topic Re: Wrong final radius drawing a circle in ArcGIS Pro Questions

Wrong final radius drawing a circle

RonaldoKnychala — Fri, 02 Nov 2018 20:00:58 GMT

Hi, I'm having problems when drawing a circle entering the radius. I start creating circle, enter a radius (eg. 1200feet) and after it's done the circle ends up with less than what've I entered (eg.1020 feet), can anyone tell what I'm doing wrong ? TKS!

Re: Wrong final radius drawing a circle

DanPatterson_Retired — Fri, 02 Nov 2018 20:49:05 GMT

are your visuals a different example since the numbers don't match... but I do see some inner and outer radius thing going on

Re: Wrong final radius drawing a circle

RonaldoKnychala — Fri, 02 Nov 2018 21:07:19 GMT

Yes the visual are different too, what do you mean by inner and outer radius?

Sent from my iPhone

Re: Wrong final radius drawing a circle

DanPatterson_Retired — Sat, 03 Nov 2018 10:47:11 GMT

I just tried with drawing a simple radius for a circle and I get the expected perimeter and area for a circle with a radius of 1000m

Re: Wrong final radius drawing a circle

RonaldoKnychala — Tue, 06 Nov 2018 12:26:57 GMT

Hi Dan, yes yours look just right, mine when I do that the result is different.. IDK what to do

Re: Wrong final radius drawing a circle

DanPatterson_Retired — Tue, 06 Nov 2018 12:41:30 GMT

It appears measurement issues are related to a coordinate system having 'tainted' the map. Anything that may be added first to a map (or dataframe) sets the coordinate system. I always suspect Web Mercator as the root problem when the measurement differences aren't purely a meters vs feet issue.

Re: Wrong final radius drawing a circle

RonaldoKnychala — Tue, 06 Nov 2018 13:54:06 GMT

Tks for your insights Dan, yes I'm using Web Mercartor WGS 1984, and working with feet on my measurements, you thinks that's the problem? Should I change my spatial reference?

Re: Wrong final radius drawing a circle

DanPatterson_Retired — Tue, 06 Nov 2018 15:17:10 GMT

That IS the problem. Web Mercator produces erroneous measurements for length, perimeter and area. It is well documented, but continue to use it for some reason

FAQ: Why are my map, distance and area measurements wrong when using WGS 1984 Web Mercator?

And it isn't just esri, but anything 'Googly' that does mapping. It is designed for looking at.,. not doing with. Until they have automatic 'fixes' in all software, we have banned anything 'webbie' as basemaps or layers in our teaching, because the temptation to 'measure' something in some software that use it is too great

Re: Wrong final radius drawing a circle

RonaldoKnychala — Tue, 06 Nov 2018 15:26:05 GMT

Tks Dan, I'm from Brazil and there I was using SIRGAS 2000, recently I moved to Texas USA and thought that WGS 84 would be suitable, didn't know about that issue. Tks for letting me know!!

Re: Wrong final radius drawing a circle

JoshuaBixby — Tue, 06 Nov 2018 18:04:08 GMT

Not to nitpick, but the issue isn't with WGS84. There is nothing wrong, inaccurate, or imprecise about the WGS84 datum, it is the Web Mercator projection based on WGS84 datum that creates these issues.

Re: Wrong final radius drawing a circle

DanPatterson_Retired — Wed, 07 Nov 2018 01:59:19 GMT

Kory Kramer‌ is there a general request to disable any 'measurement tool' should Web Mercator be the working projection?

It sounds too fuzzy and general for ArcGIS Ideas‌ but, corrections, warnings or disable are pretty well the only options. This is increasingly becoming an issue

Perhaps if you come across some insights you could get them shared here.

Leaving this thread 'open' might serve as a warning and a reference point