Graham McIntire
b4206b63d1
Fixed issue where stationary stations like K5SGD-D were showing multiple positions due to minor GPS accuracy variations. The previous 15-meter threshold was too strict for typical GPS drift which can vary 5-30 meters. - Increased default threshold in GeoUtils from 10m to 50m - Updated packet processor to use 50m threshold for movement detection - Verified with K5SGD-D showing ~24m variations that are now ignored 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>
50 lines
1.5 KiB
Elixir
50 lines
1.5 KiB
Elixir
defmodule Aprsme.GeoUtils do
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@moduledoc """
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Geographic utility functions for calculating distances and related operations.
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"""
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@earth_radius_meters 6_371_000
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@doc """
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Calculate the Haversine distance between two points in meters.
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## Examples
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iex> Aprsme.GeoUtils.haversine_distance(33.16961, -96.4921, 33.16962, -96.4921)
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1.11
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"""
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def haversine_distance(lat1, lon1, lat2, lon2)
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when is_number(lat1) and is_number(lon1) and is_number(lat2) and is_number(lon2) do
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# Convert to radians
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lat1_rad = lat1 * :math.pi() / 180
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lat2_rad = lat2 * :math.pi() / 180
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dlat_rad = (lat2 - lat1) * :math.pi() / 180
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dlon_rad = (lon2 - lon1) * :math.pi() / 180
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# Haversine formula
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a =
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:math.sin(dlat_rad / 2) * :math.sin(dlat_rad / 2) +
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:math.cos(lat1_rad) * :math.cos(lat2_rad) *
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:math.sin(dlon_rad / 2) * :math.sin(dlon_rad / 2)
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c = 2 * :math.atan2(:math.sqrt(a), :math.sqrt(1 - a))
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# Distance in meters
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@earth_radius_meters * c
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end
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def haversine_distance(_, _, _, _), do: nil
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@doc """
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Check if the distance between two points exceeds a minimum threshold.
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This helps filter out GPS drift and insignificant movements.
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Default threshold is 50 meters to account for typical GPS accuracy variations.
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"""
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def significant_movement?(lat1, lon1, lat2, lon2, threshold_meters \\ 50) do
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case haversine_distance(lat1, lon1, lat2, lon2) do
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nil -> false
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distance -> distance > threshold_meters
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end
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end
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end
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