Editing SimTX API/Packets/EphemerisResponse

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{{SimTX packet
| name = EphemerisResponse
| frame = ServerFrame
| field = 40
| member = ephemeris
| direction = s2c
| session = [[SimTX API/Control session|Control]]
| roles = <code>ROLE_CONTROL</code>.
| permission = None
| answers = [[SimTX API/Packets/EphemerisRequest|EphemerisRequest]]
| group = control
| file = control.proto
}}
'''EphemerisResponse''' returns the satellite positions requested by an [[SimTX API/Packets/EphemerisRequest|EphemerisRequest]]. Failures arrive as [[SimTX API/Packets/Error|Error]].

== Definition ==
<syntaxhighlight lang="protobuf">
message EphemerisResponse {
  reserved 4;
  int64 request_id = 1;
  bytes station_id = 2;
  repeated EphemerisSample samples = 3;
}
</syntaxhighlight>

== Fields ==
{| class="wikitable"
! # !! Field !! Type !! Description
|-
| 1 || <code>request_id</code> || <code>int64</code> || The request this answers.
|-
| 2 || <code>station_id</code> || <code>bytes</code> || The satellite.
|-
| 3 || <code>samples</code> || <code>repeated</code> [[#EphemerisSample|EphemerisSample]] || Samples from <code>from_ms</code> to <code>to_ms</code> every <code>step_seconds</code>.
|}

Field number 4 is reserved; do not use it.

=== EphemerisSample ===
<syntaxhighlight lang="protobuf">
message EphemerisSample {
  int64 t_ms = 1;
  double latitude_deg = 2;
  double longitude_deg = 3;
  double altitude_meters = 4;
  double x = 5;                // ECEF metres (6371 km sphere)
  double y = 6;
  double z = 7;
}
</syntaxhighlight>
{| class="wikitable"
! # !! Field !! Type !! Description
|-
| 1 || <code>t_ms</code> || <code>int64</code> || Sample time, Unix ms.
|-
| 2 || <code>latitude_deg</code> || <code>double</code> || Sub-satellite latitude, degrees.
|-
| 3 || <code>longitude_deg</code> || <code>double</code> || Sub-satellite longitude, degrees.
|-
| 4 || <code>altitude_meters</code> || <code>double</code> || Height above the 6,371 km sphere, metres.
|-
| 5 || <code>x</code> || <code>double</code> || Earth-fixed (ECEF) position, metres, on the 6,371 km sphere model.
|-
| 6 || <code>y</code> || <code>double</code> || ECEF y, metres.
|-
| 7 || <code>z</code> || <code>double</code> || ECEF z, metres.
|}

== Example ==
Complete frames, including the varint length prefix.

'''<code>ephemeris_response</code>''' (server to client, 152 bytes):

<syntaxhighlight lang="text">
96 01                           frame length 150
C2 02 92 01                     ephemeris (EphemerisResponse), 146 bytes
  08 15                         request_id = 21
  12 10 99 99 99 99 …           station_id = 99999999-8888-4777-8666-555555555555
  1A 3D                         samples (EphemerisSample), 61 bytes
    08 80 94 83 B9 97 34        t_ms = 1793000000000
    11 00 00 00 00 00 00 24 40  latitude_deg = 10.0
    19 00 00 00 00 00 00 34 40  longitude_deg = 20.0
    21 00 00 00 00 E0 C8 20 41  altitude_meters = 550000.0
    29 00 00 00 00 70 8D 56 41  x = 5912000.0
    31 00 00 00 00 2C 69 40 41  y = 2151000.0
    39 00 00 00 00 50 57 32 41  z = 1202000.0
  1A 3D                         samples (EphemerisSample), 61 bytes
    08 B0 FE 84 B9 97 34        t_ms = 1793000030000
    11 9A 99 99 99 99 99 27 40  latitude_deg = 11.8
    19 66 66 66 66 66 66 34 40  longitude_deg = 20.4
    21 00 00 00 00 A8 C9 20 41  altitude_meters = 550100.0
    29 00 00 00 00 E4 50 56 41  x = 5850000.0
    31 00 00 00 00 C0 7A 40 41  y = 2160000.0
    39 00 00 00 00 A8 60 35 41  z = 1401000.0
</syntaxhighlight>

== See also ==
* [[SimTX API/Packets/EphemerisRequest|EphemerisRequest]]
* [[SimTX API/Satellites]]

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