diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3b3249a..37b3f1f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,8 +7,18 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ## [Unreleased]
 ### Added
 - MUF and foF2 maps from [prop.kc2g.com](https://prop.kc2g.com/).
+### Changed
+- New colour theme for `?greyline`.
+- Moved great circle distance and bearing calculation from `?ungrid` to `?griddistance`.
+- `?ungrid` to `?latlong`.
+### Deprecated
+- `?ungrid`.
+
+
+## [2.5.1] - 2020-12-10
 ### Fixed
 - The result of `?greyline` was cached by discord and would get out of date.
+- Broken reaction functionality in `?hamstudy`.
 
 
 ## [2.5.0] - 2020-10-31
@@ -142,7 +152,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ## 1.0.0 - 2019-07-31 [YANKED]
 
 
-[Unreleased]: https://github.com/miaowware/qrm2/compare/v2.5.0...HEAD
+[Unreleased]: https://github.com/miaowware/qrm2/compare/v2.5.1...HEAD
+[2.5.1]: https://github.com/miaowware/qrm2/releases/tag/v2.5.1
 [2.5.0]: https://github.com/miaowware/qrm2/releases/tag/v2.5.0
 [2.4.1]: https://github.com/miaowware/qrm2/releases/tag/v2.4.1
 [2.4.0]: https://github.com/miaowware/qrm2/releases/tag/v2.4.0
diff --git a/exts/grid.py b/exts/grid.py
index b6b9618..f83b9d3 100644
--- a/exts/grid.py
+++ b/exts/grid.py
@@ -8,7 +8,7 @@ the GNU General Public License, version 2.
 """
 
 
-import math
+import gridtools
 
 import discord.ext.commands as commands
 
@@ -20,124 +20,49 @@ class GridCog(commands.Cog):
         self.bot = bot
 
     @commands.command(name="grid", category=cmn.cat.maps)
-    async def _grid_sq_lookup(self, ctx: commands.Context, lat: str, lon: str):
-        ("""Calculates the grid square for latitude and longitude coordinates, """
-         """with negative being latitude South and longitude West.""")
-        grid = "**"
-        latf = float(lat) + 90
-        lonf = float(lon) + 180
-        if 0 <= latf <= 180 and 0 <= lonf <= 360:
-            grid += chr(ord("A") + int(lonf / 20))
-            grid += chr(ord("A") + int(latf / 10))
-            grid += chr(ord("0") + int((lonf % 20)/2))
-            grid += chr(ord("0") + int((latf % 10)/1))
-            grid += chr(ord("a") + int((lonf - (int(lonf/2)*2)) / (5/60)))
-            grid += chr(ord("a") + int((latf - (int(latf/1)*1)) / (2.5/60)))
-            grid += "**"
-            embed = cmn.embed_factory(ctx)
-            embed.title = f"Maidenhead Grid Locator for {float(lat):.6f}, {float(lon):.6f}"
-            embed.description = grid
-            embed.colour = cmn.colours.good
-        else:
-            embed = cmn.embed_factory(ctx)
-            embed.title = f"Error generating grid square for {lat}, {lon}."
-            embed.description = """Coordinates out of range.
-                                The valid ranges are:
-                                - Latitude: `-90` to `+90`
-                                - Longitude: `-180` to `+180`"""
-            embed.colour = cmn.colours.bad
+    async def _grid_sq_lookup(self, ctx: commands.Context, lat: float, lon: float):
+        ("""Calculates the grid square for latitude and longitude coordinates."""
+         """\n\nCoordinates should be in decimal format, with negative being latitude South and longitude West."""
+         """\n\nTo calculate the latitude and longitude from a grid locator, use `latlong`""")
+        latlong = gridtools.LatLong(lat, lon)
+        grid = gridtools.Grid(latlong)
+
+        embed = cmn.embed_factory(ctx)
+        embed.title = f"Maidenhead Grid Locator for {latlong.lat:.5f}, {latlong.long:.5f}"
+        embed.description = f"**{grid}**"
+        embed.colour = cmn.colours.good
         await ctx.send(embed=embed)
 
-    @commands.command(name="ungrid", aliases=["loc"], category=cmn.cat.maps)
-    async def _location_lookup(self, ctx: commands.Context, grid: str, grid2: str = None):
-        """Calculates the latitude and longitude for the center of a grid square.
-        If two grid squares are given, the distance and azimuth between them is calculated."""
-        if grid2 is None or grid2 == "":
-            try:
-                grid = grid.upper()
-                loc = get_coords(grid)
+    @commands.command(name="latlong", aliases=["latlon", "loc", "ungrid"], category=cmn.cat.maps)
+    async def _location_lookup(self, ctx: commands.Context, grid: str):
+        ("""Calculates the latitude and longitude for the center of a grid locator."""
+         """\n\nTo calculate the grid locator from a latitude and longitude, use `grid`"""
+         """\n\n*Warning: `ungrid` will be removed soon. Use one of the other names for this command.*""")
+        grid_obj = gridtools.Grid(grid)
 
-                embed = cmn.embed_factory(ctx)
-                embed.title = f"Latitude and Longitude for {grid}"
-                embed.colour = cmn.colours.good
-
-                if len(grid) >= 6:
-                    embed.description = f"**{loc[0]:.5f}, {loc[1]:.5f}**"
-                    embed.url = f"https://www.openstreetmap.org/#map=13/{loc[0]:.5f}/{loc[1]:.5f}"
-                else:
-                    embed.description = f"**{loc[0]:.1f}, {loc[1]:.1f}**"
-                    embed.url = f"https://www.openstreetmap.org/#map=10/{loc[0]:.1f}/{loc[1]:.1f}"
-            except Exception as e:
-                embed = cmn.embed_factory(ctx)
-                embed.title = f"Error generating latitude and longitude for grid {grid}."
-                embed.description = str(e)
-                embed.colour = cmn.colours.bad
-        else:
-            radius = 6371
-            try:
-                grid = grid.upper()
-                grid2 = grid2.upper()
-                loc = get_coords(grid)
-                loc2 = get_coords(grid2)
-                # Haversine formula
-                d_lat = math.radians(loc2[0] - loc[0])
-                d_lon = math.radians(loc2[1] - loc[1])
-                a = (math.sin(d_lat/2) ** 2
-                     + math.cos(math.radians(loc[0]))
-                     * math.cos(math.radians(loc2[0]))
-                     * math.sin(d_lon/2) ** 2)
-                c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))
-                d = radius * c
-                d_mi = 0.6213712 * d
-
-                # Bearing
-                y_dist = math.sin(math.radians(loc2[1]-loc[1])) * math.cos(math.radians(loc2[0]))
-                x_dist = (math.cos(math.radians(loc[0]))
-                          * math.sin(math.radians(loc2[0]))
-                          - math.sin(math.radians(loc[0]))
-                          * math.cos(math.radians(loc2[0]))
-                          * math.cos(math.radians(loc2[1] - loc[1])))
-                bearing = (math.degrees(math.atan2(y_dist, x_dist)) + 360) % 360
-
-                embed = cmn.embed_factory(ctx)
-                embed.title = f"Great Circle Distance and Bearing from {grid} to {grid2}"
-                embed.description = f"**Distance:** {d:.1f} km ({d_mi:.1f} mi)\n**Bearing:** {bearing:.1f}°"
-                embed.colour = cmn.colours.good
-            except Exception as e:
-                embed = cmn.embed_factory(ctx)
-                embed.title = f"Error generating great circle distance and bearing from {grid} and {grid2}."
-                embed.description = str(e)
-                embed.colour = cmn.colours.bad
+        embed = cmn.embed_factory(ctx)
+        embed.title = f"Latitude and Longitude for {grid_obj}"
+        embed.colour = cmn.colours.good
+        embed.description = f"**{grid_obj.lat:.5f}, {grid_obj.long:.5f}**"
+        if ctx.invoked_with == "ungrid":
+            embed.add_field(name="Warning", value=(f"*`{ctx.prefix}ungrid` will be removed soon, use `{ctx.prefix}help "
+                                                   "latlong` to see other names for this command.*"))
         await ctx.send(embed=embed)
 
+    @commands.command(name="griddistance", aliases=["griddist", "distance", "dist"], category=cmn.cat.maps)
+    async def _dist_lookup(self, ctx: commands.Context, grid1: str, grid2: str):
+        """Calculates the great circle distance and azimuthal bearing between two grid locators."""
+        g1 = gridtools.Grid(grid1)
+        g2 = gridtools.Grid(grid2)
 
-def get_coords(grid: str):
-    if len(grid) < 3:
-        raise ValueError("The grid locator must be at least 4 characters long.")
+        dist, bearing = gridtools.grid_distance(g1, g2)
+        dist_mi = 0.6214 * dist
 
-    if not grid[0:2].isalpha() or not grid[2:4].isdigit():
-        if len(grid) <= 4:
-            raise ValueError("The grid locator must be of the form AA##.")
-        if len(grid) >= 6 and not grid[5:7].isalpha():
-            raise ValueError("The grid locator must be of the form AA##AA.")
-
-    lon = ((ord(grid[0]) - ord("A")) * 20) - 180
-    lat = ((ord(grid[1]) - ord("A")) * 10) - 90
-    lon += ((ord(grid[2]) - ord("0")) * 2)
-    lat += ((ord(grid[3]) - ord("0")) * 1)
-
-    if len(grid) >= 6:
-        # have subsquares
-        lon += ((ord(grid[4])) - ord("A")) * (5/60)
-        lat += ((ord(grid[5])) - ord("A")) * (2.5/60)
-        # move to center of subsquare
-        lon += (2.5/60)
-        lat += (1.25/60)
-        return (lat, lon)
-    # move to center of square
-    lon += 1
-    lat += 0.5
-    return (lat, lon)
+        embed = cmn.embed_factory(ctx)
+        embed.title = f"Great Circle Distance and Bearing from {g1} to {g2}"
+        embed.description = f"**Distance:** {dist:.1f} km ({dist_mi:.1f} mi)\n**Bearing:** {bearing:.1f}°"
+        embed.colour = cmn.colours.good
+        await ctx.send(embed=embed)
 
 
 def setup(bot: commands.Bot):
diff --git a/exts/image.py b/exts/image.py
index c6b72e7..9a834dc 100644
--- a/exts/image.py
+++ b/exts/image.py
@@ -17,8 +17,7 @@ import common as cmn
 
 
 class ImageCog(commands.Cog):
-    gl_url = ("http://www.fourmilab.ch/cgi-bin/uncgi/Earth?img=NOAAtopo.evif"
-              "&imgsize=320&dynimg=y&opt=-p&lat=&lon=&alt=&tle=&date=0&utc=&jd=")
+    gl_url = "https://www.fourmilab.ch/cgi-bin/uncgi/Earth?img=ETOPO1_day-m.evif&dynimg=y&opt=-p"
 
     def __init__(self, bot: commands.Bot):
         self.bot = bot
diff --git a/info.py b/info.py
index 4fd73fd..04b38c1 100644
--- a/info.py
+++ b/info.py
@@ -12,5 +12,5 @@ authors = ("@ClassAbbyAmplifier#2229", "@0x5c#0639")
 description = """A bot with various useful ham radio-related functions, written in Python."""
 license = "Released under the GNU General Public License v2"
 contributing = "Check out the source on GitHub, contributions welcome: https://github.com/miaowware/qrm2"
-release = "2.5.0"
+release = "2.5.1"
 bot_server = "https://discord.gg/Ntbg3J4"
diff --git a/main.py b/main.py
index a58aa7b..fcb0fc2 100644
--- a/main.py
+++ b/main.py
@@ -57,7 +57,7 @@ bot = commands.Bot(command_prefix=opt.prefix,
                    case_insensitive=True,
                    description=info.description, help_command=commands.MinimalHelpCommand(),
                    intents=intents,
-                   member_cache=member_cache,
+                   member_cache_flags=member_cache,
                    loop=loop,
                    connector=connector)
 
diff --git a/requirements.txt b/requirements.txt
index b950af8..b5f62b8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,6 @@
 discord.py~=1.5.0
 ctyparser~=2.0
+gridtools~=1.0
 beautifulsoup4
 lxml
 pytz