diff --git a/dat/themerms.lua b/dat/themerms.lua
index 2b6587b5b..4b2aeb05d 100644
--- a/dat/themerms.lua
+++ b/dat/themerms.lua
@@ -80,8 +80,7 @@ themerooms = {
                     if (percent(25)) then
                        local mintime = 1000 - (nh.level_difficulty() * 100);
                        local ice_melter = function(x,y)
-                          local ax,ay = nh.abscoord(x,y);
-                          nh.start_timer_at(ax,ay, "melt-ice", mintime + nh.rn2(1000));
+                          nh.start_timer_at(x,y, "melt-ice", mintime + nh.rn2(1000));
                        end;
                        ice:iterate(ice_melter);
                     end
diff --git a/doc/lua.adoc b/doc/lua.adoc
index e3f571a7a..e0959480d 100644
--- a/doc/lua.adoc
+++ b/doc/lua.adoc
@@ -6,13 +6,16 @@
 
 Functions exposed from the NetHack core. They are all in the `nh` table.
 
+All core functions involving xy coordinates interpret these as relative to the
+last defined map or room.
+
 === abscoord
 
-Convert a room-relative coordinate to map-absolute.
+Convert a room- or map-relative coordinate to absolute.
 Can accept one table with x and y keys (and in that case, returns similar),
 or two integer values (and returns two integer values)
-des-routines tend to use relative coordinates, nh and obj use absolute.
-(This mess is still very much in need of improvement.)
+des, nh, and obj routines all treat inputs as relative coordinates, but this is
+here in case an absolute one is needed for some reason (debugging?).
 
 Example:
 
@@ -385,6 +388,9 @@ Example:
 
 Functions for creating special levels. They are in the `des` table.
 
+All special level functions involving xy coordinates interpret these as relative
+to the last defined map or room.
+
 === altar
 
 Create an altar of certain type and alignment.
diff --git a/include/extern.h b/include/extern.h
index 6b4156bcd..c1234b848 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -2610,6 +2610,8 @@ extern void selection_do_gradient(struct selectionvar *, long, long, long,
 extern int lspo_reset_level(lua_State *);
 extern int lspo_finalize_level(lua_State *);
 extern boolean get_coord(lua_State *, int, lua_Integer *, lua_Integer *);
+extern void cvt_to_abscoord(coordxy *, coordxy *);
+extern void cvt_to_relcoord(coordxy *, coordxy *);
 extern int nhl_abs_coord(lua_State *);
 extern void update_croom(void);
 extern const char *get_trapname_bytype(int);
diff --git a/src/nhlobj.c b/src/nhlobj.c
index d9e46e6f0..32c8b02d2 100644
--- a/src/nhlobj.c
+++ b/src/nhlobj.c
@@ -363,6 +363,8 @@ l_obj_at(lua_State *L)
 
         x = (coordxy) luaL_checkinteger(L, 1);
         y = (coordxy) luaL_checkinteger(L, 2);
+        cvt_to_abscoord(&x, &y);
+
         lua_pop(L, 2);
         (void) l_obj_push(L, g.level.objects[x][y]);
         return 1;
@@ -386,6 +388,8 @@ l_obj_placeobj(lua_State *L)
 
     x = (coordxy) luaL_checkinteger(L, 2);
     y = (coordxy) luaL_checkinteger(L, 3);
+    cvt_to_abscoord(&x, &y);
+
     lua_pop(L, 3);
 
     if (lobj_is_ok(lo)) {
@@ -569,6 +573,7 @@ l_obj_bury(lua_State *L)
     } else if (argc == 3) {
         x = (coordxy) lua_tointeger(L, 2);
         y = (coordxy) lua_tointeger(L, 3);
+        cvt_to_abscoord(&x, &y);
     } else
         nhl_error(L, "l_obj_bury: Wrong args");
 
@@ -617,7 +622,7 @@ l_obj_register(lua_State *L)
     luaL_setfuncs(L, l_obj_meta, 0);
     /* metatable.__index points at the object method table. */
     lua_pushvalue(L, -2);
-    lua_setfield(L, -2, "__index"); 
+    lua_setfield(L, -2, "__index");
 
     /* Don't let lua code mess with the real metatable.
        Instead offer a fake one that only contains __gc. */
diff --git a/src/nhlsel.c b/src/nhlsel.c
index 3f766abc9..085ac5996 100644
--- a/src/nhlsel.c
+++ b/src/nhlsel.c
@@ -839,7 +839,10 @@ l_selection_gradient(lua_State *L)
     return 1;
 }
 
-/* sel:iterate(function(x,y) ... end); */
+/* sel:iterate(function(x,y) ... end);
+ * The x, y coordinates passed to the function are map- or room-relative
+ * rather than absolute, unless there has been no previous map or room defined.
+ */
 static int
 l_selection_iterate(lua_State *L)
 {
@@ -854,9 +857,11 @@ l_selection_iterate(lua_State *L)
         for (y = rect.ly; y <= rect.hy; y++)
             for (x = max(1,rect.lx); x <= rect.hx; x++)
                 if (selection_getpoint(x, y, sel)) {
+                    coordxy tmpx = x, tmpy = y;
+                    cvt_to_relcoord(&tmpx, &tmpy);
                     lua_pushvalue(L, 2);
-                    lua_pushinteger(L, x - g.xstart);
-                    lua_pushinteger(L, y - g.ystart);
+                    lua_pushinteger(L, tmpx);
+                    lua_pushinteger(L, tmpy);
                     if (nhl_pcall(L, 2, 0)) {
                         impossible("Lua error: %s", lua_tostring(L, -1));
                         /* abort the loops to prevent possible error cascade */
diff --git a/src/nhlua.c b/src/nhlua.c
index dafee5753..2b74fd84c 100644
--- a/src/nhlua.c
+++ b/src/nhlua.c
@@ -172,7 +172,7 @@ void
 nhl_error(lua_State *L, const char *msg)
 {
     lua_Debug ar;
-    char buf[BUFSZ];
+    char buf[BUFSZ*2];
 
     lua_getstack(L, 1, &ar);
     lua_getinfo(L, "lS", &ar);
@@ -389,6 +389,7 @@ nhl_gettrap(lua_State *L)
     }
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (isok(x, y)) {
             struct trap *ttmp = t_at(x,y);
@@ -439,7 +440,8 @@ nhl_deltrap(lua_State *L)
     }
     x = (coordxy) lx;
     y = (coordxy) ly;
-    
+    cvt_to_abscoord(&x, &y);
+
     if (isok(x, y)) {
         struct trap *ttmp = t_at(x,y);
 
@@ -452,6 +454,11 @@ nhl_deltrap(lua_State *L)
 /* get parameters (XX,YY) or ({ x = XX, y = YY }) or ({ XX, YY }),
    and set the x and y values.
    return TRUE if there are such params in the stack.
+   Note that this does not adjust the values of x and y at all from what is
+   specified in the level file; so, it returns absolute coordinates rather than
+   map-relative coordinates. Callers of this function must decide if they want
+   to interpret the values as absolute or as map-relative, and adjust
+   accordingly.
  */
 boolean
 nhl_get_xy_params(lua_State *L, lua_Integer *x, lua_Integer *y)
@@ -487,23 +494,9 @@ nhl_getmap(lua_State *L)
         nhl_error(L, "Incorrect arguments");
         return 0;
     }
-    if (g.in_mklev) {
-        /* xstart and ystart are set by the des.map() command to give
-         * coordinates relative to the 0,0 of that map. It can be quite useful
-         * to check what terrain is on a given space. But without compensating
-         * for the change in xstart and ystart here, this will lead to results
-         * like des.terrain(4,6,'L') and then nh.getmap(4,6) not being lava.
-         *
-         * Only valid during mklev, because xstart and ystart are not saved
-         * with the level and can change during the level creating process when
-         * additional des.map() are executed. They will not necessarily be the
-         * same later. */
-        x += g.xstart;
-        y += g.ystart;
-    }
-
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (isok(x, y)) {
             char buf[BUFSZ];
@@ -1177,6 +1170,7 @@ nhl_timer_has_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (isok(x, y)) {
         when = spot_time_expires(x, y, timertype);
@@ -1205,6 +1199,7 @@ nhl_timer_peek_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (timer_is_pos(timertype) && isok(x, y))
         when = spot_time_expires(x, y, timertype);
@@ -1230,6 +1225,7 @@ nhl_timer_stop_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (timer_is_pos(timertype) && isok(x, y))
         spot_stop_timers(x, y, timertype);
@@ -1254,6 +1250,7 @@ nhl_timer_start_at(lua_State *L)
 
     x = (coordxy) lx;
     y = (coordxy) ly;
+    cvt_to_abscoord(&x, &y);
 
     if (timer_is_pos(timertype) && isok(x, y)) {
         long where = ((long) x << 16) | (long) y;
diff --git a/src/sp_lev.c b/src/sp_lev.c
index dfa3feaae..60e5ee8ca 100644
--- a/src/sp_lev.c
+++ b/src/sp_lev.c
@@ -1150,11 +1150,15 @@ rndtrap(void)
 }
 
 /*
- * Coordinates in special level files are handled specially:
+ * Translate a given coordinate from a special level definition into an actual
+ * location on the map.
  *
- *      if x or y is < 0, we generate a random coordinate.
- *      The "humidity" flag is used to ensure that engravings aren't
- *      created underwater, or eels on dry land.
+ * If x or y is negative, we generate a random coordinate within the area. If
+ * not negative, they are interpreted as relative to the last defined map or
+ * room, and are output as absolute g.level.locations coordinates.
+ *
+ * The "humidity" flag is used to ensure that engravings aren't created
+ * underwater, or eels on dry land.
  */
 static void
 get_location(
@@ -3085,6 +3089,12 @@ get_table_montype(lua_State *L, int *mgender)
     return ret;
 }
 
+/* Get x and y values from a table (which the caller has already checked for the
+ * existence of), handling both a table with x= and y= specified and a table
+ * with coord= specified.
+ * Returns absolute rather than map-relative coordinates; the caller of this
+ * function must decide if it wants to interpret the coordinates as map-relative
+ * and adjust accordingly. */
 static void
 get_table_xy_or_coord(lua_State *L, lua_Integer *x, lua_Integer *y)
 {
@@ -5237,7 +5247,56 @@ l_table_getset_feature_flag(
     }
 }
 
-/* convert relative coordinate to map-absolute.
+/* guts of nhl_abs_coord; convert a coordinate relative to a map or room into an
+ * absolute coordinate in g.level.locations.
+ *
+ * If there is no enclosing map or room, the coordinates are assumed to be
+ * absolute already.
+ *
+ * Part of the reason this is a function is to make it clearer in the calling
+ * code that this conversion is what is intended.
+ *
+ * NOTE: if the coordinates are going to get passed to one of the get_location
+ * family of functions, this should NOT be called; get_location already makes
+ * an adjustment like this. (What this function supports which get_location
+ * doesn't is the input coordinates being negative. get_location will treat that
+ * as "level designer wants a random coordinate".) */
+void
+cvt_to_abscoord(coordxy *x, coordxy *y)
+{
+    /* since commit 99715e0, xstart and ystart are only relevant in mklev when
+     * maps are being used, and 0 otherwise. It is possible in the future that
+     * map positions and dimensions can be saved and retrieved outside of mklev
+     * which would reintroduce nonzero xstart/ystart/xsiz/ysiz, but this is not
+     * currently implemented, so this function can be assumed to have no effect
+     * outside of mklev.
+     */
+    if (g.coder && g.coder->croom) {
+        *x += g.coder->croom->lx;
+        *y += g.coder->croom->ly;
+    }
+    else {
+        *x += g.xstart;
+        *y += g.ystart;
+    }
+}
+
+/* inverse of cvt_to_abscoord; turn an absolute g.level.locations coordinate
+ * into one relative to the current map or room. */
+void
+cvt_to_relcoord(coordxy *x, coordxy *y)
+{
+    if (g.coder && g.coder->croom) {
+        *x -= g.coder->croom->lx;
+        *y -= g.coder->croom->ly;
+    }
+    else {
+        *x -= g.xstart;
+        *y -= g.ystart;
+    }
+}
+
+/* convert map-relative coordinate to absolute.
   local ax,ay = nh.abscoord(rx, ry);
   local pt = nh.abscoord({ x = 10, y = 5 });
  */
@@ -5250,16 +5309,14 @@ nhl_abs_coord(lua_State *L)
     if (argc == 2) {
         x = (coordxy) lua_tointeger(L, 1);
         y = (coordxy) lua_tointeger(L, 2);
-        x += g.xstart;
-        y += g.ystart;
+        cvt_to_abscoord(&x, &y);
         lua_pushinteger(L, x);
         lua_pushinteger(L, y);
         return 2;
     } else if (argc == 1 && lua_type(L, 1) == LUA_TTABLE) {
         x = (coordxy) get_table_int(L, "x");
         y = (coordxy) get_table_int(L, "y");
-        x += g.xstart;
-        y += g.ystart;
+        cvt_to_abscoord(&x, &y);
         lua_newtable(L);
         nhl_add_table_entry_int(L, "x", x);
         nhl_add_table_entry_int(L, "y", y);
diff --git a/test/test_des.lua b/test/test_des.lua
index d0163f2c5..afd7fcb4d 100644
--- a/test/test_des.lua
+++ b/test/test_des.lua
@@ -3,7 +3,7 @@
 -- reset_level is only needed here, not in normal special level scripts.
 
 function is_map_at(x,y, mapch, lit)
-   local rm = nh.getmap(x + 1, y); -- + 1 == g.xstart
+   local rm = nh.getmap(x, y);
    if rm.mapchr ~= mapch then
       error("Terrain at (" .. x .. "," .. y .. ") is not \"" .. mapch .. "\", but \"" .. rm.mapchr .. "\"");
    end
@@ -29,7 +29,7 @@ function check_loc_flag(x, y, flag, value)
 end
 
 function check_trap_at(x,y, name)
-   local t = nh.gettrap(x + 1, y); -- + 1 == g.xstart
+   local t = nh.gettrap(x, y);
    if (t.ttyp_name ~= name) then
       error("Trap at " .. x .. "," .. y .. " is " .. t.ttyp_name .. ", not " .. name);
    end
@@ -211,10 +211,10 @@ LTL]])
 FFF
 F.F
 FFF]] })
-   for x = 60, 62 do
-      for y = 5, 7 do
+   for x = 0,2 do
+      for y = 0,2 do
          local nam = "iron bars";
-         if (x == 61 and y == 6) then
+         if (x == 1 and y == 1) then
              nam = "room";
          end
          check_loc_name(x, y, nam);
@@ -224,10 +224,10 @@ FFF]] })
 ...
 .T.
 ...]] })
-   for x = 60, 62 do
-      for y = 5, 7 do
+   for x = 0, 2 do
+      for y = 0, 2 do
          local nam = "room";
-         if (x == 61 and y == 6) then
+         if (x == 1 and y == 1) then
              nam = "tree";
          end
          check_loc_name(x, y, nam);
@@ -244,50 +244,50 @@ III]] })
                 des.terrain(0,0, "L");
                 des.terrain(map.width-1,map.height-1, "T");
    end});
-   check_loc_name(30, 5, "lava pool");
-   check_loc_name(32, 7, "tree");
+   check_loc_name(0, 0, "lava pool");
+   check_loc_name(2, 2, "tree");
 end
 
 function test_feature()
    des.reset_level();
    des.level_init({ style = "solidfill", fg = ".", lit = 1 });
    des.feature("fountain", 40, 08);
-   check_loc_name(40 + 1, 08, "fountain");
+   check_loc_name(40, 08, "fountain");
    des.feature("sink", {41, 08});
-   check_loc_name(41 + 1, 08, "sink");
+   check_loc_name(41, 08, "sink");
    des.feature({ type = "pool", x = 42, y = 08 });
-   check_loc_name(42 + 1, 08, "pool");
+   check_loc_name(42, 08, "pool");
    des.feature({ type = "sink", coord = {43, 08} });
-   check_loc_name(43 + 1, 08, "sink");
+   check_loc_name(43, 08, "sink");
 
    des.feature({ type = "throne", coord = {44, 08}, looted=true });
-   check_loc_name(44 + 1, 08, "throne");
-   check_loc_flag(44 + 1, 08, "looted", true);
+   check_loc_name(44, 08, "throne");
+   check_loc_flag(44, 08, "looted", true);
 
    des.feature({ type = "throne", coord = {44, 08}, looted=false });
-   check_loc_name(44 + 1, 08, "throne");
-   check_loc_flag(44 + 1, 08, "looted", false);
+   check_loc_name(44, 08, "throne");
+   check_loc_flag(44, 08, "looted", false);
 
    des.feature({ type = "tree", coord = {45, 08}, looted=true, swarm=false });
-   check_loc_name(45 + 1, 08, "tree");
-   check_loc_flag(45 + 1, 08, "looted", true);
-   check_loc_flag(45 + 1, 08, "swarm", false);
+   check_loc_name(45, 08, "tree");
+   check_loc_flag(45, 08, "looted", true);
+   check_loc_flag(45, 08, "swarm", false);
 
    des.feature({ type = "tree", coord = {45, 08}, looted=false, swarm=true });
-   check_loc_name(45 + 1, 08, "tree");
-   check_loc_flag(45 + 1, 08, "looted", false);
-   check_loc_flag(45 + 1, 08, "swarm", true);
+   check_loc_name(45, 08, "tree");
+   check_loc_flag(45, 08, "looted", false);
+   check_loc_flag(45, 08, "swarm", true);
 
    des.feature({ type = "fountain", coord = {46, 08}, looted=false, warned=true });
-   check_loc_name(46 + 1, 08, "fountain");
-   check_loc_flag(46 + 1, 08, "looted", false);
-   check_loc_flag(46 + 1, 08, "warned", true);
+   check_loc_name(46, 08, "fountain");
+   check_loc_flag(46, 08, "looted", false);
+   check_loc_flag(46, 08, "warned", true);
 
    des.feature({ type = "sink", coord = {47, 08}, pudding=false, dishwasher=true, ring=true });
-   check_loc_name(47 + 1, 08, "sink");
-   check_loc_flag(47 + 1, 08, "pudding", false);
-   check_loc_flag(47 + 1, 08, "dishwasher", true);
-   check_loc_flag(47 + 1, 08, "ring", true);
+   check_loc_name(47, 08, "sink");
+   check_loc_flag(47, 08, "pudding", false);
+   check_loc_flag(47, 08, "dishwasher", true);
+   check_loc_flag(47, 08, "ring", true);
 end
 
 function test_gold()
diff --git a/test/test_sel.lua b/test/test_sel.lua
index 72c40896c..72c450456 100644
--- a/test/test_sel.lua
+++ b/test/test_sel.lua
@@ -40,7 +40,7 @@ function sel_are_equal(sela, selb, msg)
 end
 
 function is_map_at(x,y, mapch, lit)
-   local rm = nh.getmap(x + 1, y); -- + 1 == g.xstart
+   local rm = nh.getmap(x, y); 
    if rm.mapchr ~= mapch then
       error("Terrain at (" .. x .. "," .. y .. ") is not \"" .. mapch .. "\", but \"" .. rm.mapchr .. "\"");
    end