randy
61ba86c6e6
bin/gnss_simulator.rb speaks gpsd's own JSON wire protocol directly on its default port -- GpsdClient connects to it exactly as it would to real gpsd, no app changes needed, and no gpsd install/daemon required either (unlike the existing fake-NMEA-source approach in docs/development.adoc, which still needs gpsd itself in front of it). Drives a loop around a center point at a driving-ish pace rather than sitting still, since a fixed position isn't much of a "GNSS position" to look at. Verified end to end: started it, pointed a dev server at it, and confirmed /api/gnss/position reports a moving fix across two polls.
73 lines
2.4 KiB
Ruby
Executable File
73 lines
2.4 KiB
Ruby
Executable File
#!/usr/bin/env ruby
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# frozen_string_literal: true
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# Speaks gpsd's own JSON wire protocol (https://gpsd.io/gpsd_json.html)
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# directly on gpsd's default port — GpsdClient (lib/maptool/gpsd_client.rb)
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# connects to it exactly as it would to real gpsd, so no app code or config
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# changes are needed. Unlike docs/development.adoc's fake-NMEA-source
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# example, this doesn't need gpsd itself installed/running at all, and
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# actually moves (a fixed point isn't much of a "GNSS position" to look
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# at) — drives a loop around a center point at a driving-ish pace, one TPV
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# report per second like a real receiver.
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#
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# Usage: bin/gnss_simulator.rb [lat] [lon] [radius_m] [port]
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require "socket"
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require "json"
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$stdout.sync = true
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LAT = (ARGV[0] || 48.1486).to_f
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LON = (ARGV[1] || 17.1077).to_f
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RADIUS_M = (ARGV[2] || 300).to_f
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PORT = (ARGV[3] || 2947).to_i
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LOOP_SECONDS = 120 # time to complete one full loop
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EARTH_RADIUS_M = 6_371_000
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def point_on_loop(center_lat, center_lon, radius_m, angle_rad)
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# Flat-plane offset, not geodesic — fine at this radius (metres, not km),
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# same reasoning as measure.js's own approximations at this scale.
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lat_offset = (radius_m * Math.sin(angle_rad)) / EARTH_RADIUS_M
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lon_offset = (radius_m * Math.cos(angle_rad)) / (EARTH_RADIUS_M * Math.cos(center_lat * Math::PI / 180))
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[center_lat + lat_offset * 180 / Math::PI, center_lon + lon_offset * 180 / Math::PI]
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end
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server = TCPServer.new("127.0.0.1", PORT)
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puts "[gnss-simulator] driving a #{RADIUS_M.to_i}m loop around #{LAT},#{LON} — listening on 127.0.0.1:#{PORT}"
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loop do
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socket = server.accept
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puts "[gnss-simulator] client connected"
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start = Time.now
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begin
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loop do
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elapsed = Time.now - start
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angle = (elapsed / LOOP_SECONDS) * 2 * Math::PI
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lat, lon = point_on_loop(LAT, LON, RADIUS_M, angle)
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# Bearing of travel: tangent to the circle, 90 degrees ahead of the
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# radius vector at this point.
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track = (angle * 180 / Math::PI + 90) % 360
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speed = (2 * Math::PI * RADIUS_M) / LOOP_SECONDS # m/s, constant pace
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report = {
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class: "TPV",
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mode: 3,
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lat: lat,
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lon: lon,
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altHAE: 150.0,
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speed: speed,
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track: track,
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eph: 3.0,
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time: Time.now.utc.strftime("%Y-%m-%dT%H:%M:%S.%3NZ"),
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}
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socket.puts(JSON.generate(report))
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sleep 1
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end
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rescue Errno::EPIPE, IOError
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puts "[gnss-simulator] client disconnected"
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ensure
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socket.close
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end
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end
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