diff --git a/Cargo.lock b/Cargo.lock
index b5164d3..3a8aed6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -208,7 +208,7 @@ dependencies = [
 
 [[package]]
 name = "fit2gpx"
-version = "0.5.4"
+version = "0.5.5"
 dependencies = [
  "clap",
  "env_logger",
@@ -418,9 +418,9 @@ dependencies = [
 
 [[package]]
 name = "srtm_reader"
-version = "0.4.2"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ae82b5e949a85ec77c28ff244fd1277682cd6ecbd4749bec8ee5197365ab75ec"
+checksum = "73b7e8508865adf213782be9d2fc7a0b15183e18c68dddb46e6e4cba3a5cb5ff"
 
 [[package]]
 name = "strsim"
diff --git a/Cargo.toml b/Cargo.toml
index 4351367..40ff56f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "fit2gpx"
-version = "0.5.4"
+version = "0.5.5"
 edition = "2021"
 
 authors = ["Jeromos Kovács <iitsnotme214@proton.me>"]
@@ -20,7 +20,7 @@ geo-types = "0.7.15"
 gpx = "0.10.0"
 log = "0.4.25"
 rayon = "1.10.0"
-srtm_reader = { version = "0.4.2", optional = true }
+srtm_reader = { version = "0.5.0", optional = true }
 time = { version = "0.3.37", default-features = false }
 
 [features]
diff --git a/src/elevation.rs b/src/elevation.rs
index e9d1a64..f63fde6 100644
--- a/src/elevation.rs
+++ b/src/elevation.rs
@@ -6,12 +6,15 @@ pub use std::{
     path::Path,
 };
 
+/// truncated coordinate
+pub type Coord = (i8, i16);
+
 // TODO: docs
-pub fn needed_tile_coords(wps: &[Waypoint]) -> BTreeSet<(i32, i32)> {
-    // kinda Waypoint to (i32, i32)
-    let trunc = |wp: &Waypoint| -> (i32, i32) {
+pub fn needed_tile_coords(wps: &[Waypoint]) -> BTreeSet<Coord> {
+    // kinda Waypoint to Coord
+    let trunc = |wp: &Waypoint| -> Coord {
         let (x, y) = wp.point().x_y();
-        (y.trunc() as i32, x.trunc() as i32)
+        (y.trunc() as i8, x.trunc() as i16)
     };
     // tiles we need
     wps.par_iter()
@@ -22,7 +25,7 @@ pub fn needed_tile_coords(wps: &[Waypoint]) -> BTreeSet<(i32, i32)> {
 
 // TODO: docs
 pub fn read_needed_tiles(
-    needs: &BTreeSet<(i32, i32)>,
+    needs: &BTreeSet<Coord>,
     elev_data_dir: impl AsRef<Path>,
 ) -> Vec<srtm_reader::Tile> {
     log::info!("reading needed tiles into memory");
@@ -31,7 +34,7 @@ pub fn read_needed_tiles(
     let elev_data_dir = elev_data_dir.as_ref();
     needs
         .par_iter()
-        .map(|c| srtm_reader::get_filename(*c))
+        .map(|c| srtm_reader::Coord::from(*c).get_filename())
         .map(|t| elev_data_dir.join(t))
         .flat_map(|p| {
             srtm_reader::Tile::from_file(&p)