# NOAA Magnetic Field Component Grid Calculator Help

I am using NOAA's magnetic field component grid calculator trying to calculate the magnetic declination of the entire United States (here's the help page).

Essentially, the link asks for a minimum and maximum lat-lon for the grid you want to calculate the magnetic declination for. According to the help page:

The grid calculator allows for calculation of magnetic field values for an area or a point. In order to calculate a grid of components for an area, you fill out min and max longitude and min and max latitude values in order to define a bounding box for the area of interest.

`To input an area:`

``````Max longitude = 85 1 39.6192 W
Min longitude = 125 1 39.6192 W
Lon Step Size = 1.0
Max latitude = 60 3 3.7836 N
Min latitude = 20 3 3.7836 N
Lat Step Size = 1.0
``````

I am not sure what the correct "bounding box" for the entire United States is. I used an open-source tool called Bounding Box Tool, but it didn't help. Someone posted on Quora and said the "extent" of the bounding box was:

`Extent: (-124.848974, 24.396308) - (-66.885444, 49.384358)`

But... I'm not sure what that means.

Can someone help?

• What information are you looking for? What research have you done on your own? Using links as critical pieces of questions and answers are frowned upon in this community because links change often and without notice. Please take the community tour to get a better feel for what we are looking for in a question: gis.stackexchange.com/tour – MaryBeth Aug 7 '17 at 17:36
• @MaryBeth Okay, I edited the question. Hope it makes more sense now – John Lexus Aug 7 '17 at 17:49
• `Extent: (-124.848974, 24.396308) - (-66.885444, 49.384358)` are `xmin`, `ymin`, `xmax` and `ymax`. `x` is longitude and `y` is latitude in `DDD.dddd` format – aldo_tapia Aug 7 '17 at 19:31
• The Quora extent is for the lower 48 states ("conus", contiguous US). – mkennedy Aug 8 '17 at 2:45