# Geographic Coordinates¶

Contents

The GeoCoordinates object (also LATLNG) represents a latitude and longitude pair, which is a location on the surface of a Body.

## Creation¶

LATLNG(lat,lng)
Parameters: lat – (deg) Latitude lng – (deg) Longitude GeoCoordinates

This function creates a GeoCoordinates object with the given latitude and longitude, assuming the current SHIP’s Body is the body to make it for.

Once created it can’t be changed. The GeoCoordinates:LAT and GeoCoordinates:LNG suffixes are get-only (they cannot be set.) To switch to a new location, make a new call to LATLNG().

If you wish to create a GeoCoordinates object for a latitude and longitude around a different body than the ship’s current sphere of influence body, see Body:GEOPOSITIONLATLNG for a means to do that.

It is also possible to obtain a GeoCoordinates from some suffixes of some other structures. For example:

SET spot to SHIP:GEOPOSITION.


## Structure¶

structure GeoCoordinates
Suffix Type Args Description
LAT scalar (deg) none Latitude
LNG scalar (deg) none Longitude
DISTANCE scalar (m) none distance from CPU Vessel
TERRAINHEIGHT scalar (m) none above or below sea level
HEADING scalar (deg) none absolute heading from CPU Vessel
BEARING scalar (deg) none relative direction from CPU Vessel
POSITION Vector (3D Ship-Raw coords) none Position of the surface point.
ALTITUDEPOSITION Vector (3D Ship-Raw coords) scalar (altitude above sea level) Position of a point above (or below) the surface point, by giving the altitude number.
VELOCITY OrbitableVelocity none Velocity of the surface at this point (due to the rotation of the planet/moon).
ALTITUDEVELOCITY OrbitableVelocity scalar (altitude above sea level) Velocity of a point above (or below) the surface point, by giving the altitude number.

Note

This type is serializable.

GeoCoordinates:LAT

The latitude of this position on the surface.

GeoCoordinates:LNG

The longitude of this position on the surface.

GeoCoordinates:DISTANCE

Distance from the CPU_Vessel to this point on the surface.

GeoCoordinates:TERRAINHEIGHT

Distance of the terrain above “sea level” at this geographical position. Negative numbers are below “sea level.”

GeoCoordinates:HEADING

The absolute compass direction from the CPU_Vessel to this point on the surface.

GeoCoordinates:BEARING

The relative compass direction from the CPU_Vessel to this point on the surface. For example, if the vessel is heading at compass heading 45, and the geo-coordinates location is at heading 30, then GeoCoordinates:BEARING will return -15.

GeoCoordinates:POSITION

The ship-raw 3D position on the surface of the body, relative to the current ship’s Center of mass.

GeoCoordinates:ALTITUDEPOSITION

The ship-raw 3D position above or below the surface of the body, relative to the current ship’s Center of mass. You pass in an altitude number for the altitude above “sea” level of the desired location.

GeoCoordinates:VELOCITY

The (linear) velocity of this spot on the surface of the planet/moon, due to the rotation of the body causing that spot to move though space. (For example, on Kerbin at a sea level location, it would be 174.95 m/s eastward, and slightly more at higher terrain spots above sea level.) Note that this is returned as an OrbitableVelocity, meaning it isn’t a vector but a pair of vectors, one called :orbit and one called :surface. Note that the surface-relative velocity you get from the :surface suffix isn’t always zero like you might intuit because :surface gives you the velocity relative to the surface reference frame where SHIP is, which might not be the same latitude/longitude/altitude as where this Geocoordinates is.

GeoCoordinates:ALTITUDEVELOCITY

This is the same as GeoCoordinates:VELOCITY, except that it lets you specify some altitude other than the surface terrain height. You specify a (sea-level) altitude, and it will calculate based on a point at that altitude which may be above or below the actual surface at this latitude and longitude. It will calculate as if you had some point fixed to the ground, like an imaginary tower bolted to the surface, but not at the ground’s altitude. (The body’s rotation will impart a larger magnitude linear velocity on a locaton affixed to the body the farther that location is from the body’s center).

## Example Usage¶

SET spot TO LATLNG(10, 20).     // Initialize point at latitude 10,
// longitude 20

PRINT spot:LAT.                 // Print 10
PRINT spot:LNG.                 // Print 20

PRINT spot:DISTANCE.            // Print distance from vessel to x
PRINT spot:BEARING.             // Print the heading to the point

SET spot TO SHIP:GEOPOSITION.   // Make spot into a location on the
// surface directly underneath the
// current ship

SET spot TO LATLNG(spot:LAT,spot:LNG+5). // Make spot into a new
// location 5 degrees east
// of the old one

// Point nose of ship at a spot 100,000 meters altitude above a
// particular known latitude of 50 east, 20.2 north:
LOCK STEERING TO LATLNG(50,20.2):ALTITUDEPOSITION(100000).

// A nice complex example:
// -------------------------
// Drawing an debug arrow in 3D space at the spot where the GeoCoordinate
// "spot" is:
// It starts at a position 100m above the ground altitude and is aimed down
// at the spot on the ground:
SET VD TO VECDRAWARGS(
spot:ALTITUDEPOSITION(spot:TERRAINHEIGHT+100),
spot:POSITION - spot:ALTITUDEPOSITION(TERRAINHEIGHT+100),
red, "THIS IS THE SPOT", 1, true).

PRINT "THESE TWO NUMBERS SHOULD BE THE SAME:".
PRINT (SHIP:ALTITIUDE - SHIP:GEOPOSITION:TERRAINHEIGHT).