topic how to convert a longitude and latitude coordinates into geohash in SAS in SAS Programming

how to convert a longitude and latitude coordinates into geohash in SAS

Dublin187 — Wed, 06 Mar 2019 21:21:24 GMT

Hi,

I have a CSV file with a variable for longitude and another variable for latitude for over 20 000 observations.

I need to convert these coordinates into geohash by creating a new variable in SAS.

The end goal is to merge this data set with another one based with the identifier variable geohash.

Does anyone know how to do this?

Thank you in advance for your help

Re: how to convert a longitude and latitude coordinates into geohash in SAS

s_lassen — Thu, 07 Mar 2019 09:01:54 GMT

I could not find the routine for calculating geohashes. But you can get the result from geohash.org, e.g.:

data have; /* just som random test data */
  input latitude longitude;
cards;
45.63 114.67
18.876 11.44
;run;

filename geohash url;
data want;
  set have;
  fname=cats('http://geohash.org/?q=',latitude,',',longitude,'&format=url&redirect=0');
  infile geohash url filevar=fname truncover;
  input url $40.;  /* the result is like http://geohash.org/c216ne */
  geohash=scan(url,-1,'/');
run;

Re: how to convert a longitude and latitude coordinates into geohash in SAS

ChrisNZ — Thu, 07 Mar 2019 20:54:50 GMT

I replicated the logic shown in Wikipedia to transform a geohash into coordinates.

You can write the reverse operation.

You can do this in a macro or use proc fcmp to make it easier to call.

Does this help?

data _null_;
  GEOMAP_CHAR='ezs42';
  length GEOMAP_BIN LAT_BIN LON_BIN $50;
  do I=1 to length(GEOMAP_CHAR);
    VAL_DEC=index('0123456789bcdefghjkmnpqrstuvwxyz',char(GEOMAP_CHAR,I))-1;
    VAL_BIN=put(VAL_DEC,binary5.);     
    GEOMAP_BIN=catt(GEOMAP_BIN,VAL_BIN);      
  end;     
  do I=1 to length(GEOMAP_BIN);
    if mod(I,2)=0 then LAT_BIN=catt(LAT_BIN,char(GEOMAP_BIN,I));      
    else               LON_BIN=catt(LON_BIN,char(GEOMAP_BIN,I));      
  end;          
  do I=1 to length(LAT_BIN);
    SPAN=180/2**I;
    INC=ifn(char(LAT_BIN,I)='1',1,-1);
    LAT_INC=SPAN/2*INC;
    LAT+LAT_INC;       
  end;
  do I=1 to length(LON_BIN);
    SPAN=360/2**I;
    INC=ifn(char(LON_BIN,I)='1',1,-1);
    LON_INC=SPAN/2*INC;
    LON+LON_INC;       
  end;          
  putlog LAT= LON=;
run;

LAT=42.604980469 LON=-5.603027344

Re: how to convert a longitude and latitude coordinates into geohash in SAS

Dublin187 — Thu, 07 Mar 2019 21:07:50 GMT

Hi,

Thank you for your suggestion. I am only a beginner in coding so writing the reverse operation of this code would very challenging for me.

Can this translation program be applied for a longitude and latitude variables? or do I have to input the data individually?

Re: how to convert a longitude and latitude coordinates into geohash in SAS

ChrisNZ — Thu, 07 Mar 2019 22:04:04 GMT

This does the reverse translation:

data HAVE;
  LAT=42.604980469 ;
  LON=-5.603027344 ;
run;
data WANT;
  set HAVE;
  keep  GEOMAP_CHAR;
  GEOMAP_LEN=5;   
  length GEOMAP_CHAR $5 GEOMAP_BIN LAT_BIN LON_BIN $50;

  LOW=-180;
  do I=1 to ceil(GEOMAP_LEN*5/2+1);
    SPAN   = 360/2**I;  
    CENTER = LOW+SPAN; 
    INC    = (LON > CENTER);
    LOW    = LOW+SPAN*INC;               
    LON_BIN= catt(LON_BIN,INC);       
  end;          
  LOW=-90;
  do I=1 to ceil(GEOMAP_LEN*5/2);
    SPAN   = 180/2**I;  
    CENTER = LOW+SPAN; 
    INC    = (LAT > CENTER);
    LOW    = LOW+SPAN*INC;               
    LAT_BIN= catt(LAT_BIN,INC);       
  end;        
  do I=1 to ceil(GEOMAP_LEN*5/2);
    GEOMAP_BIN=catt(GEOMAP_BIN,char(LON_BIN,I));       
    GEOMAP_BIN=catt(GEOMAP_BIN,char(LAT_BIN,I));      
  end;          
  do I=1 to GEOMAP_LEN*5 by 5;  
    VAL_BIN=substr(GEOMAP_BIN,I,I+5);
    VAL_DEC=input(VAL_BIN,binary5.);
    VAL_CHAR=char('0123456789bcdefghjkmnpqrstuvwxyz',VAL_DEC+1); 
    GEOMAP_CHAR=catt(GEOMAP_CHAR,VAL_CHAR);
  end;
  putlog GEOMAP_CHAR=;
run;

GEOMAP_CHAR=ezs42