From 36b1284996c086c106c2e3a3c3054e6f34c1c9c1 Mon Sep 17 00:00:00 2001
From: Daniel <dan@telent.net>
Date: Sun, 18 May 2025 18:01:56 +0000
Subject: [PATCH] nmea: parse degrees and minutes in lat/long

---
 pkgs/maps/nmea.fnl | 53 +++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/pkgs/maps/nmea.fnl b/pkgs/maps/nmea.fnl
index fe999c5..d3516b2 100644
--- a/pkgs/maps/nmea.fnl
+++ b/pkgs/maps/nmea.fnl
@@ -54,6 +54,16 @@
       nil
       (tonumber s)))
 
+(fn parse-coordinate [value sign]
+  (if (= value "")
+      nil
+      (let [(deg min) (string.match value "(..)(.+)")]
+        (print :deg value deg :min min)
+        (*
+         (+ (tonumber deg)
+            (/ (tonumber min) 60))
+         (case sign :N 1 :E 1 :S -1 :W -1)))))
+
 (local
  msg-types
  {
@@ -66,14 +76,9 @@
            altitude _
            geoidal-separation _
            _ _ ] fields
-          latf (if (= lat "")
-                   nil
-                   (* (tonumber lat) 0.01 (case latsign :N 1 :S -1)))
-          lonf (if (= lon "")
-                   nil
-                   (* (tonumber lon) 0.01 (case lonsign :E 1 :W -1)))]
-      { :lat latf
-        :lon lonf
+          ]
+      { :lat (parse-coordinate lat latsign)
+        :lon (parse-coordinate lon lonsign)
         : fix-quality
         :total-space-vehicles (try-number total-space-vehicles)
         :hdop (try-number hdop)
@@ -86,39 +91,27 @@
         knots bearing-true date
         magn-var magn-var-sign
         mode nav-status &as fields]]
-    (let [latf (if (= lat "")
-                   nil
-                   (* (tonumber lat) 0.01 (case latsign :N 1 :S -1)))
-          lonf (if (= lon "")
-                   nil
-                   (* (tonumber lon) 0.01 (case lonsign :E 1 :W -1)))
-          magnetic-variation (if (= magn-var "")
+    (let [magnetic-variation (if (= magn-var "")
                                  nil
                                  (* (tonumber magn-var)
                                     (case magn-var-sign :E 1 :W -1)))]
       { : utc
         : valid
-        :lat latf
-        :lon lonf
+        :lat (parse-coordinate lat latsign)
+        :lon (parse-coordinate lon lonsign)
         :speed-knots (try-number knots)
         :bearing-true (try-number bearing-true)
         : date
-        : magnetic-variation
+        : magnetic-variation ;;; XXX probably wrong
         : mode
         }))
 
   :GNS
   (fn [fields]
     (let [[utc lat latsign lon lonsign mode total-space-vehicles
-           hdop altitude geoidal-separation _ _ nav-status] fields
-          latf (if (= lat "")
-                   nil
-                   (* (tonumber lat) 0.01 (case latsign :N 1 :S -1)))
-          lonf (if (= lon "")
-                   nil
-                   (* (tonumber lon) 0.01 (case lonsign :E 1 :W -1)))]
-      { :lat latf
-        :lon lonf
+           hdop altitude geoidal-separation _ _ nav-status] fields]
+      { :lat (parse-coordinate lat latsign)
+        :lon (parse-coordinate lon lonsign)
         : mode
         :total-space-vehicles (try-number total-space-vehicles)
         :hdop (try-number hdop)
@@ -150,14 +143,16 @@
           (tset :talker talker))
         split)))
 
+;; XXX this is wrong. 5131.348976 is 51 degrees 31.348976 minutes
+
 (expect=
  (parse-line
   "$GNGNS,111134.00,5131.348976,N,00005.551003,W,AAAANN,19,0.7,20.3,47.0,,,V*0C\n")
  {:altitude 20.3
   :geoidal-separation 47
   :hdop 0.7
-  :lat 51.31348976
-  :lon -0.05551003
+  :lat 51.522482933333
+  :lon -0.092516716666667
   :message-type "GNS"
   :mode "AAAANN"
   :nav-status "V"