2.5 Red surveys
Red surveys are detailed sketch maps of the path, with target notes about the route and the work required to bring it into good condition. The sketch maps are created using a standard format and a full set of hieroglyph symbols, describing everything from large boulders to pitched liners for cross-drains. Red surveys are the most detailed of the three levels of path survey: they are made up of intricate sketches of the path as it is now and how it will look after completion of work.
Red path surveys provide:
- a pictorial assessment of the current path condition;
- a pictorial description of work required;
- a written description of work required;
- an estimate of the time and cost to bring the path into good condition.
Red surveys are often used on site to direct work in progress. They need to contain enough detail to identify every item of work required on the route.
Carrying out a Red survey
The key features for carrying out a Red survey are listed below.
Each path comprises sections, which should be easily identifiable by reference to physical features, such as burn crossings, rocky outcrops, prominent boulders. If no suitable features are present, mark the start and end of sections with discretely located wooden pegs or canes.
Path sections are numbered consecutively from the start point, and path length is measured using a measuring wheel. Provide a grid reference at distinct features, such as burns or dykes. It should be possible for future users of the survey information to locate the start and end points of sections in the field. In the office, mark the route of the path and location of path sections on a 1:25,000 or 1:10,000 map. If the path sections are too small to show individually, then arrange them into sets of sections. Dividing the path into shorter subsection lengths tends to provide more detailed and prescriptive information.
The scale of the pictorial representation is elastic. One survey sheet may represent 500 m or 50 m. The scale depends on the complexity of the path section, the condition of it and the amount of work that is required. The scale may also vary on individual survey sheets. Both section length and cumulative length should be recorded for ease of reference. Path length or cumulative distance is normally measured using a measuring wheel such as a Trumeter.
A sketch map is made with current path condition and work required in two separate columns. All the information on the survey sheet should be entered and read from the bottom of the page to the top. A standard set of symbols is used to represent various physical characteristics and prescriptive treatments. Written notes providing information about gradient, current width, visitor behaviour, etc. can be included. Include information about availability of materials on site that could be used for path repair. If possible comment on the location and suitability of aggregate for the path base and surface, pitching stone, block stone for drain construction, and so on.
A pictorial representation is provided of work required alongside the ‘current condition’ column. A brief written description is provided in the following column, which can be expanded upon in the bill of quantities.
It may be useful to include cross-sections of path construction to clearly illustrate dimensions and path setting. Similarly, it might be useful to include cross-sections of drainage features (including dimensions) such as crossdrains, water bars and ditches.
Bill of quantity
The bill of quantity should provide a detailed written description of individual items that have been specified and the number or quantity of each item. Materials that are to be used should be specified and dimensions included.
Estimate the length of time that the work will take to complete.
Clearly state whether your time estimates are for the work to be undertaken by hand or with the aid of an excavator. If an excavator is to be used, clearly show how much it will cost and how long it will be on site.
Note the assumptions made about the movement of materials around the site. State whether this includes the use of power barrows, tracked dumpers or air-lifting material. Any additional cost involved in hiring or chartering this equipment should be included in cost calculations.
Clearly state whether materials are to be imported to the site. Importing materials will usually reduce the number of work days required to complete work. Remember to include the cost of materials and any additional transport costs in your calculations.
Technical surveying instruments such as theodolites and distomats are not required for this type of survey: the most useful tool is a good pair of eyes and attention to detail. Surveyors should be equipped with a measuring wheel, a clinometer to measure gradient along and across the path, and a tape measure. A GPS should be used to generate accurate grid reference information. If this is not available, a map and a compass will suffice. Information is collected in the field using a survey sheet. Waterproof copies of survey sheets are very useful and a clipboard is essential.
- Specify appropriately: Path repairs should reflect the terrain which they cross. Do not over-engineer paths in a rugged mountain environment. Always maintain the informal nature of upland paths.
- Use appropriate materials: Identify the appropriate sources for materials available on site if possible. If this is not practicable or appropriate ensure that imported materials match those on site.
- Realign if necessary: Evolved path lines that climb directly uphill are associated with numerous management problems. It may be possible to realign a path to reduce the gradient and make it more attractive to walkers and less intrusive, allowing the original line to recover.
- Be aware of budgets: If budgets are limited, identify priority sections and ensure that specifications are prepared for those sections first. There is little point wasting resources preparing specifications that are unlikely to happen in the near future. Remember, a specification survey will have a shelf-life of no more than 3 years.
- Employ suitably experienced and qualified staff: Red surveys rely to a large extent on the judgement and experience of the surveyor. Surveyors should have extensive experience of path development processes and path repair techniques.
- Surveyors are not infallible: Specifications are based on one or two visits to a site. Modifications may be required to specifications as work progresses and a contingency plan should allow for this.
knoll or bank
burn or other watercourse
seepage or waterflow
wet path surface
rough path surface
aggregate with geotextile
aggregate with anchorbars
turf islands or hags