Scale bar accuracy and units in the Print Task

[EddieStathopoulos]

Hello,

I have been attempting to add print capabilities to an application using the ExportWebMap spec and I have two questions/concerns:

1) Does setting the scalebarUnit of a PrintTemplate (aka scaleBarOptions for the ExportWebMap spec) actually do anything besides change the labels for the scale bar?

As far as I can tell, changing this value does nothing more than provide different labels which means the scale bar is grossly inaccurate (ignoring spatial reference inaccuracies). Correct me if I'm wrong, but this certainly looks like a bug. I've attached images to show this in action. The scale bars are identical (other than labels). If this is the case, what is the purpose of this option?

2) Can I get an accurate scale bar even if I am in a spatial reference not ideal for measurements?

Measure tools will often use Great-Circle distance to get more accurate distances. There are many situations where only Web Mercator tiles are available but an accurate scale bar is desired. Is this possible or will I have to roll my own solution?

For reference, I am hitting the esri sample Export Web Map Task. I will be extending this service (and already have) but have been using the default to ensure it is not my implementation at fault.

Thanks,
Eddie

[Anonymous User]

Original User: jeff.pace

1. this does look like a very bad bug
2. there are updates to the measurement widget coming.  However, I would temper your expectations.  I am inferring that (based on your screenshot) you will be billing for a permit based on some measurement.  If this is correct, please dont do this.  Web GIS is informational, not legal.  You should be billing off measurements on an asbuilt/survey, in my opinion.

[EddieStathopoulos]

I thought it was a pretty nasty bug! It looks like I will just disable changing units in my print widget.

As for the printed scalebar, I understand it is not legal (and that will not be the use), but much like the measure tool, there are circumstances where people want as-close-to-reliable information as they can get from GIS to use as a baseline. Otherwise, I could make the exact argument against using measure tools.

I look forward to the Measure tool updates; however, we are currently using our own implementation which seems to be doing okay. For the scalebar on printed templates, I suppose I will venture into creating my own implementation or solution.

Thanks for the quick response Jeff! 🙂

[MattReeves]

Good Morning Eddie,

We are noticing a pretty extreme (50% or so) difference between the measurement tools findings, and the scalebar in the print widgets generated printouts. You made the comment above 'For the scalebar on printed templates, I supposed I will venture into creating my own implementation or solution', I was hoping to pry a little on this, and see if you were successful in creating a solution/work around here. We'd like to show the scale bar on the print outs, but currently they are grossly inaccurate as compared to the measure tool. We are running WAB Dev 2.0.

I look forward to your feedback.

Thanks,

Matt

[Anonymous User]

Original User: jeff.pace

Are you on support? Please submit this as a bug.

I agree with the accuracy argument, and make the same case to my users.

I actually remove the scale bar from my prints 😉

[EddieStathopoulos]

I just submitted the bug.

I actually remove the scale bar from my prints 😉

Haha, I'm with you on this one. I'll take less work anyday! 😄