OpenStreetMap

should every OSMer be an expert in Geodesy?

Posted by maning on 5 November 2009 in English (English)

Found this from a blog comment about OSM.

"I suggest that you should invite a mapping professional into your group. Mapping is not a kiddy thing. It requires knowledge on Geometric Geodesy and GPS Systematic Errors. Without the required knowledge, doing mapping is just like wearing a blindfold blindly."

http://mapping.ideacampdavao.com/2009/07/davao-mapping-party-post-party-report.html

newbie: I want to contribute to OSM
OSM "expert": Welcome! I suggest you start reading ASPRS journals on Geodesy and GPS geometric corrections.
newbie: OH OK, bye.

Comment from Steeley on 5 November 2009 at 14:28

Ah, yes the typical specialist snob. Unfortunately there are people like this in any area of interest (be it music, sports, computing, etc).

I think it comes from a time when things such as mapping were difficult and required specialist knowledge and years of experience. With the increase in GPS and ease of use, these people still like to pretend it should be as hard for everyone as it was for them.

Either that or they just like to pretend they know something that not many people care about.

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Comment from Marco Foi on 5 November 2009 at 15:05

Indeed mapping could require lot of knowledge... ..but much depends on the task. The aim of OSM clearly cuts off all problems concerning accuracy, error correction and projection issues: no one would use our data to make reliable or mission-critical calculations. This does not mean than all OSM data is rubbish: the use of cheap consumer-GPS gives a certain degree of reliability which cannot be worse than a certain level, provided that the user can correctly operate his equipment, avoiding the main threats to the quality of his tracks (thick vegetation over paths, high cliffs or buildings hiding large amount of the sky, ...)

Marco Foi

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Comment from davespod on 5 November 2009 at 15:25

I lurve the follow up comment from the same commentator:

"Its nice to learn that you indeed have mapping professionals in your group. I also suggest that you need to at least discuss within the group the implications of Executive Order No. 45 or the PPCS-TM/PRS92 as a WGS84 variant. Good luck."

At first glance this would seem to support Steeley's viewpoint! (But maybe a well-informed reader who knows what the hell it means might explain how important it really is?)

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Comment from maning on 5 November 2009 at 15:36

> Mapping is not a kiddy thing.
I assume the premise here is "do it right the first time". While we try to always adopt this mantra. OSM was inherently designed with a big "CTRL-Z" anyone can use. That's the essence of a collaborative project.

That being said, we also need "mapping professional" to help out.

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Comment from RichardB on 5 November 2009 at 15:54

"I also suggest that you need to at least discuss within the group the implications of Executive Order No. 45 or the PPCS-TM/PRS92 as a WGS84 variant"

PRS92 and the others mentioned are very localised datums (i.e. the Philippines), which will surely be inappropriate in Europe or the Americas. OSM is a global project and the datum used (WGS84) seems a reasonable choice, given that other choices could be inappropriate elsewhere.

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Comment from lyx on 5 November 2009 at 18:01

Apparently the original comment on that blog was not from an "OSM expert", but from someone who claims to be a "mapping professional" who suggests, that "your group" (meaning the OSM project) would need mapping professionals, because mapping is a complicated thing that can only be done by experts. Looking at OSM I think I disagree; obviously a lot can be done by enthusiasts without much prior knowledge.

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Comment from slashme on 5 November 2009 at 19:17

This kind of person can sometimes be coaxed into making useful contributions even if they originally come only to point and laugh (and make marginally relevant comments in as opaque language as possible). If not, no big loss: If he's one in a million, there's 6000 others just like him.

OSM might not be doing everything right, but there's an impressive amount of professionalism happening now that the project has achieved critical mass. Now it doesn't depend on one individual, but on maintaining and supporting a core of well-informed, dedicated contributors who routinely do the impossible in their free time, and shepherding an army of well-intentioned amateurs who sporadically do their best.

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Comment from drlizau on 5 November 2009 at 20:30

We do have mapping professionals in our group. One of my sons is a contributor and about 2 weeks from his last exam for his surveying and geoinformatics degree.
I've noticed another surveyor from the US on legal-talk.
There are surely others who have qualifications as well as experience.
From what I have seen, common sense is required too.

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Comment from !i! on 6 November 2009 at 07:05

We have professionals, too.

But as you said I think professionals would make it very complicated just to get highly accurated results (that we doesn't need that way). Oh and I noticed that a lot of professional people have a very historic view on maps and how they should be drawn ;)

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Comment from davespod on 6 November 2009 at 09:24

Thanks, RichardB. I now understand a little more of why he raised this point. The blog was about mapping in the Philippines. In fact, the point he seems to be making seems to be to do with understanding the particular inaccuracy of using GPS in the Philippines, so he may be right that it would be useful for someone to explain the issue in lay terms to local mappers, so they can be aware of it (though I think they have some hi-res aerial imagery anyway). It's just a shame he made the "kiddy" comment. I think that kind of approach is always just going to switch people off.

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