1 | #!/usr/bin/python |
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2 | #----------------------------------------------------------------------------- |
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3 | # Handles geometry on the earth's surface (e.g. bearing/distance) |
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4 | # |
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5 | # Usage: |
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6 | # (library code) |
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7 | #----------------------------------------------------------------------------- |
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8 | # Copyright 2007, Oliver White |
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9 | # |
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10 | # This program is free software: you can redistribute it and/or modify |
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11 | # it under the terms of the GNU General Public License as published by |
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12 | # the Free Software Foundation, either version 3 of the License, or |
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13 | # (at your option) any later version. |
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14 | # |
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15 | # This program is distributed in the hope that it will be useful, |
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16 | # but WITHOUT ANY WARRANTY; without even the implied warranty of |
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17 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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18 | # GNU General Public License for more details. |
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19 | # |
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20 | # You should have received a copy of the GNU General Public License |
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21 | # along with this program. If not, see <http://www.gnu.org/licenses/>. |
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22 | #----------------------------------------------------------------------------- |
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23 | from math import * |
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24 | from time import clock |
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25 | |
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26 | def bearing(a,b): |
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27 | dlat = radians(b[0] - a[0]) |
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28 | dlon = radians(b[1] - a[1]) |
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29 | |
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30 | dlon = dlon * cos(radians(a[0])) |
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31 | |
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32 | return(degrees(atan2(dlon, dlat))) |
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33 | |
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34 | def distance(a,b, haversine=False): |
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35 | if(haversine): |
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36 | return(distance_haversine(a,b)) |
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37 | lat1 = radians(a[0]) |
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38 | lon1 = radians(a[1]) |
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39 | lat2 = radians(b[0]) |
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40 | lon2 = radians(b[1]) |
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41 | d = acos(sin(lat1)*sin(lat2) + cos(lat1)*cos(lat2) * cos(lon2-lon1)) * 6371; |
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42 | return(d) |
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43 | |
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44 | |
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45 | def distance_haversine(a,b): |
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46 | dlat = radians(b[0] - a[0]) |
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47 | dlon = radians(b[1] - a[1]) |
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48 | a1 = sin(0.5 * dlat) |
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49 | a2a = cos(radians(a[0])) |
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50 | a2b = cos(radians(b[0])) |
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51 | a3 = sin(0.5 * dlon) |
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52 | |
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53 | a = a1*a1 + a2a*a2b * a3*a3 |
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54 | c = 2 * atan2(sqrt(a), sqrt(1-a)) |
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55 | d = 6371 * c |
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56 | return(d) |
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57 | |
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58 | def compassPoint(x): |
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59 | points = ('N','NNE','NE','ENE','E','ESE','SE','SSE','S','SSW','SW','WSW','W','WNW','NW','NNW') |
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60 | part = 360.0 / len(points) |
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61 | x = x + 0.5 * part |
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62 | while(x < 0): |
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63 | x = x + 360 |
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64 | while(x > 360): |
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65 | x = x - 360 |
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66 | point = int(x / part) |
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67 | return(points[point]) |
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68 | |
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69 | if(__name__ == "__main__"): |
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70 | if(0): |
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71 | # Test compass-point names |
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72 | x = -180 |
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73 | while(x < 360): |
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74 | print "%05.1f: %s" % (x, compassPoint(x)) |
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75 | x = x + 15 |
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76 | |
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77 | a = (51.478,-0.4856) |
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78 | b = (51.477,-0.4328) |
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79 | |
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80 | print bearing(a,b) |
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81 | |
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82 | for h in (True,False): |
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83 | start = clock() |
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84 | it = 5000 |
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85 | for i in range(it): |
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86 | d = distance(a,b,h) |
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87 | t = 1000*(clock() - start) / it |
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88 | print "%s: %1.3fms / iteration, gives %f" % (h and "haversine" or "normal", t, d) |
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