org.opentripplanner.routing.util

Class ElevationUtils

java.lang.Object

org.opentripplanner.routing.util.ElevationUtils

public class ElevationUtils
extends Object

Field Summary

Fields

Modifier and Type	Field and Description
static double	GRAVITATIONAL_ACCELERATION_CONSTANT This gravitational constant is actually dependent on latitude and height.
static double	ZERO_ELEVATION_DRAG_RESISTIVE_FORCE_COMPONENT

Constructor Summary

Constructors

Constructor and Description
ElevationUtils()

Method Summary

Modifier and Type	Method and Description
static double	getDragResistiveForceComponent(double altitude) Calculates the components of drag resistance except for the velocity assuming travel through dry earthy air.
static double	getDynamicRollingResistance(double beta) Coefficient for the dynamic rolling resistance, normalized to road inclination; CrVn = CrV*cos(β)
static PackedCoordinateSequence	getPartialElevationProfile(PackedCoordinateSequence elevationProfile, double start, double end)
static SlopeCosts	getSlopeCosts(org.locationtech.jts.geom.CoordinateSequence elev, boolean slopeLimit)
static Double	parseEleTag(String ele) checks for units (m/ft) in an OSM ele tag value, and returns the value in meters
static double	slopeSpeedCoefficient(double slope, double altitude)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

GRAVITATIONAL_ACCELERATION_CONSTANT

public static final double GRAVITATIONAL_ACCELERATION_CONSTANT

This gravitational constant is actually dependent on latitude and height. However, the amount of variation is not that much, so we just use the constant at 45 degrees of latitude. See https://en.wikipedia.org/wiki/Gravitational_acceleration#Gravity_model_for_Earth

See Also:

Constant Field Values

ZERO_ELEVATION_DRAG_RESISTIVE_FORCE_COMPONENT

public static final double ZERO_ELEVATION_DRAG_RESISTIVE_FORCE_COMPONENT

Constructor Detail

ElevationUtils

public ElevationUtils()

Method Detail

getDynamicRollingResistance

public static double getDynamicRollingResistance(double beta)

Coefficient for the dynamic rolling resistance, normalized to road inclination; CrVn = CrV*cos(β)

Parameters:

beta - Inclination angle = arctan(grade/100)

getDragResistiveForceComponent

public static double getDragResistiveForceComponent(double altitude)

Calculates the components of drag resistance except for the velocity assuming travel through dry earthy air. The equation for drag resistance and the extracted value is as follows: Fdrag = 0.5 * Cd * A * Rho * V^2 ⎣dragComponent⎦ Note that the 0.5 is accounted for as a part of the final micromobility speed calcuations. See https://www.gribble.org/cycling/power_v_speed.html The CDA is defined as a constant, but Rho represents air density which is dependent on a lot of things. The full equation is as follows: ρ = (pd / (Rd * T)) + (pv / (Rv * T)) See https://www.omnicalculator.com/physics/air-density where ρ = air density in kg/m^3 pd = air pressure in Pascals Rd = specific gas constant for dry air T = air temperature in Kelvin pv = water vapor pressure in Pascals Rv = specific gas constant for water vapor In the second half of the equation (pv / (Rv * T)), this is a calculation given the water vapor pressure. If we assume travel through dry air, this number effictively becomes 0. Therefore, this calculation is ommitted. Therefore, that leave us with: ρ = (pd / (Rd * T)) where: ρ = air density in kg/m^3 pd = the pressure of dry air in hPa, Rd = the specific gas constant for dry air T = the air temperature in Kelvins The pressure of dry air is described with the following formula: P = P0 * exp (-g * M * (h-h0) / (R * T)) See https://www.omnicalculator.com/physics/air-pressure-at-altitude where P = the air pressure in hPa P0 = is the pressure at the reference level h0 which is assumed to be 0 meters above sea level g = the gravitational acceleration constant M = the molar mass of air h = the altitude in meters at which we want to calculate the pressure R = the universal gas constant T = the temperature at altitude h P0, g, M and R are all constants. h is provided as an input parameter. And we randomly guess T by starting with a randomly guesssed temperature at sea level that is then assumed to fall 9.8°C per 1,000 meters of elevation gain. See https://www.onthesnow.com/news/a/15157/does-elevation-affect-temperature

Parameters:

altitude - The altitude in meters

getSlopeCosts

public static SlopeCosts getSlopeCosts(org.locationtech.jts.geom.CoordinateSequence elev,
                                       boolean slopeLimit)

Parameters:

elev - The elevation profile, where each (x, y) is (distance along edge, elevation)

slopeLimit - Whether the slope should be limited to 0.35, which is the max slope for streets that take cars.

Returns:

slopeSpeedCoefficient

public static double slopeSpeedCoefficient(double slope,
                                           double altitude)

getPartialElevationProfile

public static PackedCoordinateSequence getPartialElevationProfile(PackedCoordinateSequence elevationProfile,
                                                                  double start,
                                                                  double end)

parseEleTag

public static Double parseEleTag(String ele)

checks for units (m/ft) in an OSM ele tag value, and returns the value in meters