# Creating Longitude and Latitude Lines in Google Maps

I'm working on an independent high school project where i'm trying to build a simple differential equation model for diffusion. I'm trying to overlay the model on top of a map to visualize spread, so for example, oil in water.

Right now I have a rectangular box that have the coordinates of ( 31.0195,-102.8072) NW, (19.2019, -102.8072) SW, (31.0195, -75.3963) NE, and (19.2019, -75.3963) SE. I am trying to build a 2D array of lat/long coordinates spaced evenly. For example, an array of lat/long coordinates that are 500m apart.

Is there a formula/algorithm where I can convert these coordinates to a distance, break the distance up into 500m chunks, and then get lat/long coordinates along the way (i.e. so I have lat/long coordinates every 500m)?

Thanks

• Welcome to GIS.SE. I've given a general answer below, but if you need more specifics, you'll probably need to provide even more details than you have already. You can use the edit button. May 21, 2014 at 0:32

As you're dealing with a very large curved region, you cannot get an array that has regular intervals in both angular units (degrees Lon-lat) and linear units (meters E-N).

The topic of map projections concerns this mapping of the curved earth to a flat map, and hence geographic coordinates (lon-lat) to map coordinates (E-N).

The topic of spherical geometry concerns conversion between geographic coordinates and linear distances.

This question may help: calculating distance between two latitude-longitude points.

Things to consider:

Do you want fixed linear intervals (not really compatible with what you're starting out with), or a fixed number of intervals and hence fixed angular intervals?

Depending on that, you may need to calculate the three side lengths of the "rectangular" box? The N-S lengths of the left and right sides are the same, while the E-W lengths of the top and bottom are different.

Do you have any restrictions on software you can use?