Partition Tab

Raster Factor

At line and area sources, the largest dimension of a section H_max generated by segmentation is smaller than the raster factor multiplied with the distance d of the center point of the section from the receiver. A raster factor of 0.5 is used per default:

H_max < 0.5 * d

The smaller this factor, the more sub-segments of the source/s are generated and the more computation time is required.

Procedure

Upon calculation the software checks, based on shortest distance between a receiver (or a grid point) and any source, whether the entered geometry of each source section respects the defined segmentation rule. If not, the corresponding source section is halved and the check is repeated. This continues until the defined segmentation rule is respected.

Example

Path: Examples\Configuration\Partition\raster_factor

The following example shows the segmentation of a line source of 200 m length using two different raster factors for a receiver at a perpendicular distance of 100 meters from the center of the source.

	Raster Factor 0.5 The required segment length is respected with four segments because it holds: 50 m < 125/2 m or resp. 50 m < 103.1/2 m
	Raster Factor 0.1 The required segment length causes three or four division steps resp.: - for the 6.25 m segments: 6.25 m < 100/10 m or 6.25 m < 123.2/10 m - for the 12.5 m segments: 12.5 m < 128.8/10 m or 12.5 m < 137.1/10 m

Maximum/Minimum Length of Section (m)

The maximum and minimum section length (in meters) resulting from the automatic segmentation can be specified. The entered values serve as an additional criterion besides the grid factor. By the segmentation method, no larger source segments as the maximum section length and no smaller than the minimum segment length produced.

Example

Path: Examples\Configuration\Partition\max_section_length

The following examples use a raster factor of 0.5.

	maximum length of section 1000 m (default value): In this example without any effect as all segment lengths are < 1000 m.
	maximum length of section 25 m: All source segments have segment lengths smaller than 25 m. Smaller section lengths arise depending on the raster factor.

Minimum Length of Section (%)

The minimum section length can also get specified as a percentage of the total length. If the minimum segment length is not 0% the higher value of „Min. Length of Section (m)“ and „Min. Length of Section (%)“ is used.

Note

Specifying a percentage can speed up the calculation considerably, as with extended and large-area sources less rays from sub-segments are produced.

Example

Path: Examples\Configuration\Partition\min_section_length

The subsequent examples use a grid factor of 0.5 and a maximum section length of 1000 m.

minimum section length 1 m (default) and 0%: There are 14 source segments generated with the section lengths 125, 62.5 and 31.25 m.

minimum section length 100 m and 0%: There are 12 source segments generated with the section lengths 125 and 62.50 m. The four sections having a length of 31.25 m have been replaced by two sections with a length of 62.50 m in order to fulfill the condition: 62.5 m < 100 m.

Partition according to RBLärm-92, Proc. 1

The procedure 1 is the so-called "precise" method according to RB-1992 yielding sections as long as possible.

Note

This option is just relevant to German road noise assessments.

Projection of

With the option „Projection“ activated, prior to the segmentation of sources, a pre-partitioning for line and area sources occurs subdividing the source into screened and unscreened parts. After this subdivision the screened and unscreened parts of source are segmented separately based on the distance criterion (see Projection at extended Sound Sources).

Projection at Terrain Model

With this option, even the terrain being modeled from terrain contours is considered within the projection procedure of line and area sources. This option is disabled by default.

When this option is enabled the terrain contour lines resulting from the triangulation are ignored when deciding which terrain contours provide screening or not.

Example

Path: Examples\Configuration\Partition\projection_DTM

Projection at Terrain Model OFF: The screening of the line source line by the terrain (with a top edge at 20 m height) is not considered the projection.

Projection at Terrain Model ON: In the projection, the part of the line source shielded by the terrain (orange rays) is segmented separately from the non-screened part.

Maximum Distance Source-Receiver

If the receiver point is further away than this maximum distance no projection is applied (default distance: 2000 m).

Search Radius Source

When partitioning sources using the projection only obstacles which are taken into account within this distance from the source (default radius: 100 m).

Search Radius Receiver

When partitioning sources using the projection only obstacles which are taken into account within this distance from the receiver (default radius: 100 m).

Min. Lengths are considered by projection

With activation of this option the projection method will not generate smaller sections as specified for the „Min. Length of Section“. The larger value of „Min. Length of Section (m)“ and „Min. Length of Section (%)“ will be used.

Note

Activating this option can accelerate the computation.

Example

Path: Examples\Configuration\Partition\min_section_length_projection

option „Min. Lengths are considered by projection“ ON

option „Min. Lengths are considered by projection“ OFF: The rays in orange color shown above do not occur with the option activated.