Boulder sizes

Chosen by "type" in ejecta_sizes, sizes.

Type	What it is
golombek_rapp	Golombek and Rapp boulder sizes, set by the fraction of ground the boulders cover and the layer's qa and qb.
sp8023_intercrater	Blocks between craters from NASA SP-8023, the lunar surface design model (Figure 7).
sp8023_crater	Blocks around blocky craters from NASA SP-8023 (Figure 9), for the ejecta of craters that reached bedrock.
synthterrain	One of the power-law boulder distributions synthterrain offers, for comparison with it.
power_law	A cumulative power law, N(>=D) = coefficient D^-exponent per m^2 with D in metres.
piecewise_power_law	A cumulative distribution made of power-law segments over diameter ranges.
tabulated	A cumulative distribution from a table of diameters and counts N(>=D), in units you choose.
piecewise_uniform	Counts per m^2 in diameter bands, each with diameters spread uniformly across it; none outside the bands.

golombek_rapp

Golombek and Rapp boulder sizes, set by the fraction of ground the boulders cover and the layer's qa and qb.

Every key with its default

{
    "type": "golombek_rapp"
}

sp8023_intercrater

Blocks between craters from NASA SP-8023, the lunar surface design model (Figure 7).

Key	Type	Default	Range	Unit	Description
curve	one of minimum, nominal, maximum	"nominal"			Which of the model's minimum, nominal and maximum curves to use, from fewest to most boulders.

Every key with its default

{
    "type": "sp8023_intercrater",
    "curve": "nominal"
}

Used in: example_boulders_sp8023

sp8023_crater

Blocks around blocky craters from NASA SP-8023 (Figure 9), for the ejecta of craters that reached bedrock.

Key	Type	Default	Range	Unit	Description
curve	one of minimum, nominal, maximum	"nominal"			Which of the model's minimum, nominal and maximum curves to use, from fewest to most boulders.

Every key with its default

{
    "type": "sp8023_crater",
    "curve": "nominal"
}

synthterrain

One of the power-law boulder distributions synthterrain offers, for comparison with it.

Key	Type	Default	Range	Unit	Description
model	one of intercrater, haworth, viper_specification	"intercrater"			Which of synthterrain's power-law boulder distributions to use.

Every key with its default

{
    "type": "synthterrain",
    "model": "intercrater"
}

power_law

A cumulative power law, N(>=D) = coefficient D^-exponent per m^2 with D in metres.

Key	Type	Default	Range	Unit	Description
coefficient	number	0.1	(0, inf)		Coefficient of N(>=D) = coefficient D^-exponent, the cumulative count per m^2 with D in metres; scales how many there are.
exponent	number	2.0	(0, inf)		Exponent of the power law; larger values give relatively more small craters or boulders.

Every key with its default

{
    "type": "power_law",
    "coefficient": 0.1,
    "exponent": 2.0
}

Used in: example_boulders_slope_map, example_boulders_thomas_clusters

piecewise_power_law

A cumulative distribution made of power-law segments over diameter ranges.

segments[]: Power-law segments in strictly increasing order of start, each running to the next one's start; they must meet at their joins.

Key	Type	Default	Range	Unit	Description
start	number	0.0	[0, inf)	m	Diameter in metres where this segment begins; it runs up to the next segment's start.
coefficient	number	1.0	(0, inf)		Coefficient of N(>=D) = coefficient D^-exponent, the cumulative count per m^2 with D in metres.
exponent	number	2.0	(0, inf)		Exponent of the segment's power law; larger values give relatively more small craters.

Every key with its default

{
    "type": "piecewise_power_law",
    "segments": [
        {
            "start": 0.0,
            "coefficient": 1.0,
            "exponent": 2.0
        }
    ]
}

tabulated

A cumulative distribution from a table of diameters and counts N(>=D), in units you choose.

Key	Type	Default	Range	Unit	Description
diameters	list of number	[]	(0, inf)		Table diameters in diameter units, at least two, positive and strictly increasing; counts are interpolated linearly in log D and log N between them.
cumulative	list of number	[]	(0, inf)		Cumulative count N(>=D) at each diameter, per area unit; positive and not increasing.
diameter_unit	number	1.0	(0, inf)	m	Metres per table diameter unit: 1 for metres, 1000 for km.
area_unit	number	1.0	(0, inf)	m^2	Square metres per table area unit: 1 for m^2, 1e6 for km^2.

Every key with its default

{
    "type": "tabulated",
    "diameters": [],
    "cumulative": [],
    "diameter_unit": 1.0,
    "area_unit": 1.0
}

piecewise_uniform

Counts per m^2 in diameter bands, each with diameters spread uniformly across it; none outside the bands.

Key	Type	Default	Range	Unit	Description
total	number	0.0	[0, inf)	1/m^2	Count per m^2 of all bands together, shared in proportion to each band's density; 0 uses the densities as given.

bands[]: Diameter bands with their counts; overlapping bands add, and gaps between them hold none.

Key	Type	Default	Range	Unit	Description
min	number	1.0	(0, inf)	m	Smallest diameter of the band in metres.
max	number	2.0	(0, inf)	m	Largest diameter of the band in metres, above min.
density	number	0.01	[0, inf)	1/m^2	Count per m^2 with diameters in the band, spread uniformly across it; a relative weight when total is set.

Every key with its default

{
    "type": "piecewise_uniform",
    "bands": [
        {
            "min": 1.0,
            "max": 2.0,
            "density": 0.01
        }
    ],
    "total": 0.0
}