topic Re: Scale setting widget in ArcGIS Web AppBuilder Questions

Scale setting widget

SimonCrutchley — Mon, 12 Nov 2018 12:39:52 GMT

Is there a widget in Web App Builder to allow you to set a fixed scale at which a map appears? Ideally you could enter the scale, but if not a pick list would do?

Simon

Re: Scale setting widget

Anonymous User — Mon, 12 Nov 2018 22:02:31 GMT

I would love to see this as well, and it would be nice to be able to create a list of scales and also let users pick their own absolute scale. Also it would be good to display scale ie 1:2,000 above the scale bar, as an option. Last, allow the display to have text with units the developers choose, like 1 inch = 100 feet. This has long been a user question and for now I have to show them how to go to Print, then Advanced, then click 'current' by Scale. Thus it would be helpful if scale was intuitive and discoverable.

Re: Scale setting widget

SimonCrutchley — Tue, 13 Nov 2018 09:44:25 GMT

Good to see others would like it; a pity it's not been picked up yet. I suspect my request is slightly different to yours, as it's not just printing at a set scale, but actually viewing. Within our team we're used to viewing our mapped data at set scales, so you can instantly orientate yourself to relative feature sizes etc. Hence we like to know that this view is 1:20,000 not 1:10,000.

Re: Scale setting widget

RichBell — Tue, 13 Nov 2018 13:12:00 GMT

Mahoning County solved this issue for our cadastral team using an RF scale and the set scale LODS in the main config file. Look under the title, as a user scrolls with the mouse the true scale changes and this enables the print function to print to a set scale for output.

Hope this helps.

Rich

Re: Scale setting widget

SimonCrutchley — Tue, 13 Nov 2018 14:14:51 GMT

Hi Rich. Thanks for that, but I'm a bit of a newbie; RF scale and LODS?

Re: Scale setting widget

RobertScheitlin__GISP — Tue, 13 Nov 2018 14:16:45 GMT

Having a widget for zoom to scale would be pretty simple. The issue is that when working with a Cached basemap you are confined to the cache LODs (levels of display. Scales that the map service was cached at). So If I were to develop a widget for this then most of the time you would not get an option to type the scale you desire because you would only be able to zoom to those pre-determined LODs (scales). So as a developer I would present a dropdown with those scales matching the LODs. In the rare circumstance that the app does not use a basemap then there could be a text input that the user could type any scale into (as that would now be possible).

Re: Scale setting widget

SimonCrutchley — Tue, 13 Nov 2018 14:21:29 GMT

Sorry, but i'm still confused. By the map service, do you mean the basemap that is being used or the map created with all the layers etc? If the former I guess we're stumped as we can't control it; if the later can you do something in the map?

Re: Scale setting widget

RobertScheitlin__GISP — Tue, 13 Nov 2018 14:37:15 GMT

Simon,

The basemap that is used (which is normally just a cached map service) sets the maps LODs, which constrains the maps scales that are available to be zoomed to.

Re: Scale setting widget

SimonCrutchley — Tue, 13 Nov 2018 14:42:25 GMT

Thanks for the clarification. I've been speaking to a colleague who thinks that we use a bespoke map base, so might be able to control it. I'll look into this further and, if it is possible, will come back to look at the possibility of a widget.

Re: Scale setting widget

RichBell — Tue, 13 Nov 2018 15:19:07 GMT

The base map is the issue...

Create your own base map with the correct WKID.

Post this base map to your ArcGIS online account, this is now your "itemId:"

Create your scale lodes in the Config. Each click of the mouse moves to a defined LOD

Example:

Re: Scale setting widget

SimonCrutchley — Tue, 13 Nov 2018 15:21:00 GMT

Hi Rich,

So how did you get the scale to appear, as that in itself would be useful? I know how to add a scale bar, but not to display the scale.

Simon

Re: Scale setting widget

RichBell — Tue, 13 Nov 2018 15:29:41 GMT

Here Ya go!

Add this widget to your project.

Re: Scale setting widget

SimonCrutchley — Tue, 13 Nov 2018 16:29:24 GMT

Thanks Rich. I'm pretty sure I'll have to talk to someone in the main GIS team to work out just what I'm doing, but I'm sure they'll understand this.

Re: Scale setting widget

SimonCrutchley — Wed, 14 Nov 2018 13:40:49 GMT

Hi folks,

Thanks for all your help. This could technically be seen as a separate question, but since you all seem very knowledgeable in this area I thought I'd ask. The "co-ordinates" widget doesn't seem to be working in so far as there is no running display. I can click on the widget and it will then add a marker for which it gives me the co-ordinates, but I'm used to it just giving a running display as you move the mouse around.

Any ideas why this should be?

Re: Scale setting widget

RobertScheitlin__GISP — Wed, 14 Nov 2018 14:04:39 GMT

Simon,

The coordinate widget will only give a running display if the basemap is in Web mercator (102100) or geographic (4326) spatial references.

Re: Scale setting widget

SimonCrutchley — Wed, 14 Nov 2018 14:21:33 GMT

Hi Robert,

That's strange as it seems to work fine in my other app with British National Grid?

Why is that?

Re: Scale setting widget

RobertScheitlin__GISP — Wed, 14 Nov 2018 14:43:44 GMT

Simon,

If the basemap is web mercator and you coordinate display is web mercator or geographic then running coordinates will display. If the display coordinate system is not the same as the basemap then the coordinates will have to be re-projected and this can not be done in realtime.

Re: Scale setting widget

Anonymous User — Fri, 16 Nov 2018 14:42:48 GMT

While basemaps have defined LODs with the Esri/Google/Bing system can't they reproject on the fly from the esri server? I did that years ago with a custom JS API app. Although I do remember they looked a little uglier, I think when it reprojected back then, it spit out as a jpeg with low compression. I don't mean the fact that it would resample, which it would do of course to fit the new projection, but I could also tell there were also jpeg artifacts. Nevertheless ability to define absolute scale would be very useful. If it is a map app used for field measurement then having nice, even scales to make maps to measure in the field off of is useful to engineers and other folks. Just a thought. And even before they implement that just showing the absolute scale text, and a note like 1"=100' or 1 inch = 100 feet (US) would be nice to add the WAB scalebar widget. Interesting the coordinates could not reproject in real time that would not seem like too much computation but maybe I'm wrong. I had also noticed that and wished it worked in real time for state plane (my app is 3857 of course, due to my previous experience with compressed basemap tiles); so I project my vector data to 3857 for loading speed.

Re: Scale setting widget

RobertScheitlin__GISP — Fri, 16 Nov 2018 14:51:15 GMT

While basemaps have defined LODs with the Esri/Google/Bing system can't they reproject on the fly from the esri server?

No. A basemap is a cached layer and cached means that there are tiles that are in a certain projection based at certain scales, that are generated before hand. There is nothing dynamic about a cached basemap (i.e. nothing can be changed at runtime). If you choose to add the layer as an ArcGISDynamicMapServiceLayer instead of ArcGISTiledMapServiceLayer to a basemap layer then yes you can re-project on the fly but you loose all the advantages of ArcGISTiledMapServiceLayer caches.

Re: Scale setting widget

Anonymous User — Mon, 19 Nov 2018 19:29:35 GMT

Oh yes that is what I meant, they were loaded as dynamic 'map image' layers. And remarkably degraded the dynamic raster looked in comparison the tiled one. Sorry I should indeed have written more clearly - I mean the coordinates can't they be re-projected in real time? Wouldn't seem like that heavy of a lift as a calculation? But I am just guessing there on that. And it's germane because I offer state plane (in dec. degrees and DMS) as well as 3857 to display coordinates in my viewer. I mention all this because I wish the coordinates would also update their display in real time as the cursor moves when in state plane and not just 3857.