Distance and Bearing
You are encouraged to solve this task according to the task description, using any language you may know.
It is very important in aviation to have knowledge of the nearby airports at any time in flight.
- Task
Determine the distance and bearing from an Airplane to the 20 nearest Airports whenever requested. Use the non-commercial data from openflights.org airports.dat as reference.
A request comes from an airplane at position ( latitude, longitude ): ( 51.514669, 2.198581 ).
Your report should contain the following information from table airports.dat (column shown in brackets):
Name(2), Country(4), ICAO(6), Distance and Bearing calculated from Latitude(7) and Longitude(8).
Distance is measured in nautical miles (NM). Resolution is 0.1 NM.
Bearing is measured in degrees (°). 0° = 360° = north then clockwise 90° = east, 180° = south, 270° = west. Resolution is 1°.
- See
-
- openflights.org/data: Airport, airline and route data
- Movable Type Scripts: Calculate distance, bearing and more between Latitude/Longitude points
J
Implementation:
DAT=: {{ require'web/gethttp csv'
if.0=#$fread F=.'airports.dat' do.
(gethttp y) fwrite F
end.
readcsv F
}}'https://raw.githubusercontent.com/jpatokal/openflights/master/data/airports.dat'
LATLONG=: _".&>6 7{"1 DAT
fmtm=: {{
9!:7]9 1 1#' -'
r=._1 _1}.1 1}.":boxopen y
~.r[9!:7]9 1 1#'+|-'
}}
AIRPORTS=: 1 3 5{"1 DAT
deg=: %&180p_1 NB. convert from degrees
R=: 21600 % 2p1 NB. radius of spherical earth in nautical miles
dist=: {{R*2*_1 o.1<.%:(*:1 o.0.5*x-y)p.x*&(2 o.{.)y}}°
bear=: {{
re=. (2 o.{.y)*1 o.dlon=.y-&{:x
2p1|1r2p1-{:*.re j. ((*|.)/+.^j.x,&{.y) p.-2 o.dlon
}}&.deg
pkg=: {{ <"0 (<.0.5+x*y)%x }}
LABELS=: ;:'Airport Country ICAO Distance Bearing'
nearest=: {{
o=. 20{./: d=. y dist"1 LATLONG
fmtm LABELS,(o{AIRPORTS),"1 (10 pkg o{d),.1 pkg y bear"1 o{LATLONG
}}
For this task, we assume that the earth is a sphere rather than an oblate ellipsoid. Also, we report the initial bearing (at the requested location). For the task example, these issues are irrelevant, but they might become significant if code from this implementation was used in other contexts.
Task example:
nearest 51.514669 2.198581 Airport Country ICAO Distance Bearing ----------------------------------- -------------- ---- -------- ------- Koksijde Air Base Belgium EBFN 30.6 146 Ostend-Bruges International Airport Belgium EBOS 31.3 127 Kent International Airport United Kingdom EGMH 33.5 252 Calais-Dunkerque Airport France LFAC 34.4 196 Westkapelle heliport Belgium EBKW 42.5 105 Lympne Airport United Kingdom EGMK 51.6 240 Ursel Air Base Belgium EBUL 52.8 114 Southend Airport United Kingdom EGMC 56.2 274 Merville-Calonne Airport France LFQT 56.3 163 Wevelgem Airport Belgium EBKT 56.4 137 Midden-Zeeland Airport Netherlands EHMZ 57.2 90 Lydd Airport United Kingdom EGMD 58 235 RAF Wattisham United Kingdom EGUW 58.9 309 Beccles Airport United Kingdom EGSM 59.3 339 Lille/Marcq-en-Baroeul Airport France LFQO 59.6 146 Lashenden (Headcorn) Airfield United Kingdom EGKH 62.2 250 Le Touquet-Côte d'Opale Airport France LFAT 63.7 200 Rochester Airport United Kingdom EGTO 64.2 262 Lille-Lesquin Airport France LFQQ 66.2 149 Thurrock Airfield United Kingdom EGMT 68.4 272
Julia
using DataFrames
using CSV
const EARTH_RADIUS_KM = 6372.8
const TASK_CONVERT_NM = 0.0094174
const AIRPORT_DATA_FILE = "airports.dat.txt"
const QUERY = (latitude = 51.514669, longitude = 2.198581)
"""
Given two latitude, longitude pairs in degrees for two points on the Earth,
get distance (nautical miles) and initial direction of travel (degrees)
for travel from lat1, lon1 to lat2, lon2
"""
function haversine(lat1, lon1, lat2, lon2)
dlat = lat2 - lat1
dlon = lon2 - lon1
a = sind(dlat / 2)^2 + cosd(lat1) * cosd(lat2) * sind(dlon / 2)^2
c = 2.0 * asind(sqrt(a))
theta = atand(sind(dlon) * cosd(lat2),
cosd(lat1) * sind(lat2) - sind(lat1) * cosd(lat2) * cosd(dlon))
theta = (theta + 360) % 360
return EARTH_RADIUS_KM * c * TASK_CONVERT_NM, theta
end
""" Given latitude and longitude, find `wanted` closest airports in database file csv. """
function find_nearest_airports(latitude, longitude, wanted = 20, csv = AIRPORT_DATA_FILE)
airports = DataFrame(CSV.File(csv))[:, [2, 4, 6, 7, 8]]
airports[!, "d"] .= 0.0
airports[!, "b"] .= 0
rename!(airports, [:Name, :Country, :ICAO, :Latitude_deg, :Longitude_deg, :Distance, :Bearing])
for r in eachrow(airports)
distance, bearing = haversine(latitude, longitude, r.Latitude_deg, r.Longitude_deg)
r.Distance, r.Bearing = round(distance, digits = 1), Int(round(bearing))
end
sort!(airports, :Distance)
return airports[1:wanted, [:Name, :Country, :ICAO, :Distance, :Bearing]]
end
println(find_nearest_airports(QUERY.latitude, QUERY.longitude))
- Output:
20×5 DataFrame Row │ Name Country ICAO Distance Bearing │ String String String7 Float64 Int64 ─────┼─────────────────────────────────────────────────────────────────────────────── 1 │ Koksijde Air Base Belgium EBFN 30.6 146 2 │ Ostend-Bruges International Airp… Belgium EBOS 31.3 127 3 │ Kent International Airport United Kingdom EGMH 33.5 252 4 │ Calais-Dunkerque Airport France LFAC 34.4 196 5 │ Westkapelle heliport Belgium EBKW 42.6 105 6 │ Lympne Airport United Kingdom EGMK 51.6 240 7 │ Ursel Air Base Belgium EBUL 52.8 114 8 │ Southend Airport United Kingdom EGMC 56.2 274 9 │ Merville-Calonne Airport France LFQT 56.3 163 10 │ Wevelgem Airport Belgium EBKT 56.4 137 11 │ Midden-Zeeland Airport Netherlands EHMZ 57.2 90 12 │ Lydd Airport United Kingdom EGMD 58.0 235 13 │ RAF Wattisham United Kingdom EGUW 59.0 309 14 │ Beccles Airport United Kingdom EGSM 59.3 339 15 │ Lille/Marcq-en-Baroeul Airport France LFQO 59.7 146 16 │ Lashenden (Headcorn) Airfield United Kingdom EGKH 62.2 250 17 │ Le Touquet-Côte d'Opale Airport France LFAT 63.7 200 18 │ Rochester Airport United Kingdom EGTO 64.2 262 19 │ Lille-Lesquin Airport France LFQQ 66.2 149 20 │ Thurrock Airfield United Kingdom EGMT 68.4 272
PARI/GP
/* copy CSV aiports.dat from URL */
csv=externstr("curl 'https://raw.githubusercontent.com/jpatokal/openflights/master/data/airports.dat'");
/* We want an easy convert from CSV to matrix. */
/* Get rid of all those backslash in airports.dat */
{
for(i = 1 , #csv, tmp = Vecsmall(csv[i]);
for(j = 1 , #tmp, if(tmp[j]==92, tmp[j]=78));
csv[i] = strchr(tmp)
);
};
{
convert(csv,mat)=
write1(mat,"[");
for(i=1, #csv-1,
write1(mat,csv[i]); write1(mat,";")
);
write1(mat,csv[#csv]); write(mat,"]")
};
convert(csv,airports);
M = read(airports);
{
distance(lat1, lon1, lat2, lon2, unit = "mi") =
my(dist = 0, rlat1, rlat2, rtheta);
if(lat1!=lat2 || lon1!=lon2,
rlat1 = lat1*Pi/180; rlat2 = lat2*Pi/180;
rtheta = (lon1-lon2)*Pi/180;
dist = sin(rlat1)*sin(rlat2) + cos(rlat1)*cos(rlat2)*cos(rtheta);
dist = acos(min(dist,1))*180/Pi*60*1.1515576;
if(unit=="Km", dist*= 1.609344, unit=="NM", dist*= 0.868976)
);dist
};
{
bearing(lat1, lon1, lat2, lon2)=
my(bear, rlat1, rlat2, rdlon, x, y);
if (lat1!=lat2 || lon1!=lon2,
rlat1 = lat1*Pi/180; rlat2 = lat2*Pi/180;
rdlon = (lon2-lon1)*Pi/180;
y = sin(rdlon)*cos(rlat2);
x = cos(rlat1)*sin(rlat2) - sin(rlat1)*cos(rlat2)*cos(rdlon);
/* Pari/GP is developed for 30 years without built-in atan2() function, very unfortunate. */
if( x>0, bear=atan(y/x), x<0 && y>0, bear=atan(y/x)+Pi,
x<0 && y==0, bear=Pi, x<0 && y<0, bear=atan(y/x)-Pi,
x==0 && y>0, bear=Pi/2, x==0 && y<0, bear=-Pi/2);
bear = (bear*180/Pi+360)%360;
);bear
};
{
request(lat, lon, r = 20 , unit = "NM")=
my(D = vector(#M[,1]), R = matrix(r+1, 5));
R[1,1] = "NAME"; R[1,2] = "COUNTRY"; R[1,3] = "ICAO"; R[1,4] = "DISTANCE"; R[1,5] = "BEARING";
printf("%-36s%-18s\t%-5s\t%s\t%s\n", R[1,1], R[1,2], R[1,3], R[1,4], R[1,5]);
for(i = 1, #M[,1],
D[i] = [distance(lat, lon, M[i,7], M[i,8], unit) , i];
);
D=vecsort(D);
for(i = 1, r,
R[i+1,1] = M[D[i][2],2]; R[i+1,2] = M[D[i][2],4]; R[i+1,3] = M[D[i][2],6];
R[i+1,4] = D[i][1]; R[i+1,5] = bearing(lat, lon, M[D[i][2],7], M[D[i][2],8]);
printf("%-36s%-18s\t%-5s\t%.1f\t\t%.0f\n", R[i+1,1], R[i+1,2], R[i+1,3], R[i+1,4], R[i+1,5]);
);
}
request(51.514669, 2.198581)
- Output:
NAME COUNTRY ICAO DISTANCE BEARING Koksijde Air Base Belgium EBFN 30.7 146 Ostend-Bruges International Airport Belgium EBOS 31.3 127 Kent International Airport United Kingdom EGMH 33.5 252 Calais-Dunkerque Airport France LFAC 34.4 196 Westkapelle heliport Belgium EBKW 42.6 105 Lympne Airport United Kingdom EGMK 51.6 240 Ursel Air Base Belgium EBUL 52.8 114 Southend Airport United Kingdom EGMC 56.2 274 Merville-Calonne Airport France LFQT 56.4 163 Wevelgem Airport Belgium EBKT 56.5 137 Midden-Zeeland Airport Netherlands EHMZ 57.3 90 Lydd Airport United Kingdom EGMD 58.0 235 RAF Wattisham United Kingdom EGUW 59.0 309 Beccles Airport United Kingdom EGSM 59.3 339 Lille/Marcq-en-Baroeul Airport France LFQO 59.7 146 Lashenden (Headcorn) Airfield United Kingdom EGKH 62.2 250 Le Touquet-Côte d'Opale Airport France LFAT 63.7 200 Rochester Airport United Kingdom EGTO 64.2 262 Lille-Lesquin Airport France LFQQ 66.2 149 Thurrock Airfield United Kingdom EGMT 68.4 272 cpu time = 183 ms, real time = 183 ms.
Phix
without js -- file i/o enum Airport_ID, Name, City, Country, IATA, ICAO, Latitude, Longitude, Altitude, Timezone, DST, Tz_Olson, Type, Source function tabulate(sequence s) s = split(trim(s),"\n") for i,ri in s do ri = split(ri,',') if length(ri)!=14 then ri[2] &= ","&ri[3] ri[3..3] = {} end if for j in {Airport_ID, Latitude, Longitude, Altitude} do ri[j] = to_number(ri[j]) end for for j in {Name,City,Country,ICAO} do ri[j] = trim(ri[j],`"`) end for s[i] = ri end for return s end function constant airports = tabulate(get_text("airports.dat")) function distance(atom lat1, lon1, lat2, lon2, integer units) atom dist = 0 if lat1!=lat2 or lon1!=lon2 then atom radlat1 = lat1*PI/180, radlat2 = lat2*PI/180, radtheta = (lon1-lon2)*PI/180 dist = sin(radlat1)*sin(radlat2) + cos(radlat1)*cos(radlat2)*cos(radtheta) dist = arccos(min(dist,1))*180/PI * 60*1.1515576 -- in Statute Miles if units = 'K' then dist *= 1.609344 end if -- in Kilometres if units = 'N' then dist *= 0.868976 end if -- in Nautical Miles end if return dist end function function bearing(atom lat1, lon1, lat2, lon2) atom bear = NULL if lat1!=lat2 or lon1!=lon2 then atom radlat1 = lat1*PI/180, radlat2 = lat2*PI/180, raddlon = (lon2-lon1)*PI/180, y = sin(raddlon)*cos(radlat2), x = cos(radlat1)*sin(radlat2) - sin(radlat1)*cos(radlat2)*cos(raddlon) bear = remainder(atan2(y, x)*180/PI+360,360) end if return bear; end function procedure query(atom lat,lon, integer rows=20) sequence r = {} for a in airports do atom lat2 = a[Latitude], lon2 = a[Longitude], dist = round(distance(lat,lon,lat2,lon2,'N'),10), bear = round(bearing(lat,lon,lat2,lon2)) r = append(r,{a[Name],a[Country],a[ICAO],dist,bear}) end for r = sort_columns(r,{4})[1..rows] printf(1," Name | Country | ICAO | Distance in NM | Bearing in ° \n") printf(1,"-------------------------------------+----------------+------+----------------+--------------\n") printf(1,"%s\n",{join(r,"\n",fmt:=" %-36s| %-15s| %4s | %4.1f | %3d")}) printf(1,"(%d rows)\n",rows) end procedure query(51.514669, 2.198581)
- Output:
Name | Country | ICAO | Distance in NM | Bearing in ° -------------------------------------+----------------+------+----------------+-------------- Koksijde Air Base | Belgium | EBFN | 30.7 | 146 Ostend-Bruges International Airport | Belgium | EBOS | 31.3 | 127 Kent International Airport | United Kingdom | EGMH | 33.5 | 252 Calais-Dunkerque Airport | France | LFAC | 34.4 | 196 Westkapelle heliport | Belgium | EBKW | 42.6 | 105 Lympne Airport | United Kingdom | EGMK | 51.6 | 240 Ursel Air Base | Belgium | EBUL | 52.8 | 114 Southend Airport | United Kingdom | EGMC | 56.2 | 274 Merville-Calonne Airport | France | LFQT | 56.4 | 163 Wevelgem Airport | Belgium | EBKT | 56.5 | 137 Midden-Zeeland Airport | Netherlands | EHMZ | 57.3 | 90 Lydd Airport | United Kingdom | EGMD | 58.0 | 235 RAF Wattisham | United Kingdom | EGUW | 59.0 | 309 Beccles Airport | United Kingdom | EGSM | 59.3 | 339 Lille/Marcq-en-Baroeul Airport | France | LFQO | 59.7 | 146 Lashenden (Headcorn) Airfield | United Kingdom | EGKH | 62.2 | 250 Le Touquet-Côte d'Opale Airport | France | LFAT | 63.7 | 200 Rochester Airport | United Kingdom | EGTO | 64.2 | 262 Lille-Lesquin Airport | France | LFQQ | 66.2 | 149 Thurrock Airfield | United Kingdom | EGMT | 68.4 | 272 (20 rows)
Python
''' Rosetta Code task Distance_and_Bearing '''
from math import radians, degrees, sin, cos, asin, atan2, sqrt
from pandas import read_csv
EARTH_RADIUS_KM = 6372.8
TASK_CONVERT_NM = 0.0094174
AIRPORT_DATA_FILE = "../julia programs/airports.dat.txt"
QUERY_LATITUDE, QUERY_LONGITUDE = 51.514669, 2.198581
def haversine(lat1, lon1, lat2, lon2):
'''
Given two latitude, longitude pairs in degrees for two points on the Earth,
get distance (nautical miles) and initial direction of travel (degrees)
for travel from lat1, lon1 to lat2, lon2
'''
rlat1, rlon1, rlat2, rlon2 = [radians(x) for x in [lat1, lon1, lat2, lon2]]
dlat = rlat2 - rlat1
dlon = rlon2 - rlon1
arc = sin(dlat / 2) ** 2 + cos(rlat1) * cos(rlat2) * sin(dlon / 2) ** 2
clen = 2.0 * degrees(asin(sqrt(arc)))
theta = atan2(sin(dlon) * cos(rlat2),
cos(rlat1) * sin(rlat2) - sin(rlat1) * cos(rlat2) * cos(dlon))
theta = (degrees(theta) + 360) % 360
return EARTH_RADIUS_KM * clen * TASK_CONVERT_NM, theta
def find_nearest_airports(latitude, longitude, wanted=20, csv=AIRPORT_DATA_FILE):
''' Given latitude and longitude, find `wanted` closest airports in database file csv. '''
airports = read_csv(csv, header=None, usecols=[1, 3, 5, 6, 7], names=[
'Name', 'Country', 'ICAO', 'Latitude', 'Longitude'])
airports['Distance'] = 0.0
airports['Bearing'] = 0
for (idx, row) in enumerate(airports.itertuples()):
distance, bearing = haversine(
latitude, longitude, row.Latitude, row.Longitude)
airports.at[idx, 'Distance'] = round(distance, ndigits=1)
airports.at[idx, 'Bearing'] = int(round(bearing))
airports.sort_values(by=['Distance'], ignore_index=True, inplace=True)
return airports.loc[0:wanted-1, ['Name', 'Country', 'ICAO', 'Distance', 'Bearing']]
print(find_nearest_airports(QUERY_LATITUDE, QUERY_LONGITUDE))
- Output:
Name Country ICAO Distance Bearing 0 Koksijde Air Base Belgium EBFN 30.7 146 1 Ostend-Bruges International Airport Belgium EBOS 31.3 127 2 Kent International Airport United Kingdom EGMH 33.5 252 3 Calais-Dunkerque Airport France LFAC 34.4 196 4 Westkapelle heliport Belgium EBKW 42.6 105 5 Lympne Airport United Kingdom EGMK 51.6 240 6 Ursel Air Base Belgium EBUL 52.8 114 7 Southend Airport United Kingdom EGMC 56.2 274 8 Merville-Calonne Airport France LFQT 56.4 163 9 Wevelgem Airport Belgium EBKT 56.5 137 10 Midden-Zeeland Airport Netherlands EHMZ 57.3 90 11 Lydd Airport United Kingdom EGMD 58.0 235 12 RAF Wattisham United Kingdom EGUW 59.0 309 13 Beccles Airport United Kingdom EGSM 59.3 339 14 Lille/Marcq-en-Baroeul Airport France LFQO 59.7 146 15 Lashenden (Headcorn) Airfield United Kingdom EGKH 62.2 250 16 Le Touquet-Côte d'Opale Airport France LFAT 63.7 200 17 Rochester Airport United Kingdom EGTO 64.2 262 18 Lille-Lesquin Airport France LFQQ 66.2 149 19 Thurrock Airfield United Kingdom EGMT 68.4 272
SQL/PostgreSQL
Create table and copy from URL.
-- create table airports with 14 columns
CREATE TABLE airports (
Airport_ID serial PRIMARY KEY,
Name VARCHAR NOT NULL,
City VARCHAR,
Country VARCHAR NOT NULL,
IATA VARCHAR,
ICAO VARCHAR,
Latitude double precision NOT NULL,
Longitude double precision NOT NULL,
Altitude SMALLINT,
Timezone VARCHAR,
DST VARCHAR,
Tz_Olson VARCHAR,
Type VARCHAR,
Source VARCHAR
);
-- copy CSV airports.dat from URL
COPY airports FROM
PROGRAM 'curl "https://raw.githubusercontent.com/jpatokal/openflights/master/data/airports.dat"'
WITH (FORMAT csv);
Functions for distance and bearing.
-- calculate distance
CREATE OR REPLACE FUNCTION calculate_distance(lat1 float, lon1 float, lat2 float, lon2 float, units varchar)
RETURNS numeric AS $dist$
DECLARE
dist float = 0;
radlat1 float;
radlat2 float;
theta float;
radtheta float;
BEGIN
IF lat1 = lat2 AND lon1 = lon2
THEN RETURN dist;
ELSE
radlat1 = pi() * lat1 / 180;
radlat2 = pi() * lat2 / 180;
theta = lon1 - lon2;
radtheta = pi() * theta / 180;
dist = sin(radlat1) * sin(radlat2) + cos(radlat1) * cos(radlat2) * cos(radtheta);
IF dist > 1 THEN dist = 1; END IF;
dist = acos(dist);
dist = dist * 180 / pi();
-- Distance in Statute Miles
dist = dist * 60 * 1.1515576;
-- Distance in Kilometres
IF units = 'K' THEN dist = dist * 1.609344; END IF;
-- Distance in Nautical Miles
IF units = 'N' THEN dist = dist * 0.868976; END IF;
dist = dist::numeric;
RETURN dist;
END IF;
END;
$dist$ LANGUAGE plpgsql;
-- calculate bearing
CREATE OR REPLACE FUNCTION calculate_bearing(lat1 float, lon1 float, lat2 float, lon2 float)
RETURNS numeric AS $bear$
DECLARE
bear float = NULL;
radlat1 float;
radlat2 float;
raddlon float;
y float;
x float;
BEGIN
IF lat1 = lat2 AND lon1 = lon2
THEN RETURN bear;
ELSE
radlat1 = pi() * lat1 / 180;
radlat2 = pi() * lat2 / 180;
raddlon = pi() * (lon2 - lon1) / 180;
y = sin(raddlon) * cos(radlat2);
x = cos(radlat1) * sin(radlat2) - sin(radlat1) * cos(radlat2) * cos(raddlon);
bear = atan2(y, x) * 180 / pi();
bear = (bear::numeric + 360) % 360;
RETURN bear;
END IF;
END;
$bear$ LANGUAGE plpgsql;
Request from airplane at position ( 51.514669, 2.198581 ).
Select
Name "Name",
Country "Country",
ICAO "ICAO",
ROUND(calculate_distance(51.514669, 2.198581, Latitude, Longitude, 'N'), 1) "Distance in NM",
ROUND(calculate_bearing(51.514669, 2.198581, Latitude, Longitude), 0) "Bearing in °"
From
airports
ORDER BY "Distance in NM"
LIMIT 20;
- Output:
Name | Country | ICAO | Distance in NM | Bearing in ° -------------------------------------+----------------+------+----------------+-------------- Koksijde Air Base | Belgium | EBFN | 30.7 | 146 Ostend-Bruges International Airport | Belgium | EBOS | 31.3 | 127 Kent International Airport | United Kingdom | EGMH | 33.5 | 252 Calais-Dunkerque Airport | France | LFAC | 34.4 | 196 Westkapelle heliport | Belgium | EBKW | 42.6 | 105 Lympne Airport | United Kingdom | EGMK | 51.6 | 240 Ursel Air Base | Belgium | EBUL | 52.8 | 114 Southend Airport | United Kingdom | EGMC | 56.2 | 274 Merville-Calonne Airport | France | LFQT | 56.4 | 163 Wevelgem Airport | Belgium | EBKT | 56.5 | 137 Midden-Zeeland Airport | Netherlands | EHMZ | 57.3 | 90 Lydd Airport | United Kingdom | EGMD | 58.0 | 235 RAF Wattisham | United Kingdom | EGUW | 59.0 | 309 Beccles Airport | United Kingdom | EGSM | 59.3 | 339 Lille/Marcq-en-Baroeul Airport | France | LFQO | 59.7 | 146 Lashenden (Headcorn) Airfield | United Kingdom | EGKH | 62.2 | 250 Le Touquet-Côte d'Opale Airport | France | LFAT | 63.7 | 200 Rochester Airport | United Kingdom | EGTO | 64.2 | 262 Lille-Lesquin Airport | France | LFQQ | 66.2 | 149 Thurrock Airfield | United Kingdom | EGMT | 68.4 | 272 (20 rows)
Wren
However, rather than use Wren-sql, we program it so that it can be run from Wren-CLI. Runtime is about 0.24 seconds.
import "io" for File
import "./dynamic" for Tuple
import "./fmt" for Fmt
var airportFields = [
"airportID",
"name",
"city",
"country",
"iata",
"icao",
"latitude",
"longitude",
"altitude",
"timezone",
"dst",
"tzOlson",
"type",
"source"
]
var Airport = Tuple.create("Airport", airportFields)
var fileName = "airports.dat" // local copy
var lines = File.read(fileName).trimEnd().split("\n")
var lc = lines.count
var airports = List.filled(lc, null)
for (i in 0...lc) {
var fields = lines[i].split(",").map { |f| f.replace("\"", "") }.toList
if (fields.count == 15) { // airport name has an embedded comma
fields[1] = fields[1] + "," + fields[2]
for (i in 2..13) fields[i] = fields[i+1]
}
var airportID = Num.fromString(fields[0])
var name = fields[1]
var city = fields[2]
var country = fields[3]
var iata = fields[4]
var icao = fields[5]
var latitude = Num.fromString(fields[6])
var longitude = Num.fromString(fields[7])
var altitude = Num.fromString(fields[8])
var timezone = fields[9]
var dst = fields[10]
var tzOlson = fields[11]
var type = fields[12]
var source = fields[13]
airports[i] = Airport.new(airportID, name, city, country, iata, icao, latitude, longitude,
altitude, timezone, dst, tzOlson, type, source)
}
var calculateDistance = Fn.new { |lat1, lon1, lat2, lon2, units|
if (lat1 == lat2 && lon1 == lon2) return 0
var radlat1 = Num.pi * lat1 / 180
var radlat2 = Num.pi * lat2 / 180
var theta = lon1 - lon2
var radtheta = Num.pi * theta / 180
var dist = radlat1.sin * radlat2.sin + radlat1.cos * radlat2.cos * radtheta.cos
if (dist > 1) dist = 1
dist = dist.acos * 180 / Num.pi * 60 * 1.1515576 // distance in statute miles
if (units == "K") dist = dist * 1.609344 // distance in kilometers
if (units == "N") dist = dist * 0.868976 // distance in nautical miles
return dist
}
var calculateBearing = Fn.new { |lat1, lon1, lat2, lon2|
if (lat1 == lat2 && lon1 == lon2) return 0
var radlat1 = Num.pi * lat1 / 180
var radlat2 = Num.pi * lat2 / 180
var raddlon = Num.pi * (lon2 - lon1) / 180
var y = raddlon.sin * radlat2.cos
var x = radlat1.cos * radlat2.sin - radlat1.sin * radlat2.cos * raddlon.cos
var bear = y.atan(x) * 180 / Num.pi
return (bear + 360) % 360
}
// request from airplane at position (51.514669, 2.198581)
var query = List.filled(airports.count, null)
for (i in 0...airports.count) {
var a = airports[i]
var dist = calculateDistance.call(51.514669, 2.198581, a.latitude, a.longitude, "N")
dist = (dist * 10).round / 10
var bear = calculateBearing.call(51.514669, 2.198581, a.latitude, a.longitude).round
query[i] = [a.name, a.country, a.icao, dist, bear]
}
query.sort { |q1, q2| q1[3] < q2[3] }
System.print(" Name | Country | ICAO | Distance in NM | Bearing in ° ")
System.print("-------------------------------------+----------------+------+----------------+--------------")
var fmt = " $-36s| $-15s| $4s | $4.1f | $3d"
for (i in 0..19) Fmt.lprint(fmt, query[i])
System.print("(20 rows)")
- Output:
Name | Country | ICAO | Distance in NM | Bearing in ° -------------------------------------+----------------+------+----------------+-------------- Koksijde Air Base | Belgium | EBFN | 30.7 | 146 Ostend-Bruges International Airport | Belgium | EBOS | 31.3 | 127 Kent International Airport | United Kingdom | EGMH | 33.5 | 252 Calais-Dunkerque Airport | France | LFAC | 34.4 | 196 Westkapelle heliport | Belgium | EBKW | 42.6 | 105 Lympne Airport | United Kingdom | EGMK | 51.6 | 240 Ursel Air Base | Belgium | EBUL | 52.8 | 114 Southend Airport | United Kingdom | EGMC | 56.2 | 274 Merville-Calonne Airport | France | LFQT | 56.4 | 163 Wevelgem Airport | Belgium | EBKT | 56.5 | 137 Midden-Zeeland Airport | Netherlands | EHMZ | 57.3 | 90 Lydd Airport | United Kingdom | EGMD | 58.0 | 235 RAF Wattisham | United Kingdom | EGUW | 59.0 | 309 Beccles Airport | United Kingdom | EGSM | 59.3 | 339 Lille/Marcq-en-Baroeul Airport | France | LFQO | 59.7 | 146 Lashenden (Headcorn) Airfield | United Kingdom | EGKH | 62.2 | 250 Le Touquet-Côte d'Opale Airport | France | LFAT | 63.7 | 200 Rochester Airport | United Kingdom | EGTO | 64.2 | 262 Lille-Lesquin Airport | France | LFQQ | 66.2 | 149 Thurrock Airfield | United Kingdom | EGMT | 68.4 | 272