check precision of site coordinates

[teixeirak]

@Troger4 , here are instructions for checking the precision of site coordinates. Please try these out and let me know if they make sense to you. If you have any doubts, please ask before proceeding.

1. ensure that you've pulled the latest version of ForC, then open ForC_sites
2. focus on the column coordinates.precision (K in Excel)
3. find any site with NAC in this field, then find the study/ studies with records at this site in measurement.refs. There may be additional info on the site in site.refs. It would also be valuable to check the original source of anything with (minutes) in this field, as that indicates that current precision is very low (and hopefully the original source has something better). Open reference (you already know how to link citation.ID to pdf). If there's more than one, it may be helpful to look at more than one, but don't go overboard if there are tons of references.
4. Find the site description for a site with a name corresponding to (but not necessarily exactly matching) the one you're working on (usually near beginning of methods, but could be in table or maybe even supplementary info), specifically geographic coordinates.

converting degrees-minutes-seconds to decimal degrees:

• Decimal degrees = Degrees + (Minutes/60) + (Seconds/3600)
• for latitude, N = positive, S= negative
• for longitude, E= positive, W= negative
• if you're not confident about part of this, google for further guidance.

5. verify that coordinates entered in ForC match those given in the paper. If they don't match, please correct.
6. in coordinates.precision , enter the precision reported in the original pub (which should now match what's in ForC). Please enter exactly one of the following (parts in bold):

• degree- rounded to nearest degree or rough fraction of a degree (e.g., .167, .25, .33, .5, .67, .75, .83, or to just one decimal point);
• minute- reported to the nearest minute in original source (increments of 0.01667);
• second- reported to the nearest second in original source;
• fraction of second - reported to fraction of second in original source;
• decimal degrees to [n] digits- reported in decimal degrees to n digits (where n is minimum precision of the two coordinates);
• other (see geography.notes) - unusual cases (e.g., composite of multiple sites), as detailed in geography.notes.

7. If you run into a case that doesn't make sense, skip it and make a note that it requires review.
8. If the study has multiple sites and you can confidently link those to others reported in the study, it will be most efficient to get all those sites at the same time. You can identify them by filtering the measurement.refs field for the citation.ID you're looking at.

[Troger4]

I'll try it out today and get back to you if I have any issues. Thanks very much for the written instructions!

[teixeirak]

@ValentineHerr , it would be helpful if you could write a script (quick, I think) to flag low-precision coordinates for review. We want to identify records at the poorest level of precision:

degree- rounded to nearest degree or rough fraction of a degree (e.g., .167, .25, .33, .5, .67, .75, .83, or to just one decimal point)

What I envision is a script that looks at lat and lon and tests whether both coordinates meet that criteria. When that is the case, fill the coordinates.precision field with "(degree)" ONLY IF if it's current value is "NAC".

[ValentineHerr]

@teixeirak,

Here are an example for each case we have (where precision is "NAC" and we have coordinates). the first 2 columns are the coordinates in SITES, the 2 last columns are the number of decimals:

To confirm what you are asking, I'll enter "degree" in column coordinates.precision if min(ndec_lat, ndec_lon) <= 3, correct?

[teixeirak]

Well, it's not quite so simple as looking at n decimals, because sometimes a very rough coordinate could have high n decimals. For example, if coordinates are rounded to the nearest 10 minutes, you could get repeating values after the decimal (e.g., 30°40' --> 30.6666667). I guess the rule I'd apply is:

min(ndec_lat, ndec_lon) <= 1

OR

decimal portion = .25, .75

OR

decimal portion = .167 (1/6), .33 (1/3), .67 (2/3), or .83 (5/6), where there could be any number of repeats in the 6 or 3 (e.g., we'd count .33, .333, .3333, .33333, etc.).

[ValentineHerr]

Ok, I think I got it... but does it seem right that this would be 1788 sites?

Also, I'll be adding "(decimal)" so that @Troger4 can change to "decimal" when she checked, right? see this comment

[teixeirak]

but does it seem right that this would be 1788 sites?

Yikes, that's a lot--roughly 1/3! I didn't expect the number to be that high. If that's the case, maybe make two categories:

1. "(degree)"

min(ndec_lat, ndec_lon) =0

OR

decimal portion = .25, 0.5, .75

2. "(minutes rounded)"

doesn't meet criteria above

AND

min(ndec_lat, ndec_lon) <= 1

OR

decimal portion = .25, .75

OR

decimal portion = .167 (1/6), .33 (1/3), .67 (2/3), or .83 (5/6), where there could be any number of repeats in the 6 or 3 (e.g., we'd count .33, .333, .3333, .33333, etc.).

[teixeirak]

Also, I'll be adding "(decimal)" so that @Troger4 can change to "decimal" when she checked, right? see this comment

This doesn't make sense, unless you meant "(degree)". If that's what you meant, the answer is yes.

[ValentineHerr]

This doesn't make sense, unless you meant "(degree)". If that's what you meant, the answer is yes.

Yes, sorry, that is what I meant.

And ok for th rest, I make the change

[teixeirak]

Okay. Note that I just made a couple small edits above (so use that, not the email).

[ValentineHerr]

did you really mean min(ndec_lat, ndec_lon) =0 and not min(ndec_lat, ndec_lon) <=1 ? that reduces a lot of the issues (down to 429)

[teixeirak]

Yeah, I'd like to separate out the ones rounded to the nearest degree or quarter degree from those rounded to the nearest ten minutes or tenth of a degree. The former could easily fall in the wrong geographic.area.