LCZ Classification

Note

To get more informations about the method used for LCZ classification, please see the corresponding article on the References page. Note that in the manuscript, the uniqueness indicator was only valid for some of the LCZ types. It is now valid for all classes.

GeoClimate computes the Local Climate Zones (LCZ) at the RSU’s scale.

The LCZ, introduced by Stewart & Oke (2012, 2014), is a classification scheme used to segment the climate areas of cities (and other).

Methodology

A LCZ type is assigned to a RSU. This “assignment” is performed according to 14 indicators:

  • 7 indicators usually used for LCZ classification:
    • math:

      SVF : sky_view_factor

    • math:

      H/W : aspect_ratio

    • math:

      F_B : building_surface_fraction

    • math:

      F_I : impervious_surface_fraction

    • math:

      F_P : pervious_surface_fraction

    • math:

      H_r : height_of_roughness_elements

    • math:

      z_0 : terrain_roughness_class

  • 7 additionnal indicators:
    • math:

      F_B : all vegetation fraction

    • math:

      F_W : water fraction

    • math:

      F_{HV} : fraction of all land (except building, water and impervious) being high vegetation

    • math:

      F_{IND/B} : fraction of building being industrial

    • math:

      F_{LLR/B} : fraction of building being large low-rise

    • math:

      F_{RES/B} fraction of building being residential

    • math:

      N_{lev} : area weighted average number of building levels

The classification to a given type follows the procedure illustrated on the Figure below. .. figure:: /_static/image/LczProcedure.png

Each land cover type LCZ is classified according to a given set of indicators and threshold. The same apply for LCZ built types 8 and 10. A unique LCZ type (LCZ_PRIMARY) is associated to each RSU and LCZ_UNIQUENESS_VALUE is calculated to characterize the degree of certainty of the classified RSU. This calculation is unique per LCZ type:

  • LCZA: :math: 0.25 * (F_{B_{LC-max}} - F_B) / F_{B_{LC-max}} + 0.25 * (H/W_{B_{LC-max}} - H/W) / H/W_{B_{LC-max}} + 0.5 * (F_{HV} - F_{B_{LC-max}) / (1 - F_{B_{LC-max})

  • LCZB: :math: 0.25 * (F_{B_{LC-max}} - F_B) / F_{B_{LC-max}} + 0.25 * (H/W_{B_{LC-max}} - H/W) / H/W_{B_{LC-max}} + 0.25 * (F_{AV} - F_{B_{LC-max}) / (1 - F_{B_{LC-max}) + 0.25 * ((F_{HV/AV_{max}} - F_{HV/AV_{min}}) / 2 - |F_{HV/AV} - (F_{HV/AV_{max}} - F_{HV/AV_{min}}) / 2|) / ((F_{HV/AV_{max}} - F_{HV/AV_{min}}) / 2)

  • LCZD: :math: 0.25 * (F_{B_{LC-max}} - F_B) / F_{B_{LC-max}} + 0.25 * (H/W_{B_{LC-max}} - H/W) / H/W_{B_{LC-max}} + 0.5 * (F_{LV} - F_{B_{LC-max}) / (1 - F_{B_{LC-max})

  • LCZE: :math: 0.25 * (F_{B_{LC-max}} - F_B) / F_{B_{LC-max}} + 0.25 * (H/W_{B_{LC-max}} - H/W) / H/W_{B_{LC-max}} + 0.5 * (F_{I} - F_{B_{LC-max}) / (1 - F_{B_{LC-max})

  • LCZG: :math: 0.25 * (F_{B_{LC-max}} - F_B) / F_{B_{LC-max}} + 0.25 * (H/W_{B_{LC-max}} - H/W) / H/W_{B_{LC-max}} + 0.5 * (F_{W} - F_{B_{LC-max}) / (1 - F_{B_{LC-max})

  • LCZ8: :math: 0.25 * (F_{LLR/B} - F_{LLR/B_{min}}) / (1 - F_{LLR/B_{min}})

  • LCZ10: :math: 0.25 * (F_{IND/B} - F_{IND/B_{min}}) / (1 - F_{IND/B_{min}})

where :math: F_{B_{LC-max}} and :math: AR_{B_{LC-max}} are the maximum value accepted for a land cover, for building fraction and aspect ratio, respectively :math: F_{HV/AV_{min}} and :math: F_{HV/AV_{max}} are the minimum and maximum :math: F_{HV/AV} thresholds for being LCZ102

For the rest of the built types, their classification is based on the usual 7 indicators used to define LCZ classes. The method to find the most appropriate LCZ type for a given RSU is based on the minimum distance (MIN_DISTANCE) to each LCZ in the 7-dimensional space. To calculate this distance, each dimension is normalized according to the mean and standard deviation (or median and absolute median deviation) of the interval values.

Some indicators may be more important (or reliable) than others for LCZ identification. To account for this, a map of weights may be applied to multiply the distance contribution of each indicator. The default values are 4 for sky view factor, 3 for aspect ratio , 8 for building surface fraction, 0 for impervious surface fraction , 0 for pervious surface fraction , 6 for height of roughness elements, and 0.5 for terrain roughness class.

The distance of each RSU to each LCZ type is calculated in the normalized interval space. The two LCZ types closest to the RSU indicators (LCZ_PRIMARY and LCZ_SECONDARY) are assigned to this RSU.

Three indicators describe the degree of certainty of the allocated LCZ class:

  • MIN_DISTANCE: Distance from a RSU point to the closest LCZ type (lower means more certain LCZ_PRIMARY).

  • LCZ_UNIQUENESS_VALUE: Indicates certainty of the primary LCZ type (closer to 1 means more certain). Defines as (DISTANCE LCZ_PRIMARY - DISTANCE LCZ_SECONDARY) / (DISTANCE LCZ_PRIMARY - DISTANCE LCZ_SECONDARY)``

  • LCZ_EQUALITY_VALUE: Indicates whether the RSU’s LCZ could be any LCZ type (closer to 0 means more certain).

The source code is available at

Output LCZ layer

Field name

Field type

Definition

ID_RSU

integer

RSU’s unique id

LCZ_PRIMARY

integer

Main LCZ type

LCZ_SECONDARY

integer

Secondary LCZ type

MIN_DISTANCE

double precision

Minimum distance to each LCZ. Only valid for LCZ1 to LCZ7 and LCZ9.

LCZ_UNIQUENESS_VALUE

double precision

Indicates how unique (and thus how certain) is the attributed LCZ type.

LCZ_EQUALITY_VALUE

double precision

Indicates whether the LCZ type of a RSU could be any LCZ type. Based on distance calculation in the 7 dimension space, thus only valid for LCZ1 to LCZ7 and LCZ9.

LCZ_PRIMARY and LCZ_SECONDARY Column Values

Each LCZ value is encoded using the following type codes.

For each, the LCZ class name and hexadecimal color code (for map styling) are given. The default .sld file format can be downloaded at this address.

Type

Type definition

Hexa Color code

1

LCZ 1: Compact high-rise

#8b0101

2

LCZ 2: Compact mid-rise

#cc0200

3

LCZ 3: Compact low-rise

#fc0001

4

LCZ 4: Open high-rise

#be4c03

5

LCZ 5: Open mid-rise

#ff6602

6

LCZ 6: Open low-rise

#ff9856

7

LCZ 7: Lightweight low-rise

#fbed08

8

LCZ 8: Large low-rise

#bcbcba

9

LCZ 9: Sparsely built

#ffcca7

10

LCZ 10: Heavy industry

#57555a

101

LCZ A: Dense trees

#006700

102

LCZ B: Scattered trees

#05aa05

103

LCZ C: Bush, scrub

#648423

104

LCZ D: Low plants

#bbdb7a

105

LCZ E: Bare rock or paved

#010101

106

LCZ F: Bare soil or sand

#fdf6ae

107

LCZ G: Water

#6d67fd

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