Ascent and descent values too high

[microteq]

Hi

Ascent and descent values are too high, because they are calculated every 1 to 4 meters. They should be calculated in bigger walking distances. My suggestion is 10 meters.

I have adjusted the source code, which is pasted at the end of this message. Only what I have marked with DGF are changes made by me, the rest is the original. There are two functions in leaflet-elevation.js that are affected: _addData and _addPoint.

Best regards.
Daniel.

---

/*
* Parsing data either from GPX or GeoJSON and update the diagram data
*/
_addData: function(d) {
let geom = d && d.geometry;
let feat = d && d.type === "FeatureCollection";
let gpx = d && d._latlngs;

		if (geom) {
			switch (geom.type) {
				case 'LineString':
					this._addGeoJSONData(geom.coordinates);
					break;

				case 'MultiLineString':
					geom.coordinates.forEach(coords => this._addGeoJSONData(coords));
					break;

				default:
					console.warn('Unsopperted GeoJSON feature geometry type:' + geom.type);
			}
      //DGF if elevation difference is too small, make ascent and descent equal
      if (Math.abs(this._ascent-this._descent) <= 10)
      {
        this.track_info.descent = this.track_info.ascent;
        this._descent = this.track_info.descent;
      }
      //DGF end
		}

		if (feat) {
			d.features.forEach(feature => this._addData(feature));
		}

		if (gpx) {
			this._addGPXdata(d._latlngs);
		}
	},

---

/*
* Parse and push a single (x, y, z) point to current elevation profile.
*/
_addPoint: function(x, y, z) {
if (this.options.reverseCoords) {
[x, y] = [y, x];
}

		let data = this._data || [];
		let eleMax = this._maxElevation || -Infinity;
		let eleMin = this._minElevation || +Infinity;
		let dist = this._distance || 0;
    //DGF
    let elevDist = this._elevationMesurementDistance || 0;
    //DGF end
		let curr = new L.LatLng(x, y);
		let prev = data.length ? data[data.length - 1].latlng : curr;

		let delta = curr.distanceTo(prev) * this._distanceFactor;

		dist = dist + Math.round(delta / 1000 * 100000) / 100000;
    //DGF
    elevDist = elevDist + delta;
    //DGF end

    // check and fix missing elevation data on last added point
		if (!this.options.skipNullZCoords && data.length > 0) 
    {
			let prevZ = data[data.length - 1].z;
			if (isNaN(prevZ)) {
				let lastZ = this._lastValidZ;
				let currZ = z * this._heightFactor;
				if (!isNaN(lastZ) && !isNaN(currZ)) {
					prevZ = (lastZ + currZ) / 2;
				} else if (!isNaN(lastZ)) {
					prevZ = lastZ;
				} else if (!isNaN(currZ)) {
					prevZ = currZ;
				}
				if (!isNaN(prevZ)) data[data.length - 1].z = prevZ;
				else data.splice(data.length - 1, 1);
			}
		}

		z = z * this._heightFactor;

		// skip point if it has not elevation
		if (!isNaN(z)) 
    {
			eleMax = eleMax < z ? z : eleMax;
			eleMin = eleMin > z ? z : eleMin;

      // calculate new ascent or descent
      //DGF measure elevation only every 10 meters of walking distance
      if (elevDist >= 10 || isNaN(this._lastMeasuredZ))
      {
        elevDist = 0;
        let dz = z - this._lastMeasuredZ ;  //DGF
        if (dz > 0)
        {
          this.track_info.ascent  = (this.track_info.ascent || 0) + dz;  // Total Ascent
          this._ascent = this.track_info.ascent;
        }
        else if (dz < 0)
        {
          this.track_info.descent = (this.track_info.descent || 0) - dz; // Total Descent
          this._descent = this.track_info.descent;
        }
        this._lastMeasuredZ = z;  //DGF
      }
      this._elevationMesurementDistance = elevDist;
      //DGF end
      this._lastValidZ = z;
			// set up last valid z value	
		}

		data.push({
			dist: dist,
			x: x,
			y: y,
			z: z,
			latlng: curr
		});

		this._data = data;
		this._distance = dist;
		this._maxElevation = eleMax;
		this._minElevation = eleMin;
	},

[morehawes]

@micrtoeq,

DGF are changes made by me, the rest is the original

Appreciated. I will look in to this.

Joe

[morehawes]

Originally discussed here. My thoughts:

I’m not sure what the best way to deal with this will be honestly. The ascent/descent values in question were added in a recent Pull Request and were pulled over from the Leaflet Elevation plugin that Waymark uses… but is not using the most recent version (I believe because of some conflicts I was not able to resolve a long time ago… but can’t quite remember).

So this is quite messy already and any other edits may compound the problem. I agree though that these values should be accurate and that user control over the measurement “frequency” (there is probably a more accurate term) would be a good solution.

Introduced in PR by @MaximeChallon.

Input/help welcome! This may have been discussed/addressed in the source project already so that's worth checking.