diff --git a/frontend/src/Main.elm b/frontend/src/Main.elm
index c04328d..7a548c8 100644
--- a/frontend/src/Main.elm
+++ b/frontend/src/Main.elm
@@ -24,7 +24,7 @@ import Svg.Attributes as S exposing
     , fill
     , stroke, strokeWidth, strokeOpacity)
 import Time
-import TileMap exposing (..) -- (tiles, FineZoomLevel, toZoomCoord, toCoord)
+import TileMap exposing (..)
 import Url.Parser exposing (Parser, (<?>), int, map, s, string)
 import Url.Parser.Query as Query
 import Url exposing (Url)
@@ -80,7 +80,7 @@ init _ url navKey =
     in
         ((Model
               (toCoord (Pos 0 0 Nothing))
-              (FineZoomLevel (1*8)) None 0 0 (0,0) Loading),
+              (ZoomLevel (1*8)) None 0 0 (0,0) Loading),
              (fetchTrack start duration))
 
 -- SUBSCRIPTIONS
@@ -187,7 +187,7 @@ updateModel msg model =
                     { model
                         | track = Present trk
                         , centre = toCoord (Point.centre trk)
-                        , zoom = FineZoomLevel (13  * 8)
+                        , zoom = ZoomLevel (13  * 8)
                         , startTime = start
                         , duration = duration
                         , markedTime = (start + 300, duration - 900)
@@ -454,7 +454,7 @@ powerView = measureView "power" "#994444" (.power >> Maybe.map toFloat)
 
 eleView = measureView "elevation" "#4444ee" (.pos >> .ele)
 
-trackView : Int -> Int -> FineZoomLevel -> List Point -> Svg Msg
+trackView : Int -> Int -> ZoomLevel -> List Point -> Svg Msg
 trackView leftedge topedge zoom points =
     let plot p =
             let (x, y) = pixelFromCoord (toCoord p.pos) zoom
@@ -499,7 +499,7 @@ ifTrack model content =
         Loading -> div [] [Html.text "loading"]
         Empty -> div [] [Html.text "no points"]
 
-canvas : Coord -> FineZoomLevel -> Int -> Int -> Model -> Html Msg
+canvas : Coord -> ZoomLevel -> Int -> Int -> Model -> Html Msg
 canvas centre zoom width height model =
     let tm = TileMap centre zoom width height
         mapBounds = TileMap.bounds tm
diff --git a/frontend/src/Model.elm b/frontend/src/Model.elm
index 3231fd7..9a6fe24 100644
--- a/frontend/src/Model.elm
+++ b/frontend/src/Model.elm
@@ -5,7 +5,7 @@ module Model exposing
     , Drag(..)
     , DragTarget(..)
     )
-import TileMap exposing (FineZoomLevel, Coord)
+import TileMap exposing (ZoomLevel, Coord)
 import Point exposing (Point)
 
 type DragTarget = Map | Graph | StartMark | EndMark | NoTarget
@@ -18,7 +18,7 @@ type TrackState = Empty | Loading | Failure String | Present (List Point)
 
 type alias Model =
     { centre: Coord
-    , zoom: FineZoomLevel
+    , zoom: ZoomLevel
     , drag: Drag
     , startTime : Float
     , duration : Float
diff --git a/frontend/src/TileMap.elm b/frontend/src/TileMap.elm
index 87605b1..2ed9d8f 100644
--- a/frontend/src/TileMap.elm
+++ b/frontend/src/TileMap.elm
@@ -1,6 +1,5 @@
 module TileMap exposing (tiles
-                        , FineZoomLevel(..)
-                        , ZoomLevel
+                        , ZoomLevel(..)
                         , Coord
                         , TileMap(..)
                         , toCoord
@@ -24,21 +23,21 @@ type alias TileNumber = { x: Int, y: Int }
 type alias Coord = { x: Float, y: Float }
 
 -- zoom level
-type alias ZoomLevel = Int
-type FineZoomLevel = FineZoomLevel Int
+type alias TileZoomLevel = Int
+type ZoomLevel = ZoomLevel Int
 
 
-type TileMap = TileMap Coord FineZoomLevel Int Int
+type TileMap = TileMap Coord ZoomLevel Int Int
 
 zoomStep = 8
 
-toZoom : FineZoomLevel -> ZoomLevel
-toZoom (FineZoomLevel f) = f // zoomStep
+toZoom : ZoomLevel -> TileZoomLevel
+toZoom (ZoomLevel f) = f // zoomStep
 
 
-incZoom : FineZoomLevel -> Int -> FineZoomLevel
-incZoom (FineZoomLevel z) delta =
-    FineZoomLevel (clamp 0 (20 * zoomStep) (z + delta))
+incZoom : ZoomLevel -> Int -> ZoomLevel
+incZoom (ZoomLevel z) delta =
+    ZoomLevel (clamp 0 (20 * zoomStep) (z + delta))
 
 
 -- project lat/long to co-ordinates based on pseudocode at
@@ -68,15 +67,15 @@ reflect c = Coord -c.x -c.y
 translate base offset =
     { x = (base.x + offset.x), y = (base.y + offset.y) }
 
-translatePixels : Coord -> FineZoomLevel -> (Int, Int) -> Coord
+translatePixels : Coord -> ZoomLevel -> (Int, Int) -> Coord
 translatePixels old z_ (x, y) =
     translate old (pixelsToCoord z_ (x, y))
 
-tileCovering : Coord -> ZoomLevel -> TileNumber
+tileCovering : Coord -> TileZoomLevel -> TileNumber
 tileCovering c z =
     TileNumber (truncate (toFloat (2 ^ z) * c.x)) (truncate (toFloat (2 ^ z) * c.y))
 
-pixelFromCoord : Coord -> FineZoomLevel -> (Int, Int)
+pixelFromCoord : Coord -> ZoomLevel -> (Int, Int)
 pixelFromCoord c z_ =
     let z = toZoom z_
         {x,y} = tileCovering c (z + 8)
@@ -104,7 +103,7 @@ bounds tmap =
     }
 
 
-tileUrl : TileNumber -> ZoomLevel -> String
+tileUrl : TileNumber -> TileZoomLevel -> String
 tileUrl {x,y} z =
     String.concat ["https://a.tile.openstreetmap.org",
                        "/", String.fromInt z,