Question

Regex in StringSearcher to extrapolate/separate DMS (in ##° ##' ##.#####" format) for decimal degree conversion

  • 24 July 2018
  • 3 replies
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bwasserstein
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I found some help in an earlier post in regards to this (https://knowledge.safe.com/questions/46672/change-degree-minute-seconds-hemisphere-to-decimal.html), but the format of my DMS lat longs is different (I have spaces between the DMS values and my lat/long DMS values are separated). I tried to edit the regex from that post to no avail while trying to extrapolate my latitude DMS values...

(\\d+\\.?\\d*)|([NSEW])

(\\d+\\.? \\d*)|([NSEW])

(\\d+\\.? \\d*)|([NS])

However, my matched parts comes through with just the degrees value and are missing the minutes & seconds values. I will admit that I don't know enough regex!

Here's the details... I have latitude and longitude values stored in separate columns in DMS format (e.g., 27° 54' 32.32124" N or 38° 24' 16" N), and I need to convert them to decimal degrees. The seconds values may have a precision of anywhere from 2-7 with a scale of 0-5. I know I could probably handle this in a more cumbersome way with testers/testfilters and substring extractors, but I'd really like to figure out a regex expression to use in a stringsearcher and then push the matched parts values for degrees, minutes, and seconds to a DecimalDegreesCalculator. This would be a much more elegant conversion to decimal degrees.

Unfortunately I'm running a slightly older (2015) version of FME along with my organization's ArcGIS 10.3 subscription. If anyone has a regex to help make my conversion more elegant, that would be much appreciated!

3 replies

bwasserstein
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I'll answer my own question!

Was able to make this work using regex with three string searchers (each searching the lat or long DMS string for the D, M, or S values separately). I'm not certain why I couldn't get the parts list to work with just one string searcher, maybe it's a limitation with my version of FME, oh well.

The regex...

(\\d*)° to extrapolate degrees values

(\\d*)' to extrapolate mins values

(\\d+\\.\\d*)"|(\\d*)" for seconds (accounts for decimal & non-decimal seconds values)

Then the resulting three matched result attributes were pushed to a string replacer to remove the special characters using regex (°|'|"), then they were converted to decimal degrees in an attribute creator with FME math functions...

(@add(@Value(_matched_characters_LAT_D),@div(@Value(_matched_characters_LAT_M),60),@div(@Value(_matched_characters_LAT_S),3600)))

Whew :) I'm sure there's a more elegant way out there, but I feel better for forcing myself to learn regex! If anyone knows of a more elegant way I'm still happy to hear about it!

takashi
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Hi @bwasserstein, have you specified the "Subexpression Matches List Name" parameter? I think every substring that matches the sub expression will be stored in the "_sub{}.part" list, if you set the parameter like this.

0684Q00000ArKcKQAV.png

Also, this regex seems to be better.

(\d+\.?\d*|[NSEW])
takashi
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Userlevel 2
Badge +17

Hi @bwasserstein, have you specified the "Subexpression Matches List Name" parameter? I think every substring that matches the sub expression will be stored in the "_sub{}.part" list, if you set the parameter like this.

0684Q00000ArKcKQAV.png

Also, this regex seems to be better.

(\d+\.?\d*|[NSEW])
In this case, "All Matches List Name" parameter can also be available, as @david_r suggested in the previous thread.

 

0684Q00000ArMOJQA3.png

 

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