1. Convert coordinates into decimal degrees

2. Introduction
Original georefenced data often contains sexasegimal coordinates (Degree Minute Seconds). This is actually an heritage from the Sumerians and ancient babylonians

3. Introduction
Original georefenced data often contains sexasegimal coordinates (Degree Minute Seconds). This is actually an heritage from the Sumerians and ancient babylonians

4. Introduction
...while most of time GIS systems requires either decimal degrees, either metric units (UTM).
It may be relevant to convert the DMS values into decimals
Not all GIS can do this

5. 1) Parse your data
Create 6 extra columns to parse the degrees minutes seconds in separate columns

6. 1) Parse your data
Create 6 extra columns to parse the degrees minutes seconds in separate columns
This step can actually be automated by using the Excel function « Find » (to find position of a word in a text) and « Mid » (to extracts elements from words)
=> this is actually the toughest difficult part of the process are there are no standard solutions! (they change with each data structure)

7. 2) Direction from the equator
add 2 extra columns for the longitude and latitude
They will contain :
« 1 » if the latitude is North or the latitude is East
« -1 » if the latitude is South or the longitude is West

8. 3) Calculation
Add 2 extra columns that will contain the decimal coordinates for latitude and longitude

9. 3) Calculation
Go to the formula field of Excel

10. 3) Calculation
To calculate the decimal latitude you need to do the following operation:
DecimalLat=(Degrees + Minutes/60 + Seconds/3600)* 1 if North or
DecimalLat=(Degrees + Minutes/60 + Seconds/3600)* -1 is South

11. 3) Calculation
select the end column and write the following formula in the formula batr by using cell references
(e.g « B2 »: second columns second row,
« F4 »: sixths columns fourth row)

12. 3) Calculation
select the end column and write the following formula in the formula bar by using cell references
(in the example
=(E2+(F2/60)+(G2/3600))*H2)

13. 3) Calculation
Repeat the same process for the longitude (by changing the references of the column)

14. 4) Generalisation
Go to the first cell of the first row with decimal latitude and copy it (press CRTL +C at the same time)

15. 4) Generalisation
Select immediately after the latitude in the latitude in the remaining rows. Keep the left-clik button pushed and move the mouse above them

16. 4) Generalisation
Apply CTRL+V (keyboard) to apply the formula on the whole column, that will then be converted

17. 4) Generalisation
Repeat the 2 last steps for the longitude

18. 5) Conclusion
Your coordinates are now converted into decimal coordinates and ready to be exported into a GIS

19. Important! The conversion doesn’t change:
the geographical reference system
the accuracy of the data
but it could change their apparent precision
(4°20’ in DMS = in DD)
So keep the original values in your database and doculent the reference system
This is just a additional notation for the same values (to ease mathematical comparison on coordinates)