From 3e03508e043123dbdc3ebb00ce6c67f12c8f8c47 Mon Sep 17 00:00:00 2001
From: Charles Karney <charles@karney.com>
Date: Wed, 11 Jul 2018 09:49:22 -0400
Subject: Fix #1074.  Fix unit conversion factors for geod.

Previously, unit conversion using atof(unit_list[i].to_meter) which
gives the wrong answer with, e.g., "1/10".  Now it directly uses
unit_list[i].factor (e.g., 0.1).

Also fix all the conversion factors for the US Surveyor units so that
they are the closest doubles.  E.g., the conversion factors for US
feet are

        factor              rel error
    old 0.304800609601219   6e-16
        12/39.37            1e-16
    now 1200/3937.0         5e-17

Maybe someone should check the Indian units (but it's possible that
India and Pakistan have different standards).
---
 src/geod_set.c |  2 +-
 src/pj_units.c | 16 ++++++++--------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/geod_set.c b/src/geod_set.c
index 479f18da..dacb0c73 100644
--- a/src/geod_set.c
+++ b/src/geod_set.c
@@ -37,7 +37,7 @@ geod_set(int argc, char **argv) {
 		for (i = 0; (s = unit_list[i].id) && strcmp(name, s) ; ++i) ;
 		if (!s)
 			emess(1,"%s unknown unit conversion id", name);
-		fr_meter = 1. / (to_meter = atof(unit_list[i].to_meter));
+		fr_meter = 1. / (to_meter = unit_list[i].factor);
 	} else
 		to_meter = fr_meter = 1.;
 	geod_f = es/(1 + sqrt(1 - es));
diff --git a/src/pj_units.c b/src/pj_units.c
index 59ff1ebe..e8421dea 100644
--- a/src/pj_units.c
+++ b/src/pj_units.c
@@ -12,12 +12,12 @@
 ** numerator/denomenator values (e.g. 1/1000) */
 C_NAMESPACE_VAR const struct PJ_UNITS
 pj_units[] = {
-    {"km",      "1000.",                "Kilometer",                    1000.0},
-    {"m",       "1.",                   "Meter",                        1.0},
+    {"km",      "1000",                 "Kilometer",                    1000.0},
+    {"m",       "1",                    "Meter",                        1.0},
     {"dm",      "1/10",                 "Decimeter",                    0.1},
     {"cm",      "1/100",                "Centimeter",                   0.01},
     {"mm",      "1/1000",               "Millimeter",                   0.001},
-    {"kmi",     "1852.0",               "International Nautical Mile",  1852.0},
+    {"kmi",     "1852",                 "International Nautical Mile",  1852.0},
     {"in",      "0.0254",               "International Inch",           0.0254},
     {"ft",      "0.3048",               "International Foot",           0.3048},
     {"yd",      "0.9144",               "International Yard",           0.9144},
@@ -25,11 +25,11 @@ pj_units[] = {
     {"fath",    "1.8288",               "International Fathom",         1.8288},
     {"ch",      "20.1168",              "International Chain",          20.1168},
     {"link",    "0.201168",             "International Link",           0.201168},
-    {"us-in",   "1./39.37",             "U.S. Surveyor's Inch",         0.0254},
-    {"us-ft",   "0.304800609601219",    "U.S. Surveyor's Foot",         0.304800609601219},
-    {"us-yd",   "0.914401828803658",    "U.S. Surveyor's Yard",         0.914401828803658},
-    {"us-ch",   "20.11684023368047",    "U.S. Surveyor's Chain",        20.11684023368047},
-    {"us-mi",   "1609.347218694437",    "U.S. Surveyor's Statute Mile", 1609.347218694437},
+    {"us-in",   "1/39.37",              "U.S. Surveyor's Inch",         100/3937.0},
+    {"us-ft",   "12/39.37",             "U.S. Surveyor's Foot",         1200/3937.0},
+    {"us-yd",   "36/39.37",             "U.S. Surveyor's Yard",         3600/3937.0},
+    {"us-ch",   "792/39.37",            "U.S. Surveyor's Chain",        79200/3937.0},
+    {"us-mi",   "63360/39.37",          "U.S. Surveyor's Statute Mile", 6336000/3937.0},
     {"ind-yd",  "0.91439523",           "Indian Yard",                  0.91439523},
     {"ind-ft",  "0.30479841",           "Indian Foot",                  0.30479841},
     {"ind-ch",  "20.11669506",          "Indian Chain",                 20.11669506},
-- 
cgit v1.2.3