Latest Contributions by ShannonBelmont

well Duh.  I didn't test putting projected data in the map. Seems very obvious now that I know this was the "glitch". It seems like a big change from Desktop, to not be able to rely on projecting on the fly and 'borrowing' a projection from the data frame.  But with your explanation of extent densification, I see why Esri is trying to control or constrain the trouble many blindly get into.     And about your comment on web mercator auxilliary sphere!  Most of my instruction about CSs is to demonstrate how ridiculous measurements are if left in Web Mercator.  Esri has taken two major lab exercises off the table with this change. At first I was resistant to the idea of HAVING to reproject data because I've always been told there is a small erosion in the precision of the data each time you permanently change projection. I thought projecting on the fly was a great way to use display coordinate systems to supply the best CS for the analysis or measurement. But maybe I am simply resistant to change. And also working from a much more rudimentary place than others like yourself.  I am coming at this from the perspective of an instructor, not from the research or hard core analysis side. I am trying to demonstrate some of these basic concepts with CSs.  I'll just have to get more creative.  I'll be reading up on densification. Thanks a lot for this conversation, Dan. I've never used GeoNet before and found this to be incredibly helpful.  ... View more

I 100% agree with 'everything is an abstraction'! I focus a lot of my material and exercises on demonstrating this.  I think there might be some kind of glitch. If you have time, check out the attached images. I don't have the option to create planar calculations in ArcGIS Pro.  You can see that the map's display CS is set to a projected one yet I only have the option to calculate area and perimeter geodesically. Here you can see that even using the tool you suggested, I don't have the option to create "planar" attribute fields.  (I have the map CS set to a projection.) I've taught coordinate systems in ArcMap Desktop for 10 years. I'm learning ArcGIS Pro and switching my material over. From my experience with it (and the student who is working with me) it seemed as though ArcPro had done away with planar measurements, yet I found no mention of this on forums, documentation, etc. Seemed like a pretty big change. But now I'm wondering if there is something glitching with my system as you are telling me that geodesic should be an 'option' not the only choice... Thoughts? Really appreciate your insights and comments, Dan. ... View more

Hi Dan, thanks for the response.  I get what you are saying, both types of measurement are abstractions from reality. But what I'm trying to understand is whether 'planar' measurements are necessary now that ArcPro is measuring area and distance geodesically. ArcMap Desktop wasn't able to make geodesic calculations (area - disabled if only geographic coordinate systems were used in the data frame). But now, even with a projected CS in the map's display, the only option for area measurement is geodesic (which it should be because it will always be more accurate than a flattened model of the ellipse). Do you see what I'm trying to get at? 1. ArcPro doesn't seem to make planar area measurements anymore. I haven't found a way to do that, anyway. 2. If geodesic area calculations are possible (in ArcPro) then why would we use projected CS anymore??  i.e. why would I use US contiguous albers equal area conic to calculate area of the intermountain west, if I can make a geodesic area calculation?? Thanks for any feedback or insight... ... View more

I've been searching for some definitive statement that Pro had done away with planar area calculations. But when I found this question and answer, it is confounding my understanding.  I'm confused about the second point above: 2. The Calculate Geometry tool uses planar because the input data has to have a projected coordinate system. You can not do planar with just a geographic (same as the answer above).    That was the case in Desktop. But in Pro, even with the Maps's display coordinate system set to a projected CS, the only area option is geodesic. I am an instructor and want to fully understand this change.  Please clarify? ... View more