Attachment A.pdf
PDF 432 KB Posted
- Attached to
- BICYCLE & PEDESTRIAN TRAVEL DATA/METRICS
- Solicitation number
- 5400022033
- Issued by
- Richland County, South Carolina
About this file
This is a technical specification document for the South Carolina Department of Transportation (SCDOT) related to a Bicycle & Pedestrian Travel Data/Metrics contract opportunity. The document provides detailed instructions for conflating and processing SCDOT's network GIS files, specifically the Statewide Highways and Statewide Other Roads datasets available through SCDOT's GIS Mapping portal. The contractor must preserve all existing Linear Referencing System (LRS) identifiers assigned to numbered routes within each county while recalculating begin mile point (BMP) and end mile point (EMP) measures according to specified methodology. Route segments are defined by true intersections with other routes or changes in street name, with all mileage calculations standardized to three decimal places to maintain data integrity and consistency across the network.
The specification establishes a precise mathematical approach for introducing breaks into existing segments when attribute changes occur, requiring calculations based on geometric length percentages rather than simple additive methods. When a segment must be subdivided due to an attribute change such as speed limit modifications, the contractor must calculate the break point by dividing the geometric distance to the break by the total segment geometry length, multiplying this percentage by the original recorded segment length, and adding the result to the original BMP to determine the new EMP and BMP values. The document emphasizes that the integrity of the entire original mileage for each segment must be preserved throughout the conflation process, with all changes occurring only at newly introduced break points rather than altering the original beginning and end values.
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Other files
| File | Type | Posted |
|---|---|---|
| Revised Award Date.pdf | ||
| Price Information.xlsx | XLSX spreadsheet | |
| Notice Regarding Award.pdf | ||
| Solicitation.pdf | ||
| Attachment B.pdf | ||
| Amendment 1.pdf |
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Text version
The original SCDOT Network has to be used for conflation process. This network GIS Files can be found here
(http://info2.scdot.org/GISMapping/Pages/GIS.aspx) - Statewide Highways and Statewide Other Roads. The two files can be combined into one. The files contain routes that have LRS identifier assigned (that has to be preserved without changes) as well as measures (BMP and EMP – which can be recalculated to a degree following the rules described below). A unique LRS is assigned per each numbered route within each county. Each LRS route is broken into segments at every true intersection with another route (state maintained or local), or where route changes street name. Each segment is assigned begin mile point and end mile point per construction plans (not per linework geometry).
When introducing a new break in the segment - Beginning and/or end mileage attributes must be re-calculated, but the integrity of the entire original mileage for the segment must be kept. All mileage calculations are out to 3 decimal places (ex: 1.234).
The original beginning and end mileage values need to be retained and the changes should occur at the breaks.
EXAMPLE: One of the original segments of SC 1 in York County runs from BMP 1 to EMP 3. So the recorded length is
2 miles (which differs a little from the geometry length of the segment, which is 1.95). Graph A below.
It is identified that about 1.6 geometric miles from the beginning of the segment Speed Limit attribute changes from
45 mph to 35 mph. This requires an introduction of a break at that point. New EMP and BMP at the break point need to be calculated for the two newly created segments (Graph B).
It cannot be simply identified as 2.6 (original BMP 1.000 plus 1.6). It has to be calculated using the percentage reference: Route Segment 1 geometry length is 1.6 miles is divided by 1.95. Result indicates that Segment 1 will keep 82% of the recorded mileage for that route.
0.82 is multiplied by the original Recoded Length (2 miles) – the result is 1.64 mi and this number is added to the
Original BMP of the segment (1.0) to identify the recorded mile point for where the attribute changes - 2.64mi (the new EMP for the first segment, as well as a new BMP for the second Segment 2). Graph C for the final results.
File details come from the government source that posted it. Updated .