June 2025 - Roundtable

mysql GIS oddity: PointOnSurface not Contained?
by Trevor Cordes 19 Jun '25

19 Jun '25

(I lied, I'm using MariaDB 10.11.11, but it's mostly the same as latest MySQL for GIS.) I have multipolygons (1+ polygons making up 1 geometric shape). (They bound the US states.) I use ST_PointOnSurface to grab a random point on/inside one of these multipolys (using my states dataset). But when I do a ST_Contains search using that point, on the exact same geometry I used to get the point, some states are getting the result where the point is not within the state!! My whole goal is to turn a state into a point and then have that point be within the state, using existing MySQL functions. In my mind, this should ALWAYS work, instead of returning 0 rows: SELECT * FROM states WHERE ST_Contains(multipolygon, (SELECT ST_PointOnSurface(multipolygon) FROM states WHERE abbr='tx') ) I did find: https://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spa… Where the guy says Contains doesn't include the boundary of the poly itself! That would explain it. He says better/newer systems have a Cover fn which will make the above work as intended. Mysql/Maria don't seem to have that (yet?). So I tried emulating it... after all I should be able to use Intersects or something to cover the case where it's on the boundary itself. But it doesn't find a match either. I tried every function Maria offers and none will find the point ST_PointOnSurface gives me within the original multipolygons. I'm not sure why the point-on-boundary type functions like Intersects aren't finding anything. Maybe because we're dealing with a zillion decimal places, nothing is really on the boundary. I think I could use Centroid instead of PointOnSurface, but then I'd also have to yank out just 1 polygon instead of the multi, because the centroid is not guaranteed to be on the surface! And even then, a pahtological shape of the single poly (say a donut) would also have a centroid not on the surface, right? Argh... Yes, I checked the point ST_PointOnSurface returns for TX and it's legit in TX, a little farther north than the Rio Grande, in what appears to be the southernmost point of TX. If anyone has any ideas, it would make my day! Ideally an idea on how to emulate Cover would work; or ways to get a point a little more "inside" the polygon without worrying if we are still inside the polygon or not! Thanks!

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The Last Meeting,
by Sean 09 Jun '25

09 Jun '25

Hello, As I wasn't able to attend this previous meeting (the last one of the season?) I'm wondering if it is downloadable and I could watch it now? Especially interested in the RAW portion, as I didn't want to miss it. Can such a thing happen? Sean

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Systems Programming Languages User Group (C++, Rust, etc)
by Braden Ganetsky 09 Jun '25

09 Jun '25

Hi all, TL;DR: I'm looking for people who enjoy writing C++, C, Rust, Go, Zig, or any other systems programming languages. My name is Braden Ganetsky, and I run the "Winnipeg C++ Developers" user group. I am a member of the ISO C++ standards committee, and I have a keen interest in the C++ language in particular. I hold meetups approximately once a month, with an irregular cadence depending on when I am able to book a room. Our next meetup is on Thursday June 12th from 6pm to 8pm, in the program room (2nd floor) at the St. James-Assiniboia Library, 1910 Portage Ave. It is open to anyone who is interested, free of charge. If you are interested in systems programming, I would love to see you at my event! I don't yet have a website, but I do have a LinkedIn group here ( https://www.linkedin.com/groups/14382138/) A website will be in the future. Ultimately I want to broaden the group's scope to include more than just C++, including Rust, Go, Zig, or anything else of interest to the members. I'm looking for people who enjoy writing code in these sorts of languages. If that is you, please let me know. I'm looking to continue building this group to share this passion. Thank you! Braden

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Reminder: MUUG Meeting, Tonight, June 3, 7:30pm (In-person/Hybrid Meeting) -- RawTherapee, RTFM: /bin Diving
by Gilbert Detillieux 03 Jun '25

03 Jun '25

A reminder that the MUUG meeting will be this evening, both in person and online... The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting IN PERSON, on Tuesday, June 3th, at 7:30pm. Yes, that's the FIRST Tuesday of the month... RawTherapee Wyatt Zacharias has volunteered to give us a quick demo of RawTherapee. Take your photography to the next level with RawTherapee. Modern DSLR (and now mirrorless) camera sensors are capable of capturing dynamic range far beyond what a standard 8-bit JPG can display. By capturing the raw sensor data from the camera we can access up to 14 bits of dynamic range and adjust our photos non-destructively and without any loss of quality. RawTherapee provides a full suite of photo editing tools including color correction, white balance, noise and distortion correction, and many more. RTFM: /bin Diving 5.0, The Brazilian Strikes Back! Due to overwhelming meeting participation (and a little board member peer pressure), we have somehow convinced our Brazilian board member, Alberto Abrao, to take a spin at trying to figure out what a random /bin command does, live. Where to find the Meeting: Fortress Software Inc., 350 Keewatin St -- Unit #2 For one last time, we are again meeting at Brad Vokey's work office. The meeting room will be open by 7:00 pm, with the actual meeting starting at 7:30 pm. If driving, enter the lot using the most north east entrance and drive around to the south west corner of the building (see route in map detail on poster linked below). You can use any of the free, ample, and safe parking spots that say "reserved" in front of units #1 through #4 before entering unit #2. Bus stops #30814 and #30880 (route 77) are only 150 meters away. The last bus leaves for Polo Park at 10:15 pm and for Garden City at 10:31 pm. Logan Ave. bus routes #19, #26, and #27 are a 600 meter (8 minute) walk to the south. For those unable or preferring not to attend in person, the meeting will also be available online, using BBB as usual. Stay tuned to our muug.ca home page for the official URL, which will be made available about a half hour before the meeting starts. (Reload the page if you don't see the link, or if there are issues with connecting.) The group now holds its meetings at 7:30pm on the *first* Tuesday of every month from September to June. (There are no meetings in July and August.) Meetings are open to the general public; you don't have to be a MUUG member to attend. For more information about MUUG, and its monthly meetings, check out their web server: https://muug.ca/ Help us promote this month's meeting, by putting this poster up on your workplace bulletin board or other suitable public message board, or linking to it on social media: https://muug.ca/meetings/MUUGmeeting.pdf -- Gilbert E. Detillieux E-mail: <gedetil(a)muug.ca> Manitoba UNIX User Group Web: http://muug.ca/

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