[GIS] Creating Longitude and Latitude Lines in Google Maps

distancedistance matrixlatitude longitude

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

Best Answer

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?

Related Solutions

Averaged Coordinates – How to Compute an Averaged Latitude and Longitude Coordinates

For a simple mean, you do not want to average the longitude and latitude coordinates. This might work pretty well at lower latitudes, but at higher latitudes it will begin to give poor results and completely break down near the poles.

The method I've used for this type of thing is to convert the longitude/latitude coordinates to 3d cartesian coordinates (x,y,z). Average these (to give a cartesian vector), and then convert back again. Note that you probably do not need to normalize the vector, so the actual average process could be a simple sum.

Edit, here is my c# code:

The following converts cartesian coordinates to latitude/longitude (in degrees): Remove the RAD2DEG constants for radians.

Latitude = MPUtility.RAD2DEG * Math.Atan2(z, Math.Sqrt(x * x + y * y));
Longitude = MPUtility.RAD2DEG * Math.Atan2(-y, x);

And here we calculate cartesian coordinates from latitude/longitude (specified in radians):

private void CalcCartesianCoord()
{
    _x = Math.Sin(LatitudeRadians) * Math.Cos(LongitudeRadians);
    _y = Math.Sin(LatitudeRadians) * Math.Sin(LongitudeRadians);
    _z = Math.Cos(LatitudeRadians); 
}

Both are cut & pasted from real code, hence the mix of degrees and radians. There are properties here which do some of the conversions (eg. LatitudeRadians is a property that returns a radian value).

Note that optimization is possible: the duplicate sine calculations, for instance. Also the trig calculations might be cacheable if you call them a lot.

[GIS] Countries’ Latitude and Longitude range

Yes. It is possible to get lat/long range for each country. The minimum and maximum lat/long is available at the below link. Hope this helps. https://web.archive.org/web/20150319012353/http://opengeocode.org/cude/download.php?file=/home/fashions/public_html/opengeocode.org/download/cow.txt

Best Answer

Related Solutions

Averaged Coordinates – How to Compute an Averaged Latitude and Longitude Coordinates

[GIS] Countries’ Latitude and Longitude range

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