![]() ![]() ![]() Or if you have some level professional GPS has Altitude H ( msl,heigh above mean sea level) and UNDULATION,the relationship between the geoid and the ellipsoid (m) of the chosen datum output from internal table. ![]() This is done by interpolating a grid of the geoid height file with a spatial resolution of 15 arc-minutes. The MSL height has to be converted to height h above the WGS 84 ellipsoid by using the geopotential model EGM96 ( Lemoine et al, 1998). Usually GPS will give us H of above MSL height. Please notice that the h is altitude above the WGS 84 ellipsoid. Public Function GetSphericalLatitude(ByVal GPSLatitude As Double, ByVal h As Double) As Doubleĭim A As Double = 6378137 'semi-major axisĭim f As Double = 1 / 298.257223563 '1/f Reciprocal of flatteningĭim Rc As Double = A / (Sqrt(1 - e2 * (Sin(GPSLatitude * PI / 180) ^ 2)))ĭim p As Double = (Rc + h) * Cos(GPSLatitude * PI / 180)ĭim z As Double = (Rc * (1 - e2) + h) * Sin(GPSLatitude * PI / 180)ĭim SphericalLatitude As Double = Asin(z / r) * 180 / PI 'Input GPSLatitude is WGS84 Latitude,h is altitude above the WGS 84 ellipsoid I attached a VB code I wrote: Imports System.Math You can use a 3-D coordinate transformation function like geodetic2enu to convert latitude. This approach requires you to select a CRS which is appropriate for the region of your data. The GPS coordinates are presented in the infowindow in an easy to copy and paste format. You can use projfwd to convert latitude-longitude coordinates to x and y map coordinates in a projected coordinate reference system (CRS) returned by projcrs. As soon as you modify one end of the data (either the decimal or sexagesimal degrees coordinates), the other end is simultaneously updated by the coordinates converter, as well as the position on the map. Reciprocal of flattening is 298.257223563. This tool is all about GPS coordinates conversion.Latitude need be converted by WGS 84 ellipsoid parameters semi-major axis is 6378137 m, and.Longitude in GPS(WGS84) and Cartesian coordinates are the same.Theory for convert GPS(WGS84) to Cartesian coordinates Regarding, the "Haversine Formula" it is easy to implement and is nice because it is using "Spherical Trigonometry" instead of a "Law of Cosines" based approach which is based on two-dimensional trigonometry, therefore you get a nice balance of accuracy over complexity.Ī gentleman by the name of Chris Veness has a great website that explains some of the concepts you are interested in and demonstrates various programmatic implementations this should answer your x/y conversion question as well. Think "which point is closest?" scenarios where you don't need a precise distance measurement. For example, the result calculated from "Manhattan Distance Formula" versus the result from the "Distance Formula" can be better for certain situations as it is computationally less expensive. I understand where starblue is coming from, but good software engineering is often about trade-offs, so it all depends on the accuracy you require for what you are doing. If you require a more rigidly WGS-84 compatible approach checkout the "Vincenty Formula." You will always have some amount of error unless you're talking about a distance of a few feet and even then there is theoretically curvature of the Earth. Yes, WGS-84 assumes the Earth is an ellipsoid, but I believe you only get about a 0.5% average error using an approach like the "Haversine Formula", which may be an acceptable amount of error in your case. "Haversine Formula" on WGS-84 data, which is a derivative of the "Law of Haversines" with very satisfying results. A user account is not needed for the features on this web page. The utm converted latitude number looks roughly close but the longitude number is way off.I have recently done something similar to this using the USA Topo Map Other Help Convert Coordinates - Calculate a position in a variety of formats. I have tried a python based utm conversion of my lat,longs which goes something like this: utm.from_latlon(25.77,-80.21) Looking at the contents of the shape file this region is roughly at a y,x coordinate of 292000, 8930000. The shape file was generated by the US government and I doubt it has any peculiar definitions (details below).Īs an example, a point in Miami, Florida has real lat,long of 25.77,-80.21. I'm trying to figure out where a given latitude, longitude coordinate should appear on a particular shape file. ![]()
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