diff --git a/Dockerfile b/Dockerfile
index beb9c3d..cb65887 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,13 +2,10 @@ FROM ghcr.io/sdr-enthusiasts/docker-baseimage:base AS build
 
 RUN set -x && \
     apt-get update -y && \
-    apt-get install -q -o Dpkg::Options::="--force-confnew" -y --no-install-recommends \
+    apt-get install -q -o Dpkg::Options::="--force-confnew" -y \
         git gcc && \
     cd / && \
-    git clone --depth=1 --single-branch https://github.com/sdr-enthusiasts/docker-vesselalert.git && \
-    cd /docker-vesselalert/src && \
-    # make the output in meters instead of nautical miles:
-    sed -i 's|/ 1852.0||g' distance.c && \
+    curl -sSL https://raw.githubusercontent.com/sdr-enthusiasts/docker-adsb-ultrafeeder/main/downloads/distance.c -o /distance.c && \
     gcc -static distance.c -o distance -lm -Ofast
 
 FROM ghcr.io/sdr-enthusiasts/docker-tar1090:latest
diff --git a/downloads/distance.c b/downloads/distance.c
new file mode 100644
index 0000000..d87c2da
--- /dev/null
+++ b/downloads/distance.c
@@ -0,0 +1,69 @@
+/*
+---------------------------------------------------------------------------------------------
+Copyright (C) 2002-2022, Chris Veness
+Adaptations Copyright (C) 2023, John Norrbin (JohnEx)
+Adaptations (C) 2023, Ramon F. Kolb (kx1t)
+
+MIT License:
+
+Permission is hereby granted, free of charge, to any person 
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without 
+restriction, including without limitation the rights to use, 
+copy, modify, merge, publish, distribute, sublicense, and/or 
+sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following 
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
+THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+---------------------------------------------------------------------------------------------
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#define PI 3.14159265
+
+// https://www.movable-type.co.uk/scripts/latlong.html
+double distance(double lat_a, double lon_a, double lat_b, double lon_b)
+{
+
+    double lat_a_scaled = lat_a * (double)PI / 180.0;
+    double lat_b_scaled = lat_b * (double)PI / 180.0;
+    double lat_delta = (lat_b - lat_a) * (double)PI / 180.0;
+    double lon_delta = (lon_b - lon_a) * (double)PI / 180.0;
+
+    double a = sin(lat_delta / 2.0) * sin(lat_delta / 2.0) + cos(lat_a_scaled) * cos(lat_b_scaled) * sin(lon_delta / 2.0) * sin(lon_delta / 2.0);
+    double c = 2.0 * atan2(sqrt(a), sqrt(1.0 - a));
+
+    return 6372797.56085 * c;
+}
+
+
+int main(int argc, char *argv[])
+{
+    if (argc != 5)
+    {
+        printf("Usage: distance lat1 lon1 lat2 lon2\n");
+        return 1;
+    }
+
+    double lat1 = atof(argv[1]);
+    double lon1 = atof(argv[2]);
+    double lat2 = atof(argv[3]);
+    double lon2 = atof(argv[4]);
+
+    double d = distance(lat1, lon1, lat2, lon2);
+    printf("%f\n", d);
+    return 0;
+}