Field calculator formula converting DMS coordinate to decimal

Question

I'm trying to convert DMS coordinate written as DD-MM-SS.SSS (ex. 17-42-35.244) in decimal, someone not human suggested me:

to_real(left("Field",2)) + 
to_real(mid("Field",4,2))/60 + 
to_real(right("Field",5))/3600

But QGIS says Expression is invalid.

If I consider only converting Degrees/Minutes/Seconds to_real(left("Field",2)) without any other mathematical operation, I obtain some results.

What is wrong?

hi, thanks for suggestion. I know about to_decimal but in my qgis it does not exist. Thanks again — Eppesuiga, Mar 26 at 18:08
See updated answer. You seem to have a version older than 3.16. Time to update. — Babel, Mar 26 at 19:36

Babel · Accepted Answer · 2023-03-26 19:35:50Z

to_decimal ("Field")

Example: if Field value is '17-42-35.244', the output is 17.70979

For QGIS versions older than 3.16, change your expression accordingly:

Function mid() does not exist. Use function substr() instead.
In the last line, as parameter of the right() function, you must include 6, not 5 characters. The dot counts as a character, too. With 5, you just have 5.244 instead of 35.244 as input.

So the modified expression looks like:

to_real(left("Field",2)) + 
to_real(substring("Field",4,2))/60 + 
to_real(right("Field",6))/3600

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