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Home > Community > Featured Articles > Entering Latitude and Longitude

Entering Latitude and Longitude in the GNS530

submitted by Munro - July 22, 2003

Five alpha/numeric characters is the maximum size of the name position that allows you to define the Garmin User Waypoints. Our existing naming conventions for NDBs are two characters, VORs are three, Airports use the ICAO 4 character naming system and Intersections use 5 characters.

So the question is how to cater to the Lat/Long issue. If you want to conform to the industry standard on naming Lat/Long positions, you might find this useful.

The standard naming convention consists of four numbers and one alpha character, in either NNANN or NNNNA format. The first two numbers are the latitude in whole degrees and the second two are the longitude in whole degrees. If the longitude is 100 degrees or more the appropriate alpha character is placed between the numbers, otherwise the alpha character is positioned to the right of the four numbers.

The alpha characters used are N, E, W, and S. By choosing from the options below, you can select the northern or southern hemisphere for latitude, and the western or eastern hemisphere for longitude.

The alpha character "N" is used to select north and west co-ordinates.
The alpha character "E" is used to select north and east co-ordinates.
The alpha character "W" is used to select south and west co-ordinates.
The alpha character "S" is used to select south and east co-ordinates.

Examples:
North Lat./West Long. N520 00/W0750 00 = 5275N
North Lat./East Long. N500 00/E0200 00 = 5020E

When Long is 100 degrees or greater
North Lat./West Long. N500 00/W1550 00 = 50N55
North Lat./East Long. N050 00/E1700 00 = 05E70

South Lat./West Long. S070 00/W008000 = 0708W
South Lat./East Long. S300 00/E0200 00 = 3020S

When Long is 100 degrees or greater
South Lat./West Long. S120 00/W180000 = 12W80
South Lat./East Long. S500 00/E1100 00 = 50S10

Now we have a useable naming convention for latitude and longitude, but we still have to consider two problems:

The GPS is set up for WGS-84. This is the standard reference system for GPS and in order to get an accurate position your chart or source data should use WGS-84. If not you will typically get small position errors.
The Latitude and Longitude typically come in 3 flavors and you must be sure which system you are using again in order to get the most accurate results. For an example we will use the co-ordinates for KMIA airport.

Degrees-Minutes-Seconds (DMS) 25 ° 47 ' 35.7 " N - 80 ° 17 ' 26 " W
Decimal Degrees (DD) 25° 47.595' N - 80° 17.43333' W
Decimal Minutes (DM) 25 ° 793250 ' – (-)80 ° 290556 ' (In DM the – sign denotes either South or West)

To convert DMS to DD take the seconds and divide by 60 – 37.7/60=. 595
To convert DD to DMS take the numbers after the decimal point and multiply by 60 – .595 X 60 = 35.7
To convert DMS to DD take the minutes and divide by 60 and the seconds and divide by 3600 47/60=.7833333 and then 35.7/3600=.0099166 and add the two results together for a total of .7932499 or .793250
To convert DM to DD take the numbers after the degrees and multiple by 60 – .793250 X 60 = 47.595

Decimal Degrees is the common format used for GPS in aircraft avionics.

Creating User Waypoints:

Use the CLR key and hold for several seconds to go to the Map Page. Go to the Map page and turn the Large Knob 1 click clockwise…this will give you the WPT menu.
Now use the Small Knob and turn it clockwise to the very last position that will present you with a USR screen…if you have User Waypoints it will have “Modify?” on the screen. Regardless use this screen to create your new USR waypoint.
Push the Small Knob to activate the cursor. Use the large knob to place the cursor in the USR position.
Now use the small and large knobs to enter a name for the new waypoint and press ENT.
Your present position appears in the POSITION field at the bottom of the page. If this is the not the position you want then rotate the Large Knob to move the Cursor from the REF WPT to the Position field.
Use the Small Knob to put in the correct alpha/numeric character and the Large Knob to move the small cursor to enter the position co-ordinates for the new waypoint
Press ENT to accept the selected position
Use the Large Knob to move the cursor to the first position of the REF WPT.
Press CLR to get P.POS (Present Position) and then press ENT and ENT.
This will take you to first position on the second line of REF WPT. Again, press CLR and press ENT and ENT and ENT…the cursor should now be on CREATE…Press ENT.

Your new Lat/Long Co-ordinate has been created.

Radials or Intersection that Creates New Waypoint:

If a Lat/Long position is defined by a reference waypoint then use the identifier of the reference waypoint. The reference can be an airport, VOR, NDB or intersection that is in the database or another user waypoint.

Complete the steps 3 and 4 above to create the USER Waypoint Name and Press ENT
This will place you in the first position of the REF WPT. Using the Small and Large Knobs enter the name of the reference waypoint and Press ENT.
In the second position RAD you enter the RADIAL from the reference waypoint and press ENT.
In the third position DIS you enter the Distance from the reference waypoint and press ENT.
The second REF WPT is a temporary reference only and is not stored with the User Waypoint but used in conjunction with the first REF WPT you can create a REF Waypoint using the intersection of the two Radials. If you leave this position as is it will reference the nearest VOR.
Press ENT to move to the next field…if the Reference Waypoint information is correct you should now have the Lat/Long that you wanted….Press ENT. The cursor should now be on CREATE…Press ENT.

Your new Lat/Long Co-ordinate has been created.

After creating your User waypoint Press Menu and select “VIEW USER WAYPOINT LIST?” here you can select your User Waypoint and check them and Modify if required.