diff --git a/index.js b/index.js
index 9d5d14e..4bc1cd5 100644
--- a/index.js
+++ b/index.js
@@ -11,7 +11,6 @@ const { validateGeoJson } = require('./src/utils.geojson.js')
 const port = process.env.PORT || 8080
 const bodyLimit = process.env.BODY_LIMIT || '100kb'
 const terrainFile = process.env.TERRAIN_FILEPATH || path.join('/mbtiles', 'terrain.mbtiles')
-const demFile = process.env.DEM_FILEPATH || path.join('/mbtiles', 'dem.vrt')
 
 // features validator middleware
 const geoJsonValidator = function (req, res, next) {
@@ -53,14 +52,10 @@ new MBTiles(terrainFile, (err, mbtiles) => {
     })
   })
 
-  app.get('/elevationat', (req, res) => {
-    return res.status(200).json({ foo: false })
-  })
-
   // Elevation
   app.post('/elevation', [geoJsonValidator], async (req, res) => {
     let start = new Date()
-    const result = await elevation(req.body, demFile)
+    const result = await elevation(req.body)
     let duration = new Date() - start
     console.log('<> profile computed in %dms', duration)
     return res.status(200).json(result)
diff --git a/src/elevation.js b/src/elevation.js
index 04108c7..6acb35c 100644
--- a/src/elevation.js
+++ b/src/elevation.js
@@ -81,10 +81,17 @@ async function parallel_exec(tasklist, concurrency) {
 }
 
 // based on https://kokoalberti.com/articles/creating-elevation-profiles-with-gdal-and-two-point-equidistant-projection/
-async function elevation(geojson, dem) {
+async function elevation(geojson) {
   // Extract computing parameters
   const resolution = _.get(geojson, 'resolution', 30)
   console.log('[K2] elevation requested with parameters: ', { resolution })
+  const concurrency = _.get(geojson, 'concurrency', 4)
+  const demOverride = _.get(geojson, 'demOverride', '')
+
+  // 1 arc sec is ~30m at the equator
+  // srtmv4 is 3arcsec => ~90m
+  // gmted2010 has 7.5, 15 and 30 arcsec => ~220m
+  const demFile = path.join('/mbtiles', demOverride !== '' ? demOverride : resolution < 220 ? 'srtm.vrt' : 'gmted2010.vrt')
 
    // prepare work folder
   const workDir = fs.mkdtempSync(path.join(os.tmpdir(), 'elevation-'))
@@ -122,7 +129,7 @@ async function elevation(geojson, dem) {
                       '-t_srs', `"${projStr}"`,
                       '-ts', numPoints, '1',
                       '-r', 'max',
-                      dem, outFile ], logFile)
+                      demFile, outFile ], logFile)
       },
       success: () => {},
       fail: () => {}
@@ -130,7 +137,7 @@ async function elevation(geojson, dem) {
     allTasks.push(task)
   })
 
-  await parallel_exec(allTasks, 4)
+  await parallel_exec(allTasks, concurrency)
 
   // we'll have to read each segment as tiff and generate a geojson points from data
   const segments = []