placemark

  7. Getting Started Plotting Points and Coloring Counties • A SAS/IntrNet service must be set up to utilize online capabilities. • A quick read through Google’s KML Reference guide will help with the basics of creating custom kml files. • Data must include either (lat & long) or (county & state fips) for point plotting in Google Earth. • Determine variable for analysis when creating coloring counties. • Determine a “color scheme” for counties. • Data MUST include either (county & state) FIPS or (county & state) name when coloring counties.

  8. Getting Started Creating KML files • Output data to an external file using the file extension kml. • Data is output through a series of PUT statements. • KML support of HTML provides increased flexibility on how to display data in the placemark windows. • Using SAS to develop these kml files allows for more efficient coding and provides the abilities to plot conditionally. • SAS provides county perimeter coordinates when developing county colored kml files.

  9. Plotting Points • Step 1: Prepare data for creating kml files. • Standard cleaning of data. • Determine if placemark elevation is a feature you will like to use then determine variable to base elevation on. • Determine if data includes (lat & long) or (county & state fips).

  10. PlottingPoints • Step 2: Create kml file. Name your kml file in filename path: filename <fref> - <directory> ex. Filename kmlfile ‘C:\Documents and Settings\user\Desktop\mykml.kml Be sure to include .kml extension.

  11. Plotting Points (Step 2 cont’d) • Begin data step for creating kml. When creating kml files a basic format is used in kml writing. <?xml version=“1.0” encoding=“UTF-8”?> <kml xmlns=http://earth.google.com/kml/2.2> <Document> <Style id=“A”> <IconStyle> <scale>1</scale> <Icon> <href> “location if placemark icon” </href> </Icon> </IconStyle> </Style> <Placemark> <name>A name here</name> <StyleUrl>#A</StyleUrl> <Point> <extrude>1</extrude> <altitudeMode> (relativeToGround , clampedToGround or absolute) </altitudeMode> <coordinates>Long,Lat,Elevation </coordinates> </Point> </Placemark> </Document> <kml>

  12. Plotting Points (Step 2 cont’d) A sample SAS data step is: data _null_; file <fref>; set <dataset> end=last; if _n_ = 1 then do; put ‘<?xml version=“1.0” encoding=“UTF-8”?>’; put ‘<kml xmlns=http://earth.google.com/kml/2.2>’; put ‘<Document>’; put ‘<Style id=“A”>’; put ‘<IconStyle>’; put ‘<scale>1</scale>’; put ‘<Icon>’; put ‘<href> “location if placemark icon” </href>’; put ‘</Icon>’; put ‘</IconStyle>’; put ‘</Style>’; end;

  13. Plotting Points (Step 2 cont’d) After this initial step we must prepare the lat & longs for the kml file by removing white spaces. points = ‘<coordinates>’||trim(left(xcoord))||’,’||trim(left(ycoord))||’,0 </coordinates>’; Using the basic kml format and a put statement in SAS, we are able to plot our data in Google Earth. ………. put ‘<Placemark>’; put ‘ <name>A name here</name>’; put ‘ <StyleUrl>#A</StyleUrl>’; put ‘ <Point>’; put ‘ <extrude>1</extrude>’; put ‘ <altitudeMode> (relativeToGround or clampedToGround or absolute) </altitudeMode>’; put points; put ‘ </Point>’; put ‘ </Placemark>’; …………….

  14. Plotting Points • Step 3: Closing the kml file. Closing the kml file in SAS is as simple as opening the file: …………put ‘ <altitudeMode> (relativeToGround or clampedToGround or absolute) </altitudeMode>’; putpoints; put ‘ </Point>’; put ‘ </Placemark>’; ……………. if last then do; put ‘</Document>’; put ‘</kml>’;

  15. data _null_; file <fref>; set <dataset> end=last; if _n_ = 1 then do; put ‘<?xml version=“1.0” encoding=“UTF-8”?>’; put ‘<kml xmlns=http://earth.google.com/kml/2.2>’; put ‘<Document>’; put ‘<Style id=“A”>’; put ‘<IconStyle>’; put ‘<scale>1</scale>’; put ‘<Icon>’; put ‘<href> “location if placemark icon” </href>’; put ‘</Icon>’; put ‘</IconStyle>’; put ‘</Style>’; end; points = ‘<coordinates>’||trim(left(xcoord))||’,’||trim(left(ycoord))||’,0 </coordinates>’; put ‘<Placemark>’; put ‘ <name>A name here</name>’; put ‘ <StyleUrl>#A</StyleUrl>’; put ‘ <Point>’; put ‘ <extrude>1</extrude>’; put ‘ <altitudeMode> (relativeToGround or clampedToGround or absolute) </altitudeMode>’; putpoints; put ‘ </Point>’; put ‘ </Placemark>’; if last then do; put ‘</Document>’; put ‘</kml>’; end; run;quit;

  16. Writing in Description Balloons Very simple knowledge of html is required along with a few extra lines of code. ……………………. put '<Placemark>'; put '<description>'; put '<![CDATA['; put (Any html coding is done between the line above and below); put ']]>'; put '</description>'; …………………….

  17. Using SAS/Intrnet Service Place link to service within the description tag. ……………………. put '<Placemark>'; put '<description>'; put '<![CDATA['; link='<img src="http://www.epa.gov/cgi-bin/broker?_service=data'|| '&_program=dataprog.<Name of Program>.sas'|| '&year1='||"&year1"|| '&year2='||"&year2"|| ‘&debug=0'|| '&site='||trim(left(site_id))|| '"width="460" height="360">'; put link; put ']]>'; put '</description>'; …………………….

  18. County Coloring • Step 1: Prepare data for kml files. • Standard cleaning of data. • Determine variable for analysis. • Determine color scheme. • Data must include (county & state) fips and/or county name.

  19. County Coloring • Step 2: Perform any analyses required on data and determine levels for coloring counties. (i.e. Q1, median, Q3) • Assign levels to macro variables. Example: proc univariate data = USmap3 noprint;var dense; output out = USmap pctlpts=30 60 90 pctlpre=P;run;quit; data test; set USmap; call symput('first',P30); call symput('second',P60); call symput('third',P90); run;quit;

  20. County Coloring • Step 3: Create variable for each observation to hold hexadecimal color code. • Note: hexadecimal color codes are slightly different in Google Earth. The order is aabbggrr while standard web hexadecimal is rrggbb. • aa = alpha (00 to ff). For alpha, 00 is completely transparent and ff is completely opaque. • bb = blue (00 to ff) • gg = green (00 to ff) • rr = (00 to ff). • The range of any one color is from 0 to 255. A list of hexadecimal colors may be found online.

  21. County Coloring (Step 3 cont’d) Temporary datastep example: data temp; set mapdata3; length one 8 two 8 three 8; one = &first; two = &second; three = &third; if dense >= three then do; color = 'c0000000';end; *Top 10 percent color is black for all pollutants; if two <= dense < three then do; color = &color1;end; *60th-90th; if one <= dense < two then do; color = &color2;end; *30th-60th; if dense < one then do; color = &color3;end; *0-30th; run;quit;

  22. County Coloring • Step 4: Retrieve perimeter lat / long for each county. • Lat / long stored in SAS maps.counties • Lat / long stored in radians • Dataset includes (county & state) fips • Lat / long must be converted to degrees. • Lat / long must be ordered in counter-clockwise order for Google Earth to plot correctly.

  23. County Coloring • Step 5: Prepare perimeter lat / long coordinates. data county; set maps.counties; if state ^= &stfips then do; delete;end; if density > 4 then do; *remove high density for lower resolution map; delete;end; if segment > 1 then do; *remove multiple segments; delete;end; if x = ‘.’ OR y = ‘.’ then do; *remove missing data in maps.counties; delete;end; *Convert radian lat / long to degrees; pi = gamma(0.5)**2; long = x * -(180/pi); lat = y * (180/pi); elev = 3000; *preset elevation for kml plotting; run;quit;

  24. County Coloring • Step 6: Putting lat / long in counter-clockwise order. Sort both datasets (temp & county) by county fips then merge: data count; set merged; by county; if first.county then counter=0 and num = 0; counter+1; if last.county then num = counter; run;quit; proc sort data = count; by county_name descending counter; run;quit; data nums; set count; if num = '.' then do; delete; end; run;quit;

  25. County Coloring • Step 7 & 8: Prepare array’s and do statements for lat / long (Note: 2 counties & all of Alaska require a different method) This step involves a smaller section of code which writes the arrays to hold the lat / long. *write code to text file for arrays; data _null_; set nums; file ‘C:\Documents and Settings\user\Desktop\arrays.txt’;; ifname = 'if county_name = "'||trim(left(county_name))||'" then do;'; temp = lowcase(county_name); shrtname = substr(temp, 1, 8); cut = compress(shrtname,".","s"); arname = 'array lo'||trim(left(cut))||'('||trim(left(num))||') long1-long'||trim(left(num))||';'; arname2 = 'array lt'||trim(left(cut))||'('||trim(left(num))||') lat1-lat'||trim(left(num))||';'; ends = 'end;'; put ifname; put arname; put arname2; put ends; run;quit;

  26. County Coloring This section writes the do statements. data _null_; set nums; file 'C:\Documents and Settings\user\Desktop\dos.txt’; temp = lowcase(county_name); name = substr(temp, 1, 8); cut = compress(temp,".","s"); name2 = 'if county_name = "'||trim(left(county_name))||'" then do;'; dos = 'do i=1 to '||trim(left(num))||';'; cords = 'cord = trim(left(lo'||trim(left(cut))||'(i)))||'',''||trim(left(lt'||trim(left(cut))||'(i)))||'',3000 '';'; pcord = 'put cord;'; ends = 'end;end;'; put name2; put dos; put cords; put pcord; put ends; run;quit;

  27. County Coloring • Step 9: Prepare lat / long for storing in arrays and printing to kml file. proc transpose data = count out = count1 prefix = long; by county_name county_fips color; var long; run;quit; proc transpose data = count out = count2 prefix = lat; by county_name county_fips color; var lat; run;quit; data latlong; merge count1 count2; by county_name; run;quit;

  28. County Coloring • Step 10: Creating our county colored kml overlay. data _null_; set latlong end=last; file <fref>; If county_name = “” then do; delete;end; *Paste arrays written to text file here. Arrays must be defined and used in the same datastep. if _n_ = 1 then do; put '<?xml version="1.0" encoding="UTF-8"?>'; put '<kml xmlns="http://earth.google.com/kml/2.2">'; put '<Document>'; put '<name>Alabama</name>'; end; style = '<Style id=“exNAMEL'||trim(left(county_fips))||'">'; *This is a style reference specific to kml and does not necessarily need county fips; put style; put '<PolyStyle>'; col = '<color>'||trim(left(color))||'</color>'; put col; put '</PolyStyle>'; put '</Style>' ; put '<Placemark>'; put '<name>' county_name '</name>'; styleurl = '<styleUrl>#exNAME'||trim(left(county_fips))||'</styleUrl>'; *style ref call specific to kml; put styleurl; put '<Polygon>'; put '<altitudeMode>relativeToGround</altitudeMode>'; put '<outerBoundaryIs><LinearRing><coordinates>' ; *Paste do statements written to text file here. This will call on the arrays and write the lat / long to the kml file; put '</coordinates></LinearRing></outerBoundaryIs></Polygon>' ; put '</Placemark>'; if last then do; put '</Document>'; put ‘</kml>’; end; run;quit;

  29. Special Cases • There are a handful of special cases: • Denver, CO • Miami-Dade, FL • The state of Alaska • Maps.counties does not have perimeter coordinates for these cases. • Perimeters must be defined slightly different.

  30. Special Cases • Before creating the kml file a _null_ datastep must be performed to define the perimeters. Ex. Using Denver, CO: data _null_; set latlong; if county_name = "Denver" then do; initial = 8; call symput('denv0' , initial); call symput('denv1' , "-104.7337929,39.812544295,3000 -104.7876694,39.78331108500001,3000 -104.8649872,39.812544295,3000"); call symput('denv2' , "-104.9022527,39.783884821,3000 -104.9709917,39.80164331300001,3000 -105.0523529,39.790769652,3000 -105.0523529,39.66758036,3000"); call symput('denv3' , "-105.0769962,39.669301567,3000 -105.0620791,39.645805717,3000 -105.1245343,39.616572507,3000 -105.0523529,39.609714997,3000"); call symput('denv4' , "-105.0523529,39.613130092,3000 -105.0523529,39.622883602,3000 -105.0523529,39.624031074,3000 -105.0523529,39.627473489,3000"); call symput('denv5' , "-105.0523529,39.629194697,3000 -105.0523529,39.63148964,3000 -105.0277096,39.628047225,3000 -105.0334469,39.65323696200001,3000"); call symput('denv6' , "-105.0076561,39.678454021,3000 -105.0099511,39.660121793,3000 -104.9727402,39.66758036,3000 -104.8838931,39.624604809,3000"); call symput('denv7' , "-104.8793032,39.652663227,3000 -104.8472287,39.658974321,3000 -104.9027991,39.66758036,3000 -104.907389,39.683617644,3000"); call symput('denv8' , "-104.8649872,39.701949872,3000 -104.8838931,39.739761799,3000 -104.855261,39.768995008,3000 -104.7337929,39.768995008,3000");end; run;quit;

  31. Special Cases • After defining these macro variables in this fashion a simple do loop will insert these coordinates into the kml file. if county_name = "Denver" then do; %do i=1 %to &denv0; put "&&denv&i"; %end; end;

  32. How do we expect to benefit? Conclusions • Easier access to emissions information • Information in easy-to-use formats • Ability to answer more questions • Site easier to maintain • Efficient use of our data systems • Saves staff time and resources

  33. Questions?

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