topic Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK? in ArcGIS JavaScript Maps SDK Questions

How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

Sparkles — Wed, 12 Jun 2024 16:33:19 GMT

I want the natural elevation at each point in a polyline (using SketchWidget in arcGIS SDK for Javascript). For example if the polyline runs over a mountain , I'd want the z values of each point in the polyline to be different, to reflect the natural elevation

I tried changing the elevationInfo mode of the GraphicsLayer for the SketchWidget to all of the possible settings.

With "absolute-height" - the elevation of the first point in the polyline is set as the z value of all the points (even though the elevation changes as my polyline runs over mountains)...

With "relative-to-ground", "relative-to-scene", and "on-the-ground", the z value of each point is 0. (Which makes sense, as it is giving the altitude RELATIVE to the terrain...)

No option seems to give the natural terrain elevation at each point.

Thanks for the help!

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

Sparkles — Wed, 12 Jun 2024 16:35:20 GMT

Also, is there a callback that gets triggered at each point in the polyline? Sketch.on("create") only gets triggered at the first point. Thanks!

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

JamesIng — Thu, 13 Jun 2024 02:52:00 GMT

@Sparkles

Someone else had a similar question around getting elevation for a point / polyline which I answered in this link:

https://community.esri.com/t5/arcgis-javascript-maps-sdk-questions/how-to-know-the-altitude-of-a-point/m-p/1475359#M84660

As for your question about callback there is also Sketch.on("update") which will trigger per update to the sketch.
You can then grab the latest sketch from that from the event graphic array.

The last set of co-ordinates in your path would be the last drawn point in a polyline.

e.g:

... sketchViewModel.on(["update"], onGraphicUpdate); function onGraphicUpdate(event) { const graphic = event.graphics[0]; console.log('graphic', graphic) }

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

GreteSoosalu — Thu, 13 Jun 2024 09:37:54 GMT

Hi @Sparkles

Are you experiencing this while drawing a new line?

In this case the "problem" is that the elevation constraint gets applied. This makes all vertices be drawn at the elevation of the first one. You can disable the elevation constraint by enabling the tooltips, using Tab to enter the tooltips' input mode, and clicking on the lock icon next to the elevation/z field. Note that this needs to be done per feature.

From the SketchViewModel documentation:

When sketching polygons or polylines, the elevation constraint is applied by default. This means that all vertices use the z-value of the first vertex. To unlock the elevation constraint while sketching, make sure the tooltips and their inputs are enabled, and activate the input mode with the Tab key.

This behavior got introduced with version 4.29 in order to unify the drawing experience of polylines and polygons. But when drawing both, it is now possible to opt-out from this planar drawing mode.

Hope this helps you further. Let me know in case you have any other questions.

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

ChristopheSuter — Fri, 16 May 2025 12:51:08 GMT

Hi @GreteSoosalu ,

Is there any way to opt-out this planar drawing mode using the js sdk ?

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

GreteSoosalu — Fri, 16 May 2025 13:42:09 GMT

Hi @ChristopheSuter,

Currently, one needs to disable this planar behavior every time when starting to draw a new feature.

Are you looking for a way to make it a default behavior for the whole app? If so, could you explain a bit the context: is it needed for both lines and polygons; should the person who's drawing be able to change this setting?
Knowing more details will help us to prioritize and implement this enhancement in the future.

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

ChristopheSuter — Fri, 16 May 2025 13:53:37 GMT

Hi @GreteSoosalu, thanks for your reply. I am using sketchViewModel in my development. When using snappingOptions, since this is default behavior (planar sketching), results in a drawing that is difficult to understand for the users since the drawn shape does not snap to the features vertices/segments but above (or below) them at a fixed z.

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

GreteSoosalu — Mon, 19 May 2025 12:57:29 GMT

Thanks for the explanation. Could you also give an example of what these features/segments depict?

The current default behavior was designed for drawing features that are often planar (building footprints, schematic utilities, etc). In these cases, one can use snapping to sort-of fetch the X-Y values from vertices further away, while the Z still remains "locked" and the resulting geometry remains planar.

We can look into making it easier for apps to override this default.

Re: How to get elevation at points/paths in a polyline Sketch in arcGIS JavascriptSDK?

ChristopheSuter — Mon, 19 May 2025 13:24:19 GMT

It is for an custom measurement tool .. would be great if you could add any property to the sketchViewmodel to override that default ..