topic Print task scale bar accuracy question in ArcGIS JavaScript Maps SDK Questions

Print task scale bar accuracy question

MikeKillion — Mon, 10 Jun 2013 14:52:56 GMT

Hello,
I'm using the print task in v3.5 to output a pdf. The scalebar on the pdf is not accurate however, it's about 0.3 miles short when compared to section lines on the map (see attached pdf). I'm using the preserveScale = true option. I have the scalebar units set to miles, and have experimented with setting the units of the basemap as well - nothing makes an improvement.

Any thoughts?

Thanks

Re: Print task scale bar accuracy question

VinayBansal — Sat, 11 Dec 2021 11:00:23 GMT

Try giving width, height in export options of PrintTemplate

var plate = new esri.tasks.PrintTemplate();
    plate.format = "pdf";
    plate.layout = "MAP_ONLY"; 
    plate.exportOptions = {
        width: map.width,
        height: map.height,
        dpi: 96
    };

Re: Print task scale bar accuracy question

MikeKillion — Sat, 11 Dec 2021 11:00:26 GMT

Setting width and height in the export options had no effect.

Here's the print function I'm currently using:

function printPDF() {
  
  var printUrl = 'http://services.kgs.ku.edu/arcgis/rest/services/Utilities/PrintingTools/GPServer/Export%20Web%20Map%20Task';
  var printTask = new esri.tasks.PrintTask(printUrl);
        var params = new esri.tasks.PrintParameters();
        var template = new esri.tasks.PrintTemplate(); 
  
        template.layout = layout;     // layout set elsewhere
  template.format = "PDF";
        template.preserveScale = true;
  template.showAttribution = false;
  template.layoutOptions = {
   scaleBarUnit: "Miles",
   titleText: title,        // title set elsewhere
   legendLayers: []
  };
  

  params.map = app.map;
  params.outSpatialReference = sr;     // sr set elsewhere to 102100, also tried setting it to 3857
        params.template = template;

        printTask.execute(params, printResult, printError);
  
}

I don't expect it to be exact - I know our section lines aren't exactly a mile apart. But this seems way off. At a scale of about 1:72000, 2 miles on the scale bar is only about 1.5 miles on the map. Has anyone else noticed something like this? Can any ESRI folks comment?

Thanks,
Mike

Re: Print task scale bar accuracy question

JohnGravois — Tue, 11 Jun 2013 14:05:18 GMT

what is the coordinate system of your basemap?

Re: Print task scale bar accuracy question

MikeKillion — Tue, 11 Jun 2013 14:56:04 GMT

The basemap is the World_Topo_Map, so the spatial reference is 102100 (3857).

Re: Print task scale bar accuracy question

JohnGravois — Tue, 11 Jun 2013 15:16:38 GMT

that isn't a projection that preserves distance accurately, so it wouldn't be appropriate to display a scalebar.

Re: Print task scale bar accuracy question

MikeKillion — Tue, 11 Jun 2013 15:22:51 GMT

To remove the scalebar, do I have to create a custom mxd to use as a template?

Thanks

Re: Print task scale bar accuracy question

JohnGravois — Tue, 11 Jun 2013 15:44:38 GMT

no problem at all.

it wouldn't take long to publish additional services for printing. the steps in the tutorial explain that you are welcome to reuse (and tweak) our installed templates.

you can also feel free to navigate to the MXD template our OOTB print services utilize and remove the scalebar from that MXD if you prefer. (ex. .\Program Files\ArcGIS\Server\Templates\ExportWebMapTemplates\A3 Landscape.mxd)

Re: Print task scale bar accuracy question

BenFousek — Tue, 11 Jun 2013 16:45:28 GMT

Mike,
Another option is to set the projection of your print task template map to that of the data if you want to keep the scale bar and have it accurate. This can cause a slightly longer print task processing time with tiled web mercator layers.

Re: Print task scale bar accuracy question

JohnGravois — Tue, 11 Jun 2013 16:47:51 GMT

Another option is to set the projection of your print task template map to that of the data if you want to keep the scale bar and have it accurate

@ben
i dont think thats actually correct. its my understanding that the projection of the print output will be determined by the spatial reference which is passed within the WebMapJSON.

Re: Print task scale bar accuracy question

BenFousek — Tue, 11 Jun 2013 17:02:23 GMT

@ben
i dont think thats actually correct. its my understanding that the projection of the print output will be determined by the spatial reference which is passed within the WebMapJSON.

Yep. And here I had been using that reasoning for a couple of print tasks. Will be spending the day fixing that with an extent reprojection.

Re: Print task scale bar accuracy question

BenFousek — Tue, 11 Jun 2013 17:39:51 GMT

Will be spending the day fixing that with an extent reprojection.

Already taken care of. Set outSpatialReference of esri.tasks.PrintParameters.

Re: Print task scale bar accuracy question

JohnGravois — Tue, 11 Jun 2013 18:10:32 GMT

excellent. thanks for sharing!

Re: Print task scale bar accuracy question

MikeKillion — Wed, 12 Jun 2013 14:00:10 GMT

I was already setting the outSpatialReference when I was seeing the problem. It's set to 102100 to match the web map. Are you saying it should be set to match the spatial reference of the dataframe in the template mxd?

Re: Print task scale bar accuracy question

JohnGravois — Wed, 12 Jun 2013 14:06:26 GMT

i think Ben is suggesting setting the outSpatialReference to a coordinate system which accurately portrays distance.

Re: Print task scale bar accuracy question

BenFousek — Wed, 12 Jun 2013 14:13:59 GMT

Yes. You can output in any spatial reference you would like. So if your data is in some state plane projection you can set outSpatialReference to that projection and that will be what is output.

My mistake was thinking that if I set the projection of the data frame in the template it would output in that projection, but the print task overrides it. Foolishly I didn't test that theory. Setting outSpatialReference fixed it and I'm getting accurate scales.

If outSpatialReference is not set it uses the map's projection (102100).

You may also want to set preserveScale to false if your output has different units (feet not meters); else the extent of the output will be different than the map.

var template = esri.tasks.PrintTemplate(); template.preserveScale = false;

Re: Print task scale bar accuracy question

MikeKillion — Wed, 12 Jun 2013 14:25:47 GMT

That did it - I misunderstood what outSpatialReference did.

Thanks guys!