391 lines
10 KiB
C++
391 lines
10 KiB
C++
/*
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* Copyright 2013 Daniel Warner <contact@danrw.com>
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <Observer.h>
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#include <SGP4.h>
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#include <Util.h>
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#include <CoordTopocentric.h>
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#include <CoordGeodetic.h>
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#include <cmath>
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#include <iostream>
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#include <list>
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struct PassDetails
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{
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libsgp4::DateTime aos;
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libsgp4::DateTime los;
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double max_elevation;
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};
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double FindMaxElevation(
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const libsgp4::CoordGeodetic& user_geo,
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libsgp4::SGP4& sgp4,
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const libsgp4::DateTime& aos,
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const libsgp4::DateTime& los)
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{
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libsgp4::Observer obs(user_geo);
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bool running;
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double time_step = (los - aos).TotalSeconds() / 9.0;
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libsgp4::DateTime current_time(aos); //! current time
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libsgp4::DateTime time1(aos); //! start time of search period
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libsgp4::DateTime time2(los); //! end time of search period
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double max_elevation; //! max elevation
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running = true;
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do
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{
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running = true;
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max_elevation = -99999999999999.0;
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while (running && current_time < time2)
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{
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/*
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* find position
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*/
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libsgp4::Eci eci = sgp4.FindPosition(current_time);
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libsgp4::CoordTopocentric topo = obs.GetLookAngle(eci);
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if (topo.elevation > max_elevation)
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{
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/*
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* still going up
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*/
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max_elevation = topo.elevation;
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/*
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* move time along
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*/
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current_time = current_time.AddSeconds(time_step);
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if (current_time > time2)
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{
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/*
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* dont go past end time
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*/
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current_time = time2;
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}
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}
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else
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{
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/*
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* stop
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*/
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running = false;
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}
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}
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/*
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* make start time to 2 time steps back
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*/
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time1 = current_time.AddSeconds(-2.0 * time_step);
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/*
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* make end time to current time
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*/
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time2 = current_time;
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/*
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* current time to start time
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*/
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current_time = time1;
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/*
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* recalculate time step
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*/
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time_step = (time2 - time1).TotalSeconds() / 9.0;
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}
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while (time_step > 1.0);
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return max_elevation;
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}
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libsgp4::DateTime FindCrossingPoint(
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const libsgp4::CoordGeodetic& user_geo,
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libsgp4::SGP4& sgp4,
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const libsgp4::DateTime& initial_time1,
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const libsgp4::DateTime& initial_time2,
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bool finding_aos)
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{
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libsgp4::Observer obs(user_geo);
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bool running;
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int cnt;
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libsgp4::DateTime time1(initial_time1);
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libsgp4::DateTime time2(initial_time2);
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libsgp4::DateTime middle_time;
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running = true;
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cnt = 0;
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while (running && cnt++ < 16)
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{
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middle_time = time1.AddSeconds((time2 - time1).TotalSeconds() / 2.0);
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/*
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* calculate satellite position
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*/
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libsgp4::Eci eci = sgp4.FindPosition(middle_time);
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libsgp4::CoordTopocentric topo = obs.GetLookAngle(eci);
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if (topo.elevation > 0.0)
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{
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/*
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* satellite above horizon
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*/
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if (finding_aos)
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{
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time2 = middle_time;
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}
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else
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{
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time1 = middle_time;
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}
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}
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else
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{
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if (finding_aos)
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{
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time1 = middle_time;
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}
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else
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{
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time2 = middle_time;
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}
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}
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if ((time2 - time1).TotalSeconds() < 1.0)
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{
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/*
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* two times are within a second, stop
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*/
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running = false;
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/*
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* remove microseconds
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*/
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int us = middle_time.Microsecond();
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middle_time = middle_time.AddMicroseconds(-us);
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/*
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* step back into the pass by 1 second
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*/
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middle_time = middle_time.AddSeconds(finding_aos ? 1 : -1);
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}
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}
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/*
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* go back/forward 1second until below the horizon
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*/
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running = true;
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cnt = 0;
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while (running && cnt++ < 6)
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{
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libsgp4::Eci eci = sgp4.FindPosition(middle_time);
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libsgp4::CoordTopocentric topo = obs.GetLookAngle(eci);
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if (topo.elevation > 0)
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{
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middle_time = middle_time.AddSeconds(finding_aos ? -1 : 1);
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}
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else
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{
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running = false;
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}
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}
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return middle_time;
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}
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std::list<struct PassDetails> GeneratePassList(
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const libsgp4::CoordGeodetic& user_geo,
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libsgp4::SGP4& sgp4,
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const libsgp4::DateTime& start_time,
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const libsgp4::DateTime& end_time,
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const int time_step)
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{
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std::list<struct PassDetails> pass_list;
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libsgp4::Observer obs(user_geo);
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libsgp4::DateTime aos_time;
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libsgp4::DateTime los_time;
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bool found_aos = false;
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libsgp4::DateTime previous_time(start_time);
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libsgp4::DateTime current_time(start_time);
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while (current_time < end_time)
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{
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bool end_of_pass = false;
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/*
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* calculate satellite position
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*/
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libsgp4::Eci eci = sgp4.FindPosition(current_time);
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libsgp4::CoordTopocentric topo = obs.GetLookAngle(eci);
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if (!found_aos && topo.elevation > 0.0)
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{
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/*
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* aos hasnt occured yet, but the satellite is now above horizon
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* this must have occured within the last time_step
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*/
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if (start_time == current_time)
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{
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/*
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* satellite was already above the horizon at the start,
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* so use the start time
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*/
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aos_time = start_time;
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}
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else
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{
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/*
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* find the point at which the satellite crossed the horizon
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*/
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aos_time = FindCrossingPoint(
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user_geo,
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sgp4,
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previous_time,
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current_time,
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true);
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}
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found_aos = true;
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}
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else if (found_aos && topo.elevation < 0.0)
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{
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found_aos = false;
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/*
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* end of pass, so move along more than time_step
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*/
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end_of_pass = true;
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/*
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* already have the aos, but now the satellite is below the horizon,
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* so find the los
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*/
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los_time = FindCrossingPoint(
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user_geo,
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sgp4,
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previous_time,
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current_time,
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false);
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struct PassDetails pd;
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pd.aos = aos_time;
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pd.los = los_time;
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pd.max_elevation = FindMaxElevation(
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user_geo,
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sgp4,
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aos_time,
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los_time);
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pass_list.push_back(pd);
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}
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/*
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* save current time
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*/
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previous_time = current_time;
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if (end_of_pass)
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{
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/*
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* at the end of the pass move the time along by 30mins
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*/
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current_time = current_time + libsgp4::TimeSpan(0, 30, 0);
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}
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else
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{
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/*
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* move the time along by the time step value
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*/
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current_time = current_time + libsgp4::TimeSpan(0, 0, time_step);
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}
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if (current_time > end_time)
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{
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/*
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* dont go past end time
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*/
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current_time = end_time;
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}
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};
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if (found_aos)
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{
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/*
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* satellite still above horizon at end of search period, so use end
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* time as los
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*/
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struct PassDetails pd;
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pd.aos = aos_time;
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pd.los = end_time;
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pd.max_elevation = FindMaxElevation(user_geo, sgp4, aos_time, end_time);
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pass_list.push_back(pd);
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}
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return pass_list;
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}
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int main()
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{
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libsgp4::CoordGeodetic geo(51.507406923983446, -0.12773752212524414, 0.05);
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libsgp4::Tle tle("GALILEO-PFM (GSAT0101) ",
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"1 37846U 11060A 12293.53312491 .00000049 00000-0 00000-0 0 1435",
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"2 37846 54.7963 119.5777 0000994 319.0618 40.9779 1.70474628 6204");
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libsgp4::SGP4 sgp4(tle);
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std::cout << tle << std::endl;
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/*
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* generate 7 day schedule
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*/
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libsgp4::DateTime start_date = libsgp4::DateTime::Now(true);
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libsgp4::DateTime end_date(start_date.AddDays(7.0));
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std::list<struct PassDetails> pass_list;
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std::cout << "Start time: " << start_date << std::endl;
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std::cout << "End time : " << end_date << std::endl << std::endl;
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/*
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* generate passes
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*/
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pass_list = GeneratePassList(geo, sgp4, start_date, end_date, 180);
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if (pass_list.begin() == pass_list.end())
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{
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std::cout << "No passes found" << std::endl;
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}
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else
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{
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std::stringstream ss;
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ss << std::right << std::setprecision(1) << std::fixed;
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std::list<struct PassDetails>::const_iterator itr = pass_list.begin();
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do
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{
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ss << "AOS: " << itr->aos
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<< ", LOS: " << itr->los
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<< ", Max El: " << std::setw(4) << libsgp4::Util::RadiansToDegrees(itr->max_elevation)
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<< ", Duration: " << (itr->los - itr->aos)
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<< std::endl;
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}
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while (++itr != pass_list.end());
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std::cout << ss.str();
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}
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return 0;
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}
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